Improvements related to internal combustion engines

Abstract

This disclosure relates to an ammonia-fueled internal combustion engine system. The engine system includes a decomposition device, which is connectable to an ammonia fuel source and configured to produce a decomposed fuel, comprising a mixture of nitrogen and hydrogen, by decomposing ammonia fuel supplied by the ammonia fuel source during engine operation. The engine system further includes a main combustion chamber and an intake port and an exhaust port, respectively, which are in fluid communication with the main combustion chamber. A secondary combustion chamber is in fluid communication with the main combustion chamber via at least one orifice, and the secondary combustion chamber further includes a decomposed fuel inlet to allow the introduction of the decomposed fuel supplied from the decomposition device into the secondary combustion chamber. An ignition device is operably positioned with the secondary combustion chamber and is configured to ignite the decomposed fuel in the secondary combustion chamber. The secondary combustion chamber and / or orifice are configured to generate a stream of combustion fluid from the secondary combustion chamber to the main combustion chamber via the orifice when the decomposed fuel is ignited in the secondary combustion chamber, in order to allow ignition of the fuel present in the main combustion chamber. The engine system further comprises a sensor arrangement configured to measure the characteristics of the decomposed fuel, and an electronic control device that communicates with the sensor arrangement and the ignition device. The electronic control device is configured to use the measurements received from the sensor arrangement to evaluate the characteristics of the hydrogen present in the decomposed fuel, and to control the introduction of the decomposed fuel into the sub-combustion chamber according to the evaluated characteristics of the hydrogen.

Description

Priority Cross-Reference

[0001] This application claims priority from Australian Provisional Patent Application No. 2023901756, filed on 2 June 2023, and Australian Provisional Patent Application No. 2024900851, filed on 28 March 2024, the contents of which are incorporated herein by reference.

Technical Field

[0002] The present disclosure generally relates to internal combustion engines, related apparatus, methods, and control systems. Specifically, the present disclosure relates to an internal combustion engine comprising a main combustion chamber and a secondary combustion chamber (or “sub-chamber”) configured to facilitate combustion of fuel within the main combustion chamber.

Background Art

[0003] The following discussion of the background of the present disclosure is intended to facilitate an understanding of the present disclosure. However, it should be understood that this discussion is not an admission or acknowledgement that any of the materials referred to were known, published, or part of common general knowledge as of the priority date of the application.

[0004] Currently, in major countries, there is a need to reduce the use and dependence on fossil fuels for energy production more than ever. CO2 emitted into the atmosphere from the combustion of fossil fuels is widely reported to increase global warming, which is expected to cause an increase in average temperature and have an adverse effect on the climate. The transport sector alone contributes a significant portion of the CO2 emissions from the combustion of fossil fuels in internal combustion engines.

[0005] Ammonia can be an excellent zero-carbon fuel for internal combustion engines. Ammonia is one of the most widely produced chemicals in the world and is used in a variety of applications, including fertilizers, cooling, and chemical processing. As a hydrogen (H2) carrier fuel, liquid ammonia has approximately 1.5 times the energy density of liquid hydrogen and can be liquefied at a relatively low pressure of about 10 bar. This makes large-scale storage and transport of ammonia significantly easier compared to hydrogen fuel. As a result, ammonia-fueled internal combustion engines may be more suitable for certain applications, or otherwise preferred over hydrogen-fueled internal combustion engines. In addition, ammonia can be produced entirely from renewable energy sources.

[0006] However, ammonia generally exhibits poor flammability as a fuel in internal combustion engines compared to hydrogen fuel. Ammonia has a relatively low flame velocity for spark-ignition engines and a relatively high autoignition temperature for diesel engines. This makes robust ignition and combustion of ammonia difficult under a wide range of engine operating conditions.

[0007] When used in spark-ignition engines, ammonia (or even mixtures of ammonia with fuels like gasoline) exhibits a longer burning duration. This can lead to reduced engine power, decreased thermodynamic efficiency, and an excess of unburned ammonia in the exhaust. When used in compression-ignition engines, ammonia fuel requires pilot ignition of a diesel-like fuel (or another fuel with a relatively lower autoignition temperature than ammonia) to ignite and burn the ammonia fuel. Autoigniting pure ammonia requires a significantly higher compression ratio than those currently used in modern diesel engines. In addition, liquid ammonia also has a much higher latent heat of vaporization. In both existing spark-ignition engines and existing compression-ignition configurations, a considerable amount of unburned ammonia can be expected in the exhaust, even when ammonia fuel is mixed with another form of fuel to facilitate flammability.

[0008] In response to these shortcomings of ammonia-fueled internal combustion engines, and to improve combustion performance compared to conventional spark-ignition combustion, pre-combustion chambers (also known as sub-chambers) have been developed, particularly in large-bore gas engines where the drawbacks associated with low flame velocity are exacerbated by the large cylinder volume.

[0009] The subchamber is typically provided as a smaller chamber that is in fluid communication with the main chamber, thereby configuring it for initial combustion to facilitate the combustion of fuel in the main chamber. The pre-combustion occurring in the subchamber acts as a much stronger ignition source for the main chamber than, for example, could be achieved through a spark ignition system in a conventional gasoline engine.

[0010] A promising solution for more efficient combustion of ammonia fuel in internal combustion engines is to use hydrogen as an ignition enhancer. Hydrogen has superior combustion properties compared to conventional hydrocarbon fuels such as gasoline, including a much higher flame velocity and a much wider flammability limit. Recent studies have shown that ammonia-hydrogen mixtures can improve combustion speed compared to pure ammonia.

[0011] Continued development in this field is desirable. Specifically, this involves improvements in combustion efficiency, cost-effectiveness, and / or ease of manufacture / operation. [Overview of the Initiative]

[0012] According to one aspect of this disclosure, an ammonia-fueled internal combustion engine system, associated apparatus, methods, and control systems are provided. Some of the examples described offer improvements in one or more of the following: combustion efficiency, cost-effectiveness, and / or ease of manufacture / operation.

[0013] In one example, a system is provided comprising a decomposition device connectable to an ammonia fuel source. The decomposition device may be configured to produce a decomposed fuel containing a mixture of nitrogen and hydrogen by decomposing ammonia fuel supplied by the ammonia fuel source during engine operation. The system may comprise a main combustion chamber and an intake port and an exhaust port, respectively, which are in fluid communication with the main combustion chamber.

[0014] This system may include a secondary combustion chamber that is in fluid communication with the main combustion chamber via at least one orifice. The secondary combustion chamber may further include a decomposed fuel inlet to allow the introduction of decomposed fuel supplied from a decomposition device into the secondary combustion chamber.

[0015] This system may include an ignition device that is operably positioned with the sub-combustion chamber and configured to ignite the decomposed fuel in the sub-combustion chamber. The sub-combustion chamber and / or orifice may be configured to generate a stream of combustion fluid from the sub-combustion chamber to the main combustion chamber via the orifice when the decomposed fuel is ignited in the sub-combustion chamber, for example, to enable ignition of fuel present in the main combustion chamber.

[0016] This system may include a sensor arrangement configured to measure the properties of the decomposed fuel. The sensor arrangement may be configured to measure the properties of the decomposed fuel directly and / or indirectly.

[0017] This system may include a sensor arrangement and an electronic control device that communicates with the ignition device. The electronic control device may be configured to evaluate the characteristics of hydrogen present in the decomposed fuel using measurements received from the sensor arrangement. The control device may be configured to control the introduction of the decomposed fuel into the sub-combustion chamber according to the evaluated characteristics of the hydrogen.

[0018] An internal combustion engine system having the above configuration can be advantageously configured to control fuel introduction based on the characteristics of hydrogen in the decomposed fuel. Thus, the electronic control device may be provided with feedback regarding the characteristics of the decomposed fuel, specifically the characteristics of hydrogen present in the decomposed fuel.

[0019] An internal combustion engine system may also include a cracking device to advantageously provide "in situ" hydrogen production from ammonia-based fuels. The cracking device may also be known as a chemical cracking device, which breaks down ammonia into hydrogen and nitrogen. The cracking device may be configured to supply some or all of the hydrogen present in the pre-combustion fuel source. Depending on the efficiency of the cracking device, the pre-combustion fuel mixture may also contain undecomposed ammonia. Therefore, the output mixture of the cracking device may be a mixture of ammonia, hydrogen, and nitrogen (which may be considered, for example, partially decomposed).

[0020] The decomposition device may be a catalytic decomposition device. For example, the decomposition device may include a suitable catalyst that induces chemical decomposition upon contact with an ammonia source. Alternatively, the decomposition device may be a non-catalytic decomposition device, for example, comprising a device for thermal ammonia chemical decomposition.

[0021] Decomposed fuel can be used exclusively as a fuel source. For example, both the pre-combustion chamber and the main combustion chamber can be fueled with decomposed fuel. Alternatively, hydrogen-containing decomposed fuel can be used as a highly reactive pre-combustion fuel to facilitate the combustion of less reactive fuels in the main combustion chamber. For example, decomposed fuel can be used to facilitate the combustion of ammonia fuel present in the main combustion chamber. Therefore, it should be understood that the term “ammonia fuel engine” encompasses engines that are fueled directly by ammonia introduced into the main combustion chamber, as well as engines that are fueled by an ammonia fuel source that is decomposed into component compounds (e.g., completely or partially decomposed) before being introduced into the engine.

[0022] It will be understood that the engine may include typical components and features present in known internal combustion engines. The engine of this disclosure may be a two-stroke engine. The engine of this disclosure may be a four-stroke engine. The engine system may be a reciprocating engine and may include a piston in the cylinder. The intake and exhaust ports may typically be in fluid communication with the main combustion chamber. The engine system may include a rotary engine, such as a Wankel rotary engine, in which case it may include a housing and rotor.

[0023] An intake port may be equipped with an intake valve. An intake port may be an intake port or may be equipped with multiple ports. One or more intake ports may be equipped with one or more intake valves. An exhaust port may be equipped with an exhaust valve or may be equipped with multiple exhaust valves. An exhaust port may be an exhaust port or may be equipped with multiple ports. A cylinder intake port may be an air-only intake port. This may occur in configurations where fuel is not supplied to the inlet manifold, for example, when fuel is supplied to the main combustion chamber through a sub-combustion chamber, or when fuel is supplied to the main combustion chamber via "direct injection". In alternative configurations, the intake port may provide an air-fuel mixture to the main combustion chamber.

[0024] The evaluated characteristics of hydrogen present in the decomposed fuel may include the hydrogen concentration and, for example, the percentage of hydrogen in the total amount of hydrogen and ammonia present in the decomposed gas. The evaluated characteristics may also include the pressure and temperature of the decomposed fuel. It will be understood that the measured pressure or temperature of the decomposed fuel is also a measure of the hydrogen pressure and temperature in the decomposed fuel.

[0025] The sensor arrangement may be configured to measure the properties of the decomposed fuel. This may be carried out via direct measurement of the decomposed fuel. For example, the sensor arrangement may be in contact with or in proximity to the decomposed fuel. The sensor arrangement may be located in the flow path of the decomposed fuel. In a particular example, the sensor arrangement may be configured to perform direct measurements of the pressure and temperature of the decomposed fuel. It will be understood that these measurements correspond to measurements of the hydrogen pressure or temperature in the decomposed fuel.

[0026] The sensor arrangement may additionally or alternatively be configured to indirectly measure the properties of the decomposed fuel. For example, the sensor arrangement may be configured to measure properties obtained indirectly with respect to the decomposed fuel (e.g., in addition to, or instead of, directly measuring the fuel). For example, in some cases, the sensor arrangement may not be able to directly measure the decomposed fuel, but may be configured to measure a proxy or secondary indicator of the properties of the decomposed fuel. For example, the sensor arrangement may be configured to measure the properties of the decomposition device, where the properties of the decomposed fuel can be measured (e.g., determined or otherwise inferred). The sensor arrangement may be configured to measure the properties of the exhaust gas, where the properties of the decomposed fuel can be measured (e.g., determined or otherwise inferred). It will be understood that the sensor arrangement may enable the evaluation of the properties of the decomposed fuel by an electronic control device and is thus configured to measure the properties of the decomposed fuel.

[0027] The sensor arrangement may be configured to measure the properties of the decomposed fuel via direct and indirect measurements of the decomposed fuel (e.g., using measurements of the decomposition device to determine the properties of the decomposed fuel, together with directly measuring the fuel).

[0028] An electronic control device according to the present disclosure can be configured to perform an evaluation of the hydrogen characteristics in the decomposed fuel, for example, a direct evaluation. For example, the sensor arrangement can be associated with the decomposed fuel as long as measurements of the fuel characteristics are made. These measurements can be communicated to an electronic control device that can evaluate the characteristics of the decomposed fuel based on the direct fuel measurements measured by the sensor arrangement. In a particular example, the sensor arrangement can include a pressure and / or temperature sensor. The pressure and / or temperature information can be communicated to an electronic control device that can then (e.g., directly) evaluate the pressure and temperature characteristics. The hydrogen concentration and / or other components of the decomposed gas can be determined based on the pressure / temperature measurements according to a predetermined decomposition equilibrium relationship. The sensor arrangement can include a single sensor. The sensor arrangement can include a plurality of sensors.

[0029] In an example of indirect evaluation, an electronic control device can be configured to infer the characteristics of the decomposed fuel based on a secondary indicator of the fuel characteristics measured by the sensor arrangement. For example, the sensor arrangement can provide measurements of the engine exhaust to the electronic control device, and then the electronic control device can evaluate characteristics such as the hydrogen characteristics in the decomposed fuel. The sensor arrangement can provide information about the decomposition device to the electronic control device. For example, the sensor arrangement can include a temperature sensor configured to measure the temperature of the decomposition device. The electronic control unit device can be configured to use the decomposition device temperature measurement received from the decomposition device temperature sensor to evaluate the characteristics of specific components such as hydrogen present in the decomposed fuel. The electronic control device can receive the temperature information of the decomposition device and compare this with a predetermined decomposed fuel characteristic as a function of temperature. Such a predetermined decomposed fuel characteristic can be stored by the electronic control device, can be downloadable to the electronic control device, or can otherwise be available to the electronic control device.

[0030] In typical applications, the hydrogen concentration may primarily be a function of the decomposition temperature of a given decomposition apparatus device design. In embodiments of the present disclosure, an electronically controlled device may be provided with (e.g., stored) a predetermined map of temperature versus hydrogen concentration (i.e., hydrogen %) in the output of the decomposed gas. Such a map may be used by the electronically controlled device to evaluate the hydrogen concentration as a function of real-time temperature measurements of the decomposition apparatus device.

[0031] In one embodiment, an electronically controlled device may evaluate the hydrogen concentration in the decomposed fuel based on real-time temperature measurements, which are compared, for example, as a function of temperature, to a predetermined value of the hydrogen concentration in the decomposed fuel for a particular decomposition device. In a particular embodiment, the expression of the hydrogen concentration in the decomposed fuel may be measured indirectly from measurements of other components, e.g., ammonia and / or nitrogen, and then calculated. This may be achieved (with acceptable precision) from the following equilibrium chemical decomposition reaction: 2NH3 → N2 + 3H2.

[0032] Various measuring devices, such as ceramic ammonia sensors currently used to measure unreacted ammonia in the exhaust gas of engines equipped with selective catalytic reduction of nitrogen oxides, are available for the relevant gases. An exemplary instrument is the ECM NOx / NH3 5240 analyzer. In certain embodiments, the engine system of this disclosure may be equipped with several detectors or sensors having overlapping measuring ranges. This may provide the required level or fine control, which is particularly desirable at higher engine speeds.

[0033] The sensor arrangement may be configured to provide a real-time display of the decomposed fuel characteristics, which may allow an electronically controlled device to optimize the introduction of fuel into the sub-combustion chamber. In certain embodiments, a decomposed fuel supply source upstream of the decomposed fuel inlet may include one or more of a hydrogen concentration sensor, a pressure sensor, and a temperature sensor.

[0034] In certain embodiments of this disclosure, sensor arrangements and electronic control devices may be configured to evaluate the hydrogen concentration in the decomposed fuel. It will be understood that the performance of the decomposition device may not typically produce a consistent mixture of decomposed fuel during operation. The hydrogen concentration in the pre-combustion fuel source may be dispersed. The composition of the decomposed fuel may change, in particular, as a function of the temperature of the decomposition device. Thus, the amount of hydrogen present in the decomposed fuel may change. It will be understood that continuous evaluation of the hydrogen concentration may favorably enable the electronic control device to control fuel delivery according to the amount of hydrogen present in a given amount of decomposed fuel at a given time.

[0035] As described above, the hydrogen concentration can be evaluated through measurements of the decomposed fuel, for example, direct measurements. Hydrogen concentration measurements can be performed using electrical conductivity sensors. Hydrogen concentration measurements can be performed using electrochemical sensors. Evaluation of hydrogen concentration can be advantageously communicated to electronic control devices regarding the ratio of hydrogen-containing pre-combustion fuel to a less reactive main fuel (e.g., ammonia). In certain embodiments, the sensor arrangement is configured to measure the pressure and temperature of the decomposed fuel.

[0036] In certain embodiments, an electronically controlled device is configured to control the duration and timing of the introduction of the decomposed fuel into the pre-combustion chamber. Control of duration and timing may be via communication between the electronically controlled device and the decomposed fuel inlet. The decomposed fuel inlet may include a decomposed fuel injector that communicates with the electronically controlled device. This communication may be electronic. The decomposed fuel injector may be configured to inject a spray of decomposed fuel into the pre-combustion chamber. The decomposed fuel injector may be positioned in the pre-combustion chamber. The decomposed fuel injector may be configured for direct injection of the decomposed fuel into the pre-combustion chamber. The decomposed fuel injector may be configured to indirectly inject the decomposed fuel into the pre-combustion chamber. For example, the decomposed fuel injector may be located upstream of a fuel conduit leading to the pre-combustion chamber.

[0037] The characteristics of the hydrogen from the decomposed fuel can be used by an electronically controlled device to determine preferred injection parameters such as injection duration and timing. Injection timing can be set to occur at specific points in the engine cycle. In an internal combustion engine involving a piston, the engine cycle may relate to the position and direction of motion of the piston within the cylinder. In a rotary engine, the engine cycle may relate to the angular position of the rotor within the engine housing. Injection timing can also be controlled by an electronically controlled device and may be set to occur at specific times relative to the operation of the ignition device.

[0038] In certain embodiments, the electronic control device is configured to control the amount (e.g., mass) of hydrogen introduced into the sub-combustion chamber. The electronic control device may be configured to control the amount of hydrogen present in the sub-combustion chamber by controlling the amount of decomposed fuel introduced into the sub-combustion chamber. In certain examples, the electronic control device may adjust the injection timing to introduce a specific amount of decomposed fuel into the sub-combustion chamber in order to introduce a specific amount of hydrogen into the sub-combustion chamber. In this case, a higher hydrogen concentration in the decomposed fuel may correspond to a shorter injection duration, and vice versa.

[0039] In another example, the electronic control device may be configured to adjust the composition of the decomposed fuel introduced into the sub-combustion chamber. The electronic control device may be configured to control the operation of the decomposition device in order to adjust the concentration of hydrogen present in the decomposed fuel. The electronic control device may be configured to control the operation of the decomposition device. The electronic control device may be configured to affect the performance of the decomposition device. For example, the engine may further include a controllable heating device configured to heat the decomposition device, and the heating device communicates with the electronic control device. The communication may be electronic communication. Thus, the electronic control device may selectively heat the decomposition device if it is desirable to improve the performance of the decomposition device, for example, to increase the concentration of hydrogen present in the decomposed fuel. In certain embodiments, the electronic control device may control the operation of the decomposition device according to a target hydrogen concentration of 5% to 35% by volume in the decomposed fuel (for example, during normal operation of the engine system).

[0040] Hydrogen concentration refers to the portion of hydrogen in the total amount of combustible fuel, including the sum of hydrogen and ammonia. Therefore, hydrogen concentration can be defined according to the following formula:

number

[0041] It should be understood that hydrogen concentration refers to the proportion of a hydrogen-ammonia mixture that is composed of hydrogen, not the ratio of hydrogen to ammonia. This convention is used because hydrogen and ammonia are combustible fuels present in the decomposed fuel, and the presence of non-combustible gases such as nitrogen during engine ignition is ignored. Therefore, the target hydrogen fuel concentration refers to the percentage of combustible fuel composed of hydrogen.

[0042] As mentioned above, ammonia chemiolysis can occur according to the following reaction: 2NH3 → N2 + 3H2. It will be understood that the portion of the total amount of hydrogen in the fuel (H2 + NH3) will vary depending on the efficiency at which ammonia chemiolysis occurs. As stated, certain embodiments may control the performance of the decomposition device to achieve a target hydrogen concentration of 5–35% in the combustible fuel. This may be particularly advantageous when a single fuel injector is used to introduce the decomposed fuel into both the pre- and main combustion chambers. In this case, there is no separate ammonia fuel injector capable of diluting the hydrogen concentration to the target range, and therefore the decomposition device can be controlled to partially decompose the mixture to achieve the target range in the cylinder, as well as the delivery and ignition of the mixture, without the mixture undergoing a change in composition. In other words, the operation of the decomposition device may be provided so that only a specific amount, and not all, of ammonia is decomposed. This may conceptually be called the “efficiency” of the decomposition device, but efficiency may be considered to be in relation to the amount or percentage of decomposition relative to complete decomposition being performed (e.g., relative to 100%), rather than any power efficiency of the decomposition device.

[0043] In some embodiments, a 5% hydrogen concentration may result from the decomposition of approximately 4% ammonia. In this case, the ammonia can be chemically decomposed into a decomposed fuel containing 93% ammonia, 5% hydrogen, and 2% nitrogen. In this example, the percentage of hydrogen is 5 / (5+93) = approximately 5.1%.

[0044] In some embodiments, a hydrogen concentration of 35% may be due to the decomposition of approximately 26% ammonia. In this case, the ammonia can be chemically decomposed into a decomposed fuel containing 59% ammonia, 31% hydrogen, and 10% nitrogen. In this example, the percentage of hydrogen is 31 / (31+59) = approximately 34.4%.

[0045] The efficiency of the decomposition device may be controllable through the adjustment of the temperature of the decomposition device. The temperature of the decomposition device can be controlled in various ways, for example, by adjusting the amount of waste heat that can be exchanged with the decomposition device. For example, the amount of waste heat that can be exchanged with the decomposition device can be controlled to maintain the decomposition efficiency within a target range. When the decomposition efficiency approaches the upper limit of the target range, or If the threshold is exceeded, a portion of the exhaust gas may be selectively bypassed from the decomposition device to limit or reduce the decomposition efficiency, or it may be otherwise regulated by a throttle. Another means of controlling the temperature may be a controllable heating device associated with the decomposition device. The heating device may operate in cooperation with heating from the exhaust gas.

[0046] As stated, the target range may be selected to achieve the target hydrogen concentration. The target hydrogen concentration may be in the range of 5% to 35% during normal engine system operation, but may be higher during cold starts or in very cold ambient conditions.

[0047] In certain embodiments, ammonia fuel can be introduced into the main combustion chamber using a separate ammonia fuel injector. In this case, the decomposition device can operate with a decomposition efficiency of over 26% and produce a hydrogen concentration of over 35%. During fuel injection, the hydrogen fuel concentration in the decomposed fuel can be diluted by the introduction of ammonia fuel from the ammonia fuel injector to achieve a hydrogen concentration of 5-35% in the cylinder.

[0048] In cases where the decomposition efficiency is controlled to intentionally produce a decomposed fuel containing hydrogen and ammonia (e.g., hydrogen concentration within 5-35%), it will be understood that the decomposed fuel produced by the decomposition device is partially decomposed, insofar as it contains undecomposed ammonia, hydrogen, and nitrogen. In other cases where the ammonia fuel is injected separately from the decomposed fuel, the decomposition efficiency does not need to be adjusted with the throttle and can reach 100%. In this case, the decomposed fuel is completely decomposed and contains substantially only hydrogen and nitrogen.

[0049] It should be noted that control of the disassembly device by an electronically controlled device can occur directly or indirectly. In one example of direct control, the electronically controlled device may be configured to directly transmit command communications to a controllable heating device. In one example of indirect control, the electronically controlled device may transmit command communications to an intermediate control device associated with the heating device. In either case, it will be understood that the electronically controlled device can control the operation of the heating device, and consequently, the operation of the disassembly device.

[0050] In certain embodiments, the electronic control device can increase the duration of hydrogen introduction of the decomposed fuel to introduce the amount of hydrogen required to meet the engine's determined power requirements. This can be achieved by a predetermined value as a function of the decomposition efficiency, based on the operating temperature of the decomposition device where ammonia decomposition occurs. The electronic control device can also be programmed to accept the percentage of hydrogen in the fuel mixture as input. In addition, the control device can also be configured to operate in a closed-loop system by receiving feedback from a sensor arrangement that measures the percentage of hydrogen in the gas mixture output from a fuel source such as an ammonia decomposition device, and thus the injector can be actuated to inject the required amount of hydrogen depending on the engine load and speed.

[0051] In some embodiments, the fuel present in the main combustion chamber may be decomposed fuel, which is produced by a decomposition device and introduced into the main combustion chamber via a sub-combustion chamber, for example, through an orifice in the sub-combustion chamber. This configuration can advantageously allow both chambers to be fueled from a single decomposed fuel inlet. In certain embodiments, fuel supply to the main combustion chamber via the sub-combustion chamber can be achieved by providing a decomposed fuel inlet with a sufficiently high flow capacity. This can advantageously avoid the need for a separate fuel inlet to deliver fuel to the main combustion chamber. Fueling the main combustion chamber via the sub-combustion chamber can avoid the need for a separate fuel injector located at the engine intake port (port injection) or cylinder head (direct injection). This configuration can be particularly advantageous for two-stroke engines where there is a risk of fuel slip during exhaust scavenging. Specifically, fuel slip can be mitigated or avoided by initiating injection after the exhaust valve is closed. Furthermore, such an arrangement can allow for ease of modification.

[0052] As already mentioned, the inlet for the decomposed fuel may be a decomposed fuel injector that communicates with and is controllable by an electronically controlled device. The communication may be electronic. In certain embodiments, the electronically controlled device is configured to control the introduction of the decomposed fuel into the main combustion chamber by controlling the timing and duration of the introduction of the decomposed fuel into the pre-combustion chamber during operation. For example, the electronically controlled device may set the injection duration to provide a volume of decomposed fuel that is high enough to fuel both the pre-combustion chamber and the main combustion chamber. The electronically controlled device may set the injection timing to coincide with the intake and / or compression strokes, thereby causing the fuel flow from the pre-combustion chamber to the main combustion chamber through the orifice as a result of the pressure difference resulting from the injection event.

[0053] The decomposed fuel inlet may be configured to deliver the decomposed fuel to the sub-combustion chamber at a flow rate that enables fuel supply to the main combustion chamber with the decomposed fuel flowing from the sub-combustion chamber through an orifice to the main combustion chamber. The fuel inlet may be configured to introduce the fuel flow into the sub-combustion chamber in the direction of flow toward the main combustion chamber. The fuel inlet of the sub-combustion chamber may be oriented toward an orifice through which there is fluid communication between the chambers.

[0054] In certain embodiments of this disclosure, the fuel present in the main combustion chamber includes ammonia fuel. In the embodiments, the engine system includes an ammonia fuel inlet configured to introduce ammonia fuel into the main combustion chamber, and the ammonia fuel present in the main combustion chamber includes ammonia fuel supplied by the ammonia fuel inlet. The ammonia fuel inlet may be supplied with ammonia fuel by the same ammonia fuel source that supplies ammonia fuel to the cracking device. This configuration is advantageous because it allows two fuel types (i.e., cracked fuel and uncracked ammonia fuel) to be supplied by a single fuel source and, for example, from a single ammonia fuel tank. This may be advantageous in terms of volume constraints, insofar as a single fuel reservoir is required instead of multiple fuel reservoirs. Alternatively, the main combustion chamber and the cracking device may be supplied with ammonia fuel from two or more different ammonia fuel sources.

[0055] The ammonia fuel inlet can be provided through several different configurations. In one example, the ammonia fuel inlet may be configured to introduce ammonia fuel into the main combustion chamber via a sub-combustion chamber and an orifice. An ammonia fuel inlet configured to introduce ammonia fuel through a sub-combustion chamber may share a similar configuration to the example discussed above, in which the decomposed fuel inlet is configured to introduce decomposed fuel into the main combustion chamber via a sub-combustion chamber. For example, the ammonia fuel inlet may be configured to facilitate the introduction of ammonia fuel into the main combustion chamber by promoting the ammonia fuel flow path toward the orifice. The ammonia fuel inlet may be configured to deliver a flow rate or total volume of ammonia fuel to a sub-combustion chamber configured to supply fuel to the main combustion chamber.

[0056] In certain examples, the ammonia fuel inlet is located in a sub-combustion chamber. Thus, the sub-combustion chamber may include both a decomposed fuel inlet and an ammonia fuel inlet. Therefore, the sub-combustion chamber can be described as a multi-inlet sub-combustion chamber. One or both of the decomposed fuel inlet and the ammonia fuel inlet may be equipped with an electronic fuel injector. In some embodiments, the main fuel inlet and the ammonia fuel inlet are located adjacent to each other in the sub-combustion chamber.

[0057] Providing a "multiple-inlet" sub-combustion chamber allows both decomposed fuel and ammonia fuel to be introduced through the sub-combustion chamber, and thus can be particularly advantageous in applications where cylinder space (or, in the case of a rotary engine, housing space) is limited, insofar as it avoids the need for a separate ammonia fuel inlet located elsewhere in the cylinder or housing. If the engine system is undergoing conversion to include a sub-combustion chamber, a multiple-inlet sub-combustion chamber may allow the sub-combustion chamber to be installed in the location where the original fuel intake was located, and may allow two fuel types to be provided to an engine system originally designed for a single fuel type.

[0058] In an alternative example, the ammonia fuel inlet may be configured to introduce ammonia fuel into the main combustion chamber via the intake port of the engine system. The ammonia fuel inlet may be located at the intake port (e.g., intake port) of the cylinder or rotary engine housing. The ammonia fuel inlet may be located upstream of the intake port. For example, the ammonia fuel inlet may be configured to deliver ammonia fuel to an inlet manifold that supplies an air-fuel mixture to one or more cylinders.

[0059] In certain embodiments, the decomposed fuel inlet or the supply line leading to the decomposed fuel inlet may be equipped with a backflow prevention check valve. In certain embodiments, the ammonia fuel inlet or the supply line leading to the ammonia fuel inlet may be equipped with a backflow prevention check valve. In another embodiment, the ammonia fuel inlet is configured for direct injection of ammonia fuel into the main combustion chamber. For example, the ammonia fuel inlet may communicate directly with the main combustion chamber. The ammonia fuel inlet may be equipped with an ammonia fuel injector having an outlet positioned in the cylinder head or the wall of the main combustion chamber.

[0060] In certain embodiments, the operation of the decomposed fuel inlet and / or ammonia fuel inlet may be independent of the electronically controlled device. For example, the decomposed fuel inlet and ammonia fuel inlet may be mechanically controlled according to the engine cycle. The engine may have a valve and camshaft arrangement, thereby introducing the decomposed fuel inlet and ammonia fuel inlet via valves mechanically actuated by the camshaft or other timing arrangement. In this example, the electronically controlled device does not necessarily have to control the introduction of fuel into the pre-combustion chamber, but may control the operation of the decomposition device according to the evaluated hydrogen characteristics. For example, by controlling a heating device associated with the decomposition device to adjust the performance of the decomposition device.

[0061] Alternatively, the ammonia fuel inlet may be equipped with an ammonia fuel injector that communicates with and is controlled by an electronic control device. This configuration advantageously allows the introduction of ammonia fuel to be controlled by the electronic control device and as a function of the hydrogen characteristics evaluated by the electronic control device.

[0062] In certain embodiments, the electronic control device is configured to control the duration and timing of the introduction of ammonia fuel into the pre-combustion chamber by controlling the operation of the ammonia fuel injector. In configurations where ammonia fuel is supplied to the main combustion chamber via the pre-combustion chamber, the electronic control device may be configured to control the introduction of ammonia into the main combustion chamber by controlling the duration and timing of the introduction of ammonia fuel into the pre-combustion chamber. In configurations where ammonia fuel is supplied to the main combustion chamber via the engine intake port or via direct injection, the electronic control device may be configured to control the introduction of ammonia fuel into the main combustion chamber by controlling the introduction of ammonia fuel to those respective locations.

[0063] In certain embodiments, the electronic control device is configured to determine the volume of ammonia introduced into the main combustion chamber according to an assessment by the electronic control device of the amount of hydrogen present in the decomposed fuel. This may, advantageously, allow combustion performance to be improved or optimized according to the amount of hydrogen available for combustion via the introduction of the decomposed fuel.

[0064] This disclosure allows for advantageous control of the amount of hydrogen supplied to the sub-combustion chamber by first evaluating the amount of hydrogen available in the decomposed fuel source. For example, the ratio of the decomposed fuel introduced into the sub-combustion chamber to the ammonia fuel introduced into the main combustion chamber can be adjusted to achieve a desired ratio of hydrogen to ammonia.

[0065] Those skilled in the art will understand that the preferred amount of hydrogen present in the sub-combustion chamber depends on a wide variety of factors, including the volumes of the main and sub-combustion chambers, engine speed requirements, engine load, engine temperature, and ammonia slip present in the exhaust gas (i.e., unburned ammonia).

[0066] The preferred hydrogen-to-ammonia ratio can vary considerably depending on specific engine and operating parameters. This disclosure provides general application principles that those skilled in the art can use to generate the above-mentioned favorable feedback loop between the evaluated hydrogen characteristics in the decomposed fuel and the introduction of the decomposed fuel into the sub-combustion chamber or control of the decomposition device. The optimal timing and duration of sub-combustion chamber injection, the timing and duration of main chamber injection (in embodiments with a main chamber injector), and the ignition timing can vary depending on the application.

[0067] In certain embodiments, an electronically controlled device monitors the characteristics of hydrogen in the decomposed fuel source to assess whether one or more characteristics are within or outside a favorable range. In one example, the electronically controlled device may detect or infer a decrease in the concentration of hydrogen present in the decomposed fuel source. Accordingly, the electronically controlled device may assess whether the decrease causes the ratio of hydrogen in the sub-combustion chamber to ammonia in the main combustion chamber to fall below a favorable range (which may depend on various engine parameters, including temperature, engine load, and speed requirements). If so, the electronically controlled device may increase the injection duration of the decomposed fuel into the sub-chamber while decreasing the amount of ammonia fuel introduced into the main chamber, or it may control the decomposition device to increase the hydrogen concentration, or both, in order to return this ratio to the favorable range in order to meet the engine load and speed requirements.

[0068] In certain embodiments, the electronic control device is configured to control the introduction of ammonia fuel into the main combustion chamber and the introduction of decomposed fuel into the secondary combustion chamber according to a target hydrogen concentration. In certain embodiments, the target hydrogen concentration of the total amount of hydrogen relative to the total amount of combustible fuel introduced in the engine cycle is 5% to 35% by volume. As discussed above, the total amount of combustible fuel can be defined according to the following formula:

number

[0069] In other words, the hydrogen concentration is the portion of hydrogen fuel and ammonia fuel composed of hydrogen, ignoring other gases that are not typically burned during normal engine operation.

[0070] In this embodiment, the electronic control device may attempt to achieve or maintain a hydrogen concentration of 5% to 35%. This range can favorably provide enough hydrogen to ignite the ammonia fuel in the main combustion chamber without providing an excess of hydrogen that could cause engine damage or overheating, and can typically waste no more hydrogen than the ammonia supply.

[0071] Under certain operating conditions, the target hydrogen concentration may be higher than 35%. For example, during cold starts and / or in extremely low ambient temperature conditions, the engine system may intentionally target a higher hydrogen fuel concentration for faster warm-up. Once the engine system reaches its typical operating temperature, it may then maintain the target hydrogen concentration (e.g., 5–35%).

[0072] The electronic control device may be configured to achieve a hydrogen-to-ammonia concentration within a target range by adjusting the injection duration of the pre-chamber fuel injector and the main-chamber fuel injector according to the characteristics of hydrogen evaluated by the electronic control unit and sensor arrangement. In certain embodiments of the present disclosure, the electronic control device determines the volume of ammonia to be introduced into the main combustion chamber as a function of the volume of hydrogen available for introduction into the pre-combustion chamber.

[0073] In certain embodiments, the decomposed fuel inlet is equipped with a decomposed fuel injector that communicates with and is controlled by an electronically controlled device, and for each engine cycle, the electronically controlled device is responsible for the following sequence of actions: i. Determine the engine operation request. ii. To evaluate the pressure and temperature of hydrogen in the decomposed fuel produced by the decomposition device via the sensor arrangement. iii. Setting the timing and duration of the disassembled fuel injector. iv. Setting the timing and duration of the ammonia fuel injector, v. Set the ignition timing of the ignition device.

[0074] According to the embodiment, the engine operation request is an engine load request and / or an engine speed request. According to the embodiment, steps iii. and iv. above are set according to the determination in steps i. and ii. That is, the timing and duration of the main fuel injector and pre-combustion fuel injector are set according to the engine load and speed request (received, for example, from a sensor associated with the accelerator pedal of the vehicle) and according to the indication of hydrogen characteristics in the pre-combustion fuel supply source upstream of the pre-combustion fuel injector, received from the sensor arrangement.

[0075] In certain embodiments, the decomposed fuel produced by the decomposition device is supplied to the decomposed fuel inlet without undergoing a separation process. In this regard, the gas mixture output by the decomposition device may be the same compositional mixture delivered to the decomposed fuel inlet and introduced into the pre-combustion chamber. This offers advantages over systems in which hydrogen is filtered or separated from the pre-combustion fuel mixture. The engine according to this disclosure advantageously does not necessarily require a separation process performed upstream of the decomposed fuel injector. This can reduce the complexity, weight, and cost of the engine.

[0076] Furthermore, the internal combustion engine system according to this disclosure may not require a buffer tank between the disintegration device and the pre-combustion chamber. For example, the output of the disintegration device may be supplied directly to the pre-combustion chamber via the pre-combustion fuel line, without an intermediate storage tank between the disintegration device and the pre-combustion fuel inlet. Omitting the separation system and / or buffer tank may favorably reduce the complexity, weight, and cost of the system.

[0077] The internal combustion engine system according to this disclosure can be significantly simplified compared to existing systems in that it can directly supply a mixture of unseparated decomposed fuel, including hydrogen and non-hydrogen gases, to a pre-combustion chamber. The decomposition device may be configured to partially decompose ammonia, thereby the hydrogen concentration in the decomposed gas output from the decomposition device is in the range of 5% to 35% by volume.

[0078] The engine system can be advantageously configured to operate without further significantly complicating the system by eliminating the need to isolate hydrogen from nitrogen present in the decomposed gas. This advantage is provided via an electronically controlled device configured to use measurements received from a sensor arrangement to evaluate the characteristics of hydrogen present in the decomposed fuel and to control the introduction of the decomposed fuel into the sub-combustion chamber according to those evaluated hydrogen characteristics.

[0079] A further advantage associated with operating using partially decomposed ammonia containing 5% to 35% hydrogen is that this engine system can operate with smaller or less expensive decomposition devices compared to engine systems that relied on complete ammonia decomposition.

[0080] A further advantage associated with operating using partially decomposed ammonia containing a hydrogen concentration of 5% to 35% by volume is that such engine systems result in higher overall efficiency compared to more or completely decomposed ammonia. This is typically due to lower energy requirements involved in the decomposition process, consisting of energy to heat the ammonia to its decomposition temperature, energy losses involved in the decomposition process, and energy to cool the decomposed gas to a lower temperature suitable for injection.

[0081] A further advantage associated with operating with partially decomposed ammonia containing 5% to 35% hydrogen by volume is that the decomposed gas output from the decomposition device and used as pre-combustion fuel may require less cooling before injection, or in some cases, may need to be cooled together with the gas compared to scenarios where higher or complete decomposition is used. This may be due to the fact that higher hydrogen concentrations may result in reduced resistance to abnormal combustion events, such as pre-ignition and knocking, when used without cooling.

[0082] A further advantage associated with operating using partially decomposed ammonia containing hydrogen concentrations of 5% to 35% by volume is that the engine system can be configured to operate without separating hydrogen from nitrogen present in the decomposed gas. Higher or complete decomposition of ammonia results in higher nitrogen concentrations, which can affect engine performance if not separated. Nitrogen acts as a diluent, which can reduce the combustion rate and, consequently, reduce engine efficiency. In addition, NOx (nitrogen oxides) and N2O emissions may be higher. Therefore, nitrogen separation from the decomposed gas may be required, which would further significantly complicate the system.

[0083] It will be understood that the ignition and combustion of a hydrogen-containing decomposed fuel mixture will increase the pressure in the sub-combustion chamber above the pressure in the main combustion chamber. Ignition of the decomposed fuel in the sub-combustion chamber can create a stream of combustion fluid that is constricted and released into the main combustion chamber through at least one orifice connecting the sub-combustion chamber to the main combustion chamber.

[0084] The stream of combustion fluid generated by the ignition of the decomposed fuel may include a stream of combustion gases or combustion liquids, or mixtures thereof. The stream of combustion fluid may include a stream of combustion fuel. The stream of combustion fluid may include a flame jet. For example, a flame jet emerging from a sub-combustion chamber, which may contain combustion gases, radicals, and a mixture of combustion and unburned fuel. The stream of combustion fluid may help the fuel in the main chamber burn more quickly and completely. The stream of combustion fluid may include a flame jet with a flame front. For example, the stream of combustion fluid may include a flame front propagating through the stream of combustion fluid. The wake of the flame front may include the burned fluid or the fluid that is burning (or a mixture of these fluids). The fluid ahead of the flame front injected into the sub-combustion chamber may contain unburned fuel.

[0085] In certain embodiments of this disclosure, fluid communication between the sub-combustion chamber and the main combustion chamber is provided by a single orifice. In certain embodiments of this disclosure, multiple orifices are provided connecting the sub-combustion chamber to the main combustion chamber. The multiple orifices may include 2 to 10 orifices in certain examples. Certain embodiments may include 4 to 8 orifices. The multiple orifices may be configured to provide multiple combustion fluid streams to the main combustion chamber. This may generate multiple combustion fluid streams. Each of the multiple combustion fluid streams may be a highly turbulent jet of combustion fluid (e.g., a turbulent flame jet) that more rapidly ignites the fuel present in the main combustion chamber as a result of multiple dispersed ignition sites.

[0086] The disclosed method of burning a hydrogen-containing decomposed fuel in a sub-combustion chamber allows the same power output to be achieved with less hydrogen required (compared to burning a mixture of hydrogen and ammonia in the main combustion chamber in some earlier ammonia fuel engine designs). Accordingly, hydrogen consumption is reduced, which improves overall engine efficiency. In other words, for the same level of hydrogen fuel consumption rate, the use of a sub-combustion chamber is considered to provide higher power output at the same level of engine thermal efficiency, if not a higher level.

[0087] In certain embodiments, the sub-combustion chamber has a volume of at least 3% of the cylinder clearance volume. This can advantageously generate a flame jet with an enthalpy high enough to successfully burn ammonia in the main chamber. The clearance volume will be understood to be the volume of the main combustion chamber remaining when the piston is at top dead center (TDC), i.e., when it is closest to the cylinder head and furthest from the crankshaft.

[0088] According to embodiments of the present disclosure, the decomposition device is in thermal communication with waste heat generated by the engine. According to embodiments of the present disclosure, the decomposition device comprises an electric heating element. In certain embodiments, the decomposition device may be heated by engine waste heat in conjunction with the electric heating element. The electric heating unit can advantageously maintain sufficient decomposition performance and hydrogen production at low engine temperatures and, for example, for engine starting. The electric heating unit may communicate with and be controlled by an electronic control unit.

[0089] According to certain embodiments, the sub-combustion chamber includes a coating of a catalytic material configured to partially convert ammonia present in the sub-combustion chamber into hydrogen. The catalytic material may be coated on the inner wall of the sub-combustion chamber and / or on the surface of at least one orifice. The use of a catalytic material coating in the sub-combustion chamber may, in some cases, act to complement the hydrogen content in the sub-combustion chamber.

[0090] The ignition device in the pre-combustion chamber may be any suitable device known to those skilled in the art. The ignition device may include a laser ignition device. The ignition device may include a plasma ignition device. The spark plug may include a spark plug that communicates with an electronic control device. This communication may be electronic communication.

[0091] In certain embodiments, the engine further comprises a heating device configured to heat the air supplied through the engine intake. The heating device may further help to promote or facilitate optimized combustion by introducing hot air through the engine intake, thereby providing a heated air-fuel mixture.

[0092] Multiple sensors may include one or more pressure sensors, temperature sensors, or gas concentration sensors such as ammonia sensors, hydrogen sensors, or nitrogen sensors. Sensor packs may be positioned to measure the decomposed fuel output from a decomposition device. Sensor arrangements may be positioned in a fuel line connecting the output terminal of the decomposition device to the inlet of the decomposed fuel. Sensor arrangements may comprise packs of sensors located adjacent to each other. Sensor arrangements may comprise sensors located in different parts of the engine system and not adjacent to each other. Each sensor in a sensor arrangement may be configured to communicate with an electronic control device.

[0093] According to a particular embodiment of this disclosure, at least one orifice has a diameter of 0.8 mm to 3.0 mm. In a particular embodiment, the engine system includes a plurality of orifices, each of which has a diameter of 0.8 mm to 3.0 mm.

[0094] In certain forms of this disclosure, the engine system has a cylinder with a cylinder head, and the sub-combustion chamber is located on the cylinder head. It will be understood that the location of the sub-combustion chamber may vary depending on the engine design, cylinder geometry, and available space for locating the sub-combustion chamber. Therefore, it should be understood that the sub-combustion chamber may have alternative spatial positionings.

[0095] In certain forms of this disclosure, the engine includes a decomposed fuel buffer tank located upstream of the fuel inlet and configured to buffer the supply of decomposed fuel provided to the fuel inlet.

[0096] It will be understood that the engine systems according to this disclosure may typically comprise a plurality of cylinders. In embodiments of this disclosure, the engine comprises a plurality of cylinders, and each cylinder in the plurality of cylinders includes a main combustion chamber and a secondary combustion chamber.

[0097] According to embodiments of the present disclosure, the engine further comprises a compressor device configured to compress the decomposed fuel upstream of the sub-combustion chamber. In certain embodiments, the compressor device is configured to compress the decomposed fuel to a pressure not exceeding 100 bar. The compressor device may be controlled by an electronic control device. The compressor device can be used to increase the pressure of the decomposed gas output from the decomposition device to a pressure that allows desired injection parameters to be achieved. For example, in certain embodiments, the compressor device is configured to compress the decomposed fuel to a pressure that allows a choke flow across the decomposed fuel injector.

[0098] It will be understood that achieving choke flow in the nozzle of a pre-combustion fuel injector generates a fuel velocity close to the speed of sound in the throat (i.e., the narrowed portion of the nozzle), and that a region of supersonic flow can also be achieved immediately downstream of the throat. This is beneficial for generating a high level of turbulence in the pre-combustion chamber, and consequently, improves combustion efficiency. Furthermore, choke flow promotes a constant and stable mass flow rate across the injector nozzle, thus enabling better control of injection duration.

[0099] During choke flow, the hydrogen injection mass is related to pressure and temperature according to the following equation:

number

[0100] During the ceremony,

number

[0101] As this function shows, mass flow rate is related to both pressure and temperature. Specifically, mass flow rate is directly related to pressure and inversely proportional to the square root of temperature. Compared to supply from pressurized tanks such as hydrogen gas tanks, supply of decomposed fuel from decomposition devices can be more unstable in terms of pressure, temperature, and hydrogen concentration, typically due to changes in temperature, decomposition efficiency, etc. Therefore, measuring or evaluating at least some of these characteristics of decomposed fuel provides important advantages in the operation of engines fueled by "field" decomposed fuel supply. In particular, measuring pressure and temperature can enable the evaluation of mass flow rate, allowing electronic control devices to set preferred injection parameters.

[0102] The use of choke flow may allow for the evaluation of the injection mass flow rate into the sub-combustion chamber without requiring an evaluation of the pressure difference between the fuel pressure of the decomposed gas and the sub-combustion chamber pressure. This can advantageously reduce physical complexity as it does not require a sub-combustion chamber pressure sensor, and further reduces the computational load on the electronic control unit as the injection mass flow rate can be predicted without requiring a real-time data stream from the sub-combustion chamber pressure sensor to evaluate the pressure difference between the pre-combustion fuel and the sub-combustion chamber pressure.

[0103] The use of choke flow can, advantageously, allow for the use of a relatively low-pressure decomposed gas injection system, which can typically reduce cost and complexity. In certain embodiments of the engine system according to this disclosure, the timing of the injection of decomposed gas into the sub-combustion chamber is delayed as much as possible while maintaining choke flow during the injection period. This can, advantageously, allow for a higher concentration of decomposed gas in the sub-combustion chamber at ignition. In some cases, this can advantageously generate a stream of combustion fluid (e.g., a stream of combustion fluid that may include one or more flame jets) having a higher enthalpy of the main ammonia fuel in the main chamber and subsequent more rapid combustion. In alternative scenarios where the flow is not choke, controlling the injection mass during the injection period can be more complex, even when using a pre-combustion pressure sensor to assess the pressure difference.

[0104] It should be understood that controlling pre-combustion chamber injection to achieve choke flow can favorably increase the certainty of the mass flow rate associated with the injection. This is particularly advantageous when operating the engine system of this disclosure with a pre-combustion fuel containing partially decomposed ammonia fuel, specifically a decomposed gas containing 5 to 35 volume percent hydrogen. It will be understood that the precision required when injecting pre-combustion fuel with relatively low hydrogen concentrations can typically be increased to ensure sufficient hydrogen feed to the pre-combustion chamber. In contrast, injection precision may be less critical in alternative engine systems that typically use significantly higher concentrations of hydrogen as the pre-combustion fuel. However, as discussed above, such systems have the disadvantages of requiring larger or more efficient (and more expensive) decomposition devices, and / or requiring separation systems to increase hydrogen concentration, and / or the complexity, cost, and weight associated with hydrogen tanks and their respective components.

[0105] Therefore, embodiments of the present disclosure in which an electronically controlled device evaluates the pressure and temperature of the decomposed fuel can advantageously enable precise control of hydrogen injection through a choke flow state. Precise control then facilitates repeatable ignition of the sub-combustion chamber, which facilitates a consistent stream of combustion fluid entering the main combustion chamber from the sub-combustion chamber. A consistent combustion stream may involve less variation in flame enthalpy and flow pattern. This can facilitate repeatable combustion of ammonia fuel, helping to improve engine efficiency, emissions, and ease hydrogen requirements.

[0106] In certain embodiments, the electronic control device is configured to increase the injection duration of the decomposed fuel into the sub-combustion chamber to meet high power demand conditions or to inject the required amount of hydrogen during cold starting. This can be implemented using evaluated characteristics of the hydrogen present in the decomposed fuel source. The control device can also be programmed to accept a percentage of hydrogen in the fuel mixture as input. This can be used, for example, in embodiments where a consistent fuel mixture is used.

[0107] The disclosed internal combustion engines may include various types of internal combustion engines, and it will be understood that they include reciprocating engines, rotary engines, and the like. Reciprocating engines include, but are not limited to, traditional piston engines, crankless engines, opposed-piston engines, and free-piston engines.

[0108] Another aspect of the present disclosure provides a method for operating an ammonia-fueled internal combustion engine, which includes a sub-combustion chamber in fluid communication with a main combustion chamber.

[0109] This delicious, i. Operate a cracking device supplied with ammonia fuel to produce a cracked fuel containing a mixture of hydrogen and nitrogen. ii. Introducing fuel into the main combustion chamber, iii. Introducing the decomposed fuel from the decomposition device into the sub-combustion chamber. iv. Ignition of the fuel decomposed in the sub-combustion chamber to create a stream of combustion gases entering the main combustion chamber from the sub-combustion chamber, thereby igniting the fuel present in the main combustion chamber, and v. Using information received from sensor placements associated with the disassembled fuel or disassembled device to control the introduction of the disassembled fuel into the sub-combustion chamber (and / or control the operation of the disassembled device), which may include one or more of the above.

[0110] In the embodiment, the mixture of hydrogen and nitrogen further comprises undecomposed ammonia. Thus, the decomposed fuel may include a partially decomposed fuel comprising a mixture of hydrogen, nitrogen, and undecomposed ammonia. In the embodiment, the fuel introduced into the main combustion chamber comprises decomposed fuel from the decomposition device. In this case, the main combustion chamber may be fueled through the sub-combustion chamber in the manner discussed above.

[0111] Alternatively, the fuel introduced into the main combustion chamber may include ammonia fuel from an ammonia fuel source. In this case, the main combustion chamber may be fueled through a secondary combustion chamber in the manner discussed above. For example, the secondary combustion chamber may be equipped with an ammonia fuel injector adjacent to an injector for decomposed fuel. Alternatively, the main combustion chamber may be fueled through an intake port or by direct injection of ammonia fuel into the main combustion chamber.

[0112] In any embodiment of this method, the sensor comprises a pressure sensor, and the method includes receiving an indication from the pressure sensor of the decomposed fuel pressure being supplied to the fuel inlet. In embodiments, an electronically controlled device may determine whether the decomposed fuel pressure supplied to the fuel inlet is less than 10 bar, and if so, the method may include initiating the introduction of the decomposed fuel into the pre-combustion chamber during the intake stroke of the cylinder. This may advantageously allow the introduced fuel to be “drawn” into the main combustion chamber due to the decompression in the main combustion chamber that occurs during the intake stroke. Depending on the output pressure required for a typical decomposition device, it is conceivable that a decomposed fuel pressure of less than 10 bar may occur. The electronically controlled device may also initiate the introduction of the decomposed fuel into the pre-combustion chamber while the pressure is still relatively low during the start of the compression stroke.

[0113] In embodiments, if an electronic control device determines that the decomposed fuel pressure supplied to the fuel inlet exceeds 10 bar, the method may include initiating the introduction of the decomposed fuel into the pre-combustion chamber during the cylinder's compression stroke. When a pressurized pre-combustion fuel source, such as a pressurized hydrogen tank, is used, it is conceivable that a pre-combustion fuel pressure exceeding 10 bar may occur upstream of the pre-combustion fuel inlet.

[0114] In some cases, the injection of decomposed fuel can be delayed during the compression stroke until a predetermined level of compression is reached in the pre-combustion chamber. This can advantageously reduce the time it takes for turbulence in the injected spray of decomposed fuel to dissipate, thus maximizing turbulence at ignition and thereby improving combustion efficiency. Furthermore, delayed injection of decomposed fuel can typically reduce the compression work of the piston, thereby increasing the net work done.

[0115] According to a particular embodiment of this method, the sensor includes a sub-combustion chamber pressure sensor, and this method is i. This includes receiving an indication of the pressure in the pre-combustion chamber, and this method is performed during the compression stroke of the cylinder. ii. The process includes completing the introduction of pre-burned fuel into the sub-combustion chamber before the sub-combustion chamber pressure reaches a predetermined percentage of the pressure of the decomposed fuel supplied to the decomposed fuel inlet, as measured upstream of the fuel inlet.

[0116] In the embodiment, the pressure in the pre-combustion chamber is indicated by a pre-combustion pressure sensor. In the embodiment, a predetermined percentage is 50%. This method selects the injection timing such that the pre-combustion chamber pressure remains below half the supply pressure of the decomposed fuel during the injection period, which can facilitate the formation of a choke flow, and this is advantageous for reasons discussed below.

[0117] In some embodiments, the fuel inlet is equipped with a fuel injector, and this method includes the step of injecting fuel into a pre-combustion chamber during the compression stroke of the cylinder, and the injection timing of the decomposed fuel is selected to provide a choke flow condition across the decomposed fuel injector. In certain embodiments, an electronically controlled device operates the pre-combustion fuel injector to maintain a choke flow condition across the pre-combustion fuel injector throughout the entire duration of injection. It will be understood that the exact pressure drop across the pre-combustion fuel injector required to achieve the choke flow may vary depending on specific flow and fluid parameters. However, in many cases, a choke flow at the nozzle of a pre-combustion fuel injector can be assumed when the pressure upstream of the nozzle is more than twice the pressure downstream of the nozzle.

[0118] In certain embodiments, the decomposed fuel output by the decomposition device may be at a relatively low pressure, for example, in the range of 5 to 10 bar. In this case, the engine system of the present disclosure may be configured to achieve choke flow by timing the injection of the pre-combustion chamber when the pre-combustion chamber pressure is less than or equal to half the pre-combustion fuel pressure. In an example where the pre-combustion fuel output by the decomposition device is 5 bar, the electronic control unit may be configured to time the injection of the pre-combustion fuel when the pre-combustion chamber pressure is 2.5 bar or less.

[0119] The electronic control device may be configured to inject pre-combustion fuel when the sub-combustion chamber pressure is near or at the minimum level of the cycle. The electronic control device may be configured to inject pre-combustion fuel immediately before or simultaneously with the closing of the intake valve. The electronic control device may be configured to complete the injection before the sub-combustion chamber pressure reaches 50% of the broken-down fuel pressure. This is advantageous in that it can ensure that all pre-combustion fuel injection occurs under choke flow conditions, thereby avoiding partially chokeled and partially unchokeled injections, which may reduce the predictability and controllability of the injection.

[0120] The timing of sub-combustion chamber injection can be set based on real-time measured sub-combustion chamber pressure. Specifically, this timing can be set to achieve choke flow injection based on data received from a sub-combustion chamber pressure sensor.

[0121] Alternatively, the timing of pre-combustion chamber injection may be stored in the system and set based on a predetermined value of the pre-combustion chamber pressure available to the electronic control device. It will be understood that the engine system of this disclosure does not necessarily require real-time measurement of the pre-combustion chamber pressure to generate choke flow injection. The electronic control device may store a predetermined pre-combustion chamber pressure value as a function of the engine cycle. In low-pressure pre-combustion fuel injection scenarios, the electronic control device may be configured to determine the timing at which choke flow can be achieved by considering a predetermined value of the pre-combustion chamber pressure.

[0122] In a particular embodiment, this method is i. Evaluate the pressure of the decomposed fuel upstream of the fuel injector using real-time measurements of the decomposed fuel pressure from sensors associated with the decomposed fuel, ii. Evaluating the pressure inside the sub-combustion chamber by either using a predetermined value of the sub-combustion chamber pressure or by taking real-time measurements of the sub-combustion chamber pressure from a sub-combustion chamber pressure sensor, iii. Initiating the introduction of the decomposed fuel into the sub-combustion chamber via the decomposed fuel injector when the pressure of the decomposed fuel upstream of the decomposed fuel injector is at least twice the pressure in the sub-combustion chamber.

[0123] In a particular embodiment of this method, the electronic control device is configured to complete fuel injection into the sub-combustion chamber before the pressure in the sub-combustion chamber reaches half the pressure of the fuel being supplied to the sub-combustion chamber.

[0124] Embodiments of this method include the step of determining the injection timing of the decomposed fuel based on real-time measurements of the pressure of the decomposed fuel generated by the decomposition device and a predetermined value of the pressure in the pre-combustion chamber. The pre-combustion chamber pressure may be predetermined as a function of engine operating conditions and stored in an electronic control device. For example, the electronic control device may calculate or obtain an estimated pre-combustion chamber pressure based on engine operating conditions such as engine load, speed, and temperature.

[0125] Alternatively, this method may include the step of determining pre-combustion fuel injection timing based on real-time measurements of the pressure of the decomposed fuel generated by the decomposition device and real-time measurements of the pressure in the sub-combustion chamber. For example, this method may include the step of an electronically controlled device receiving a reading of the sub-combustion chamber pressure from a sub-combustion chamber pressure sensor.

[0126] In certain embodiments, the introduction of ammonia fuel into the main combustion chamber via an ammonia fuel injector may begin immediately before the combustion fluid stream enters the main combustion chamber from the sub-combustion chamber, such that a portion of the ammonia fuel injection period overlaps with the introduction period of the combustion fluid stream. The introduction of ammonia fuel into the main combustion chamber via an ammonia fuel injector may occur via a single continuous injection. Alternatively, the introduction of ammonia fuel into the main combustion chamber via an ammonia fuel injector may occur via multiple injections or "split" injections; that is, a certain amount of injected ammonia fuel may be shifted across two or more separate injection events.

[0127] In particular embodiments, i. Introducing a first spray of ammonia fuel into the main combustion chamber before the combustion gas stream enters the main combustion chamber from the sub-combustion chamber, ii. A method is provided which includes introducing a second spray of ammonia fuel into the main combustion chamber after a first spray of ammonia fuel has been substantially burned in the main combustion chamber.

[0128] In certain embodiments, this method includes the step of initiating and completing the injection of ammonia fuel into the main combustion chamber before the combustion gas stream enters the main combustion chamber from the sub-combustion chamber. The timing of the combustion fluid stream entering the main combustion chamber may depend on several parameters, such as ignition timing, engine load and speed, and turbulence. This timing may be predetermined as a function of these parameters using advanced optical visualization techniques and stored in an electronically controlled device. The timing of the combustion fluid stream may also be predicted based on the sub-combustion chamber pressure. Predetermined values ​​as a function of engine load and speed may be stored in the electronically controlled device and recalled when determining values ​​such as the ammonia fuel injection timing.

[0129] According to one embodiment, the step of introducing fuel into the main combustion chamber forms an air-fuel mixture that flows at least partially from the main combustion chamber to the sub-combustion chamber during the engine's compression stroke. The “backflow” of the air-fuel mixture flowing from the main combustion chamber to the sub-combustion chamber is advantageous in that it can supply air from the air-fuel mixture to the sub-combustion chamber, which facilitates the combustion of the decomposed fuel in the sub-combustion chamber.

[0130] In another aspect of the present disclosure, an internal combustion engine system is provided, the internal combustion engine system comprising: a cylinder having a main combustion chamber, an intake port and an exhaust port; a sub-combustion chamber having fluid communication with the main combustion chamber via at least one orifice, connected to a fuel source, and having a fuel inlet configured to allow the introduction of fuel from the fuel source to the sub-combustion chamber and to the main combustion chamber through the orifice; an ignition device positioned with the sub-combustion chamber and configured to ignite the fuel present in the sub-combustion chamber, wherein the sub-combustion chamber and / or the orifice are configured to allow the generation of a stream of combustion fluid entering the main combustion chamber from the sub-combustion chamber through the orifice, thereby enabling the ignition of the fuel present in the main combustion chamber; and an electronic control device configured to control the ignition device and to control the introduction of fuel into the sub-combustion chamber through the fuel inlet.

[0131] This aspect of the present disclosure advantageously enables fuel supply to the main combustion chamber via a sub-combustion chamber. For example, a predetermined amount of combustible fuel may be supplied to the main combustion chamber through an orifice connecting the main combustion chamber to the sub-combustion chamber. Therefore, the fuel introduced into the main combustion chamber via the sub-combustion chamber may be unburned and unignited. Thus, the main combustion chamber may be supplied with unburned fuel before the stream of combustion fluid enters the main combustion chamber, thereby igniting the unburned fuel present in the main combustion chamber.

[0132] This configuration is advantageous in that both the pre-combustion chamber and the main combustion chamber may be supplied with fuel through one or more inlets in the pre-combustion chamber. According to this aspect of the disclosure, the main combustion chamber can be supplied with combustible fuel through an orifice connecting the pre-combustion chamber to the main combustion chamber. This advantageously avoids the need for a separate fuel inlet to deliver fuel to the main combustion chamber. Supplying fuel to the main combustion chamber via the pre-combustion chamber avoids the need for a separate fuel injector located at the cylinder intake port (port injection) or the cylinder head (direct injection). This configuration may be particularly advantageous for two-stroke engines where there is a risk of fuel slip during exhaust scavenging.

[0133] According to a particular embodiment, the electronic control device is configured to introduce fuel into the sub-combustion chamber at a fuel flow rate that enables fuel supply to the main combustion chamber. The desired fuel flow rate can be selected by the electronic control device by changing the injection pressure and / or the injector flow area for a given engine load and speed requirement.

[0134] The stream of combustion fluid generated by the ignition of fuel may include a stream of combustion gas or combustion liquid, or a mixture thereof. The stream of combustion fluid may include a stream of combustion fuel. The stream of combustion fluid may include a flame jet. For example, a flame jet emerging from a sub-combustion chamber, which may contain a mixture of combustion gas, radicals, combustion and unburned fuel.

[0135] In certain embodiments, the fuel inlet may be equipped with a fuel injector. In certain embodiments, the fuel injector may be configured as a variable flow fuel injector. In certain embodiments, an electronic control device may be configured to adjust the flow rate of the fuel injector. In certain embodiments, the electronic control device may change an electronically operated waveform (e.g., a current waveform or a voltage waveform) that can change the movement of the injector needle. In this way, the electronic control device may adjust the flow area across the injector, and thus adjust the flow rate of the injector. This control method may be applied, for example, when the fuel injector is configured to allow a change in geometric area in response to the movement of the injector needle. In certain embodiments, the electronic control device is configured to control the injection pressure via an electronic pressure regulator.

[0136] In this aspect of the disclosure, the main combustion chamber may be fueled with the same type of fuel ignited in the secondary combustion chamber. In certain embodiments, at ignition, the fuel present in the main combustion chamber and the fuel present in the secondary combustion chamber are supplied through the same fuel inlet and from the same fuel source. The fuel may be a hydrogen-containing fuel. Alternatively, the fuel may be any other fuel or mixture of fuels suitable for use with the secondary combustion chamber.

[0137] In alternative embodiments, at ignition, the fuel present in the main combustion chamber is different from the fuel present in the secondary combustion chamber. The fuel burned in the secondary combustion chamber may be a relatively highly reactive fuel, while the fuel burned in the main combustion chamber may be a less reactive fuel. An example of a less reactive fuel may be ammonia. Examples of more reactive fuels (i.e., higher than ammonia) may include hydrogen, gasoline, diesel, natural gas, LPG, ethanol, and methanol. It will be understood that mixtures of these fuels may also be used.

[0138] In this embodiment, the sub-combustion chamber is equipped with an ammonia fuel injector configured to introduce ammonia fuel into the main combustion chamber through the sub-combustion chamber and through an orifice, and the engine further comprises a pre-combustion fuel injector connected to a source of pre-combustion fuel consisting at least partially of hydrogen, the pre-combustion fuel injector configured to introduce pre-combustion fuel into the sub-combustion chamber, and the ammonia fuel injector and the pre-combustion fuel injector communicate with and are controlled by an electronic control device. This configuration can advantageously utilize the higher reactivity of hydrogen as a pre-combustion fuel to generate an energy stream of combustion hydrogen entering the main combustion chamber from the sub-combustion chamber through the orifice in order to enhance the combustion of ammonia fuel in the main combustion chamber.

[0139] In this embodiment, the pre-combustion fuel injection, ammonia fuel injection, and ignition device are controlled by an electronic control device so that, at the time of ignition, the hydrogen mass in the sub-combustion chamber is higher than the hydrogen mass in the main combustion chamber.

[0140] The pre-combustion fuel may be supplied by a pressurized hydrogen tank. Alternatively, the hydrogen-containing pre-combustion fuel may be formed "in-situ" by a decomposition device. According to one embodiment, the engine further comprises a decomposition device connected to an ammonia fuel source and configured to produce a decomposed fuel containing a mixture of nitrogen and hydrogen by decomposing the ammonia fuel supplied by the ammonia fuel source during the operation of the engine, and the pre-combustion fuel includes the decomposed fuel received from the decomposition device. This can advantageously provide a source of hydrogen-containing pre-combustion fuel produced from the same ammonia fuel source used to supply fuel to the main combustion chamber.

[0141] In certain embodiments, the electronic control device is configured to control the injection timing and duration of the ammonia fuel injector and pre-combustion fuel injector to enable a hydrogen concentration in the sub-combustion chamber that is higher than the hydrogen concentration in the main combustion chamber during operation. Therefore, the electronic control device can be advantageously configured for the economic use of hydrogen supply or hydrogen-containing fuel, which may typically be less than or equal to ammonia fuel.

[0142] According to certain embodiments, an electronic control device communicates with a fuel sensor associated with a fuel source, and the electronic control device is configured to control the introduction of fuel through the fuel inlet according to measurements received from the fuel sensor. This can advantageously provide a fuel feedback loop, which may allow the electronic control device to optimize fuel introduction based on fuel characteristics that may change during engine operation. Examples of these changing characteristics may include fuel pressure, fuel temperature, and, in the case of pre-burned fuel supplied from a decomposition device, changing concentrations of gases in the decomposed fuel produced by the decomposition device.

[0143] In certain embodiments, the electronic control device is configured to control fuel delivery based on a predetermined indication of the pre-combustion chamber pressure and on real-time measurements of fuel pressure provided by a fuel sensor. The pre-combustion chamber pressure may be predetermined as a function of engine operating conditions and stored in the electronic control device. For example, the electronic control device may calculate or obtain an estimated pre-combustion chamber pressure based on engine operating conditions such as engine load, speed, and temperature. This may avoid the need for a pre-combustion pressure sensor, thereby reducing the overall number of sensors required for operation.

[0144] In an alternative embodiment, a pre-combustion pressure sensor may be used. For example, an electronic control device may be configured to control fuel delivery based on real-time measurements of the pre-combustion chamber pressure and the fuel pressure.

[0145] An engine according to this embodiment further comprises a compressor device configured to compress the decomposed fuel upstream of the pre-combustion chamber. In certain embodiments, the compressor device is configured to compress the decomposed fuel to a pressure below 100 bar. The compressor device may be configured to increase the pressure of the fuel supplied to the pre-combustion fuel inlet to facilitate choke flow across the pre-combustion fuel inlet. In embodiments in which the pre-combustion fuel inlet comprises a nozzle such as a pre-combustion fuel injector, the compressor device may be configured to compress the pre-combustion fuel to a pressure that allows choke flow across the nozzle. The compressor device may be controlled by an electronic control device.

[0146] In some embodiments, the internal combustion engine system includes a pressure booster injector. The pressure booster injector may comprise a fuel injector configured to compress gaseous fuel during injection using a hydraulically driven piston. In some embodiments, this configuration can advantageously increase fuel pressure without requiring a compressor device. The pressure booster injector may be controlled via high-speed hydraulic control, which controls the timing, speed, and amount of fuel injection. The pressure booster injector, or the hydraulic control device associated with the pressure booster injector, may be electronically controlled by an electronic control unit.

[0147] One aspect of this disclosure may relate to a power generation system comprising an internal combustion engine system according to one of the embodiments discussed above.

[0148] Another aspect of the present disclosure provides a method for supplying fuel to an internal combustion engine having a sub-combustion chamber that is in fluid communication with a main combustion chamber via an orifice, the method comprising introducing fuel into the main combustion chamber by injecting fuel into the sub-combustion chamber using injection parameters configured to create a fuel flow path from the sub-combustion chamber through the orifice into the main combustion chamber.

[0149] In the embodiment, the injection parameters include at least one of the injection mass flow rate, injection pressure, and injection timing.

[0150] In the embodiment, the fuel is supplied from a fuel source, and this method is i. Measuring one or more characteristics of a fuel source using one or more fuel sensors associated with the fuel source, ii. Communicating the measured characteristics of the fuel source to an electronic control device configured to communicate with a sensor and control the introduction of fuel into the sub-combustion chamber, iii. Further comprising determining injection parameters based on the measured characteristics of the fuel source using an electronically controlled device.

[0151] In embodiments of this disclosure, injection parameters include injection timing and injection duration. Measurements communicated from one or more fuel sensors may include at least one of the pressure and temperature of the fuel source. Measurements communicated from one or more fuel sensors may also include compositional information relating to the fuel source. For example, if a hydrogen-containing fuel mixture is used as fuel, measurements communicated from one or more fuel sensors may include hydrogen concentration.

[0152] In the embodiment, the fuel introduced into the main combustion chamber via injection into the sub-combustion chamber includes the main combustion chamber fuel, and the method includes the step of introducing a pre-combustion fuel having a different composition from the main fuel into the sub-combustion chamber. For the reasons discussed above, this may advantageously allow the use of a more reactive fuel to facilitate the combustion of a less reactive fuel.

[0153] In some embodiments, the introduction of pre-combustion fuel into the sub-combustion chamber begins after the introduction of main combustion chamber fuel into the main combustion chamber. In some embodiments, the main combustion chamber fuel includes ammonia fuel, and the sub-combustion chamber fuel includes hydrogen-containing fuel. The hydrogen-containing fuel may be supplied at least partially from a hydrogen tank.

[0154] In this embodiment, the method is i. To provide an ammonia fuel supply source, ii. Operating a cracking device supplied by an ammonia fuel source to produce a cracked fuel containing a mixture of hydrogen and nitrogen, iii. Further comprising supplying the decomposed fuel produced by the decomposition device to a sub-combustion chamber for use as a hydrogen-containing fuel.

[0155] In certain embodiments, the ammonia fuel introduced into the main combustion chamber is supplied by an ammonia fuel source that feeds the cracking device. This can advantageously allow the use of multiple fuel types, originating from a single ammonia fuel source, such as an ammonia fuel tank that supplies both the main combustion chamber and the cracking device.

[0156] A further aspect of this disclosure provides a method for modifying an internal combustion engine cylinder, the method being: i. Mounting a sub-combustion chamber to a cylinder, including connecting the downstream end of the sub-combustion chamber to the fuel inlet of the cylinder in order to provide fluid communication between the sub-combustion chamber and the main combustion chamber in the cylinder, wherein the sub-combustion chamber is equipped with an ignition device configured to allow ignition of fuel in the sub-combustion chamber during operation. ii. Including connecting the fuel supply source to the fuel inlet of the sub-combustion chamber.

[0157] This aspect of the present disclosure may, advantageously, enable the conversion of a conventional internal combustion engine cylinder to use a sub-combustion chamber for improved engine performance. The sub-combustion chamber may include the sub-combustion chamber described in any of the aforementioned embodiments of the present disclosure.

[0158] In certain embodiments, a sub-combustion chamber may be configured to introduce fuel to the main combustion chamber through the sub-combustion chamber during operation. The sub-combustion chamber used in this modification method enables fuel supply to the main combustion chamber through the sub-combustion chamber. This may advantageously allow the sub-combustion chamber to be mounted on the fuel inlet of an existing cylinder, and may allow both the sub-combustion chamber and the main combustion chamber to be fueled through a single fuel inlet.

[0159] In another embodiment, the cylinder may include a main chamber fuel injector configured to introduce fuel into the main combustion chamber either through an intake port communicating with the main combustion chamber or through direct injection into the main combustion chamber.

[0160] The method of modifying an engine to include a pre-combustion chamber as described above may further include modifying the cylinder head of a cylinder to accommodate the pre-combustion chamber. The method may further include connecting the pre-combustion chamber to a decomposition device configured to supply the pre-combustion chamber with decomposed fuel, including hydrogen and ammonia. The method may further include installing additional components, which may include an ammonia supply tank, a pump, an evaporator, a heat exchanger, a decomposed gas injector, and a new ignition system. The method may further include installing an electronic control device, or remapping an existing electronic control device with maps for ignition timing, injection duration, and injection timing, which can be optimized as a function of engine load and speed, and optionally, for emissions reduction and efficiency.

[0161] A sub-combustion chamber may be configured with a single fuel inlet. In this embodiment, the sub-combustion chamber and the main combustion chamber may be fueled by the same fuel type. Combustion of a single fuel type may be enhanced by the use of a sub-combustion chamber, which may generate one or more streams of combustion fluid that extend from the sub-combustion chamber into the main combustion chamber, promoting improved combustion of the fuel present in the main combustion chamber.

[0162] A sub-combustion chamber may be configured with two inlets, one configured for use with a relatively low-reactivity fuel and the other for use with a higher-reactivity fuel. Suitable examples of lower-reactivity and higher-reactivity fuels, as discussed above, may include, for example, ammonia fuel and hydrogen-containing fuel. The use of a "multiple-inlet" sub-combustion chamber may make it possible to provide two fuel types to a cylinder originally designed for a single fuel type. Advantageously, a method according to this embodiment of the disclosure may make it possible to convert a diesel engine into an ammonia-fueled engine, which has a sub-combustion chamber fueled by hydrogen-containing fuel to facilitate the combustion of ammonia fuel supplied to the main combustion chamber of the cylinder.

[0163] It will be understood that the engines according to this disclosure are not necessarily limited to use with a disassembly device. Some embodiments of this disclosure may operate using different hydrogen sources for pre-combustion fuel. For example, in embodiments of this disclosure, the supply of pre-combustion fuel is obtained at least partially from a hydrogen storage tank. In certain embodiments, the pre-combustion fuel contains at least 90 volume percent hydrogen.

[0164] The use of hydrogen tanks or similar pressurized vessels can, advantageously, allow pre-combustion fuel to be supplied at high pressure (approximately 100–200 bar) or low pressure (approximately 5–50 bar). Low-pressure injection may be preferable in some applications due to increased cost-effectiveness. High-pressure injection may offer increased thermal efficiency, which will be discussed in more detail in subsequent paragraphs.

[0165] In certain forms of this disclosure, the pre-combustion fuel injection may be configured to perform both high-pressure and low-pressure injection. This may, advantageously, allow the high-pressure injection to occur when the hydrogen tank is fully full, and the low-pressure injection to occur when the hydrogen tank is depleted.

[0166] For example, if the hydrogen tank pressure is greater than the high-pressure injection range, the pre-combustion fuel injector may operate at a set pressure within that range. If the hydrogen tank pressure falls below the high-pressure injection range, the injector may operate at a tank pressure such that the injection pressure correlates with the tank pressure when the hydrogen tank is depleted.

[0167] According to a particular embodiment, a hydrogen pressure regulator is used in a fuel line to control the pressure of pre-combustion fuel supplied to a pre-combustion fuel injector according to a preferred operating pressure. In a particular embodiment, hydrogen pressure and temperature sensors can be incorporated into the regulator module. Thereafter, the module can function within a feedback loop, thus enabling precise control of hydrogen injection amount and good combustion stability.

[0168] In embodiments of the present disclosure in which a hydrogen tank is used (and therefore the hydrogen concentration in the pre-combustion fuel supply source is unlikely to change), it will be understood from the above that the pre-combustion fuel supply sensor is advantageous in that it can provide real-time measurement of the pre-combustion fuel pressure, enabling an electronic control device to determine the optimal pre-combustion fuel injection timing and duration based on specific engine load and speed requirements.

[0169] According to a particular embodiment, the pre-combustion fuel comprises a mixture of hydrogen and methane, the mixture containing at least 50 volume percent hydrogen. For example, the engine may include a pre-combustion fuel tank containing a pre-mixed hydrogen / methane mixture such as hytan.

[0170] According to embodiments of the present disclosure, an ammonia-fueled internal combustion engine system is provided, which is connectable to an ammonia fuel source and configured to produce a decomposed fuel comprising a mixture of nitrogen and hydrogen by decomposing ammonia fuel supplied by the ammonia fuel source during engine operation; a main combustion chamber and a sub-combustion chamber having fluid communication with the main combustion chamber via at least one orifice, and further comprising a decomposed fuel inlet for enabling the introduction of decomposed fuel supplied from the decomposition device into the sub-combustion chamber; and a decomposed fuel being operably positioned together with the sub-combustion chamber. An ignition device configured to ignite fuel in a sub-combustion chamber, wherein the sub-combustion chamber and / or orifice are configured to generate a stream of combustion fluid from the sub-combustion chamber to the main combustion chamber via the orifice when the decomposed fuel is ignited in the sub-combustion chamber, enabling ignition of fuel present in the main combustion chamber; a sensor arrangement configured to measure the characteristics of the decomposed fuel; and an electronic control device communicating with the sensor arrangement and the ignition device, configured to evaluate the characteristics of hydrogen present in the decomposed fuel using measurements received from the sensor arrangement, and to control the introduction of the decomposed fuel into the sub-combustion chamber according to the evaluated characteristics of the hydrogen.

[0171] In another aspect of the present disclosure, an ammonia-fueled internal combustion engine is provided, the ammonia-fueled internal combustion engine comprising: a main combustion chamber, an intake valve, an exhaust valve, and a main fuel injector connected to a source of ammonia fuel and configured to introduce ammonia fuel into the main combustion chamber; a sub-combustion chamber having fluid communication with the main combustion chamber via at least one orifice and connected to a source of pre-combustion fuel consisting of partially pre-combustion fuel, comprising a pre-combustion fuel injector and an ignition device configured to ignite the pre-combustion fuel introduced into the sub-combustion chamber via the pre-combustion fuel injector, wherein the ignition in the sub-combustion chamber generates a flame jet entering the main combustion chamber via at least one orifice to facilitate or induce ignition of ammonia fuel in the main combustion chamber; and an electronic control device electronically communicating with a pre-combustion fuel sensor configured to measure the characteristics of the main fuel injector, the pre-combustion fuel injector, and the pre-combustion fuel supply, and configured to control the operation of the main fuel injector and the pre-combustion fuel injector according to the display of pre-combustion fuel characteristics received from the pre-combustion fuel sensor.

[0172] The engines described herein are advantageously configured to operate the pre-burn fuel injectors and main injectors based on a display of pre-burn fuel characteristics. The pre-burn fuel sensors may be configured to provide a real-time display of pre-burn fuel characteristics, which helps to inform the optimized injection of main and pre-burn fuel into the main and sub-combustion chambers, respectively. Thus, pre-burn fuel injection, main fuel injection, and ignition timing can be optimized according to the real-time characteristics of the pre-burn fuel.

[0173] A pre-combustion fuel sensor may be configured to provide a real-time display of the pre-combustion fuel upstream of the pre-combustion fuel injector. The pre-combustion fuel sensor may be configured to provide a real-time display of the pre-combustion fuel pressure. The pre-combustion fuel sensor may be configured to provide a real-time display of the pre-combustion fuel temperature. The pre-combustion fuel sensor may be configured to provide a real-time display of the hydrogen concentration of the pre-combustion fuel. The pre-combustion fuel sensor may be configured to provide a real-time display of the pre-combustion fuel pressure, temperature, and hydrogen concentration.

[0174] According to the embodiment, the electronic control device controls the volume of hydrogen introduced into the sub-combustion chamber via the pre-combustion fuel injector and the volume of ammonia introduced into the main combustion chamber via the main fuel injector, and the electronic control device controls the main fuel injector and the pre-combustion fuel injector so that the ratio of the hydrogen volume to the ammonia volume is within a preferred range.

[0175] According to one embodiment, the electronic control device is configured to introduce a volume of hydrogen, which is 5% to 25% of the volume of ammonia introduced into the main combustion chamber via the main fuel injector, into the sub-combustion chamber via the pre-combustion fuel injector. According to another embodiment, the electronic control device determines the volume of ammonia introduced into the main combustion chamber as a function of the volume of hydrogen available for introduction into the sub-combustion chamber. A pre-combustion fuel sensor, according to another embodiment, is configured to measure the concentration, pressure, and temperature of hydrogen in the pre-combustion fuel supply source.

[0176] According to the embodiment, for each engine cycle, the electronic control device is responsible for the following sequence of actions: determining the engine load and engine speed requirements; determining the pressure, temperature, and concentration of hydrogen in the pre-combustion fuel supply source via a pre-combustion fuel sensor; setting the timing and duration of the pre-combustion fuel injector; setting the timing and duration of the main fuel injector; and setting the ignition timing of the ignition device in the sub-combustion chamber. According to the embodiment, the engine further comprises a catalytic cracking device in fluid communication with the pre-combustion fuel injector, which is supplied with an ammonia fuel supply, and the pre-combustion fuel supply obtained from the catalytic cracking device contains a mixture of hydrogen and nitrogen. According to the embodiment, the mixture of nitrogen and hydrogen obtained from the catalytic cracking device is supplied to the pre-combustion fuel injector without undergoing a separation process.

[0177] According to the embodiment, the mixture of hydrogen and ammonia obtained from the catalytic cracking device contains at least 50 volume percent hydrogen. According to the embodiment, the catalytic cracking device is supplied by an ammonia fuel source connected to the main injector. According to the embodiment, a pre-combustion fuel sensor is configured to detect the hydrogen properties in the mixture of hydrogen and ammonia obtained from the catalytic cracking device. According to the embodiment, the catalytic cracking device is in thermal communication with the waste heat generated by the engine.

[0178] According to the embodiment, the catalytic decomposition device comprises an electric heating element. According to the embodiment, the supply of pre-combustion fuel is obtained at least partially from a hydrogen storage tank, and the pre-combustion fuel contains at least 90 volume percent hydrogen. According to the embodiment, the pre-combustion fuel comprises a mixture of hydrogen and methane, the mixture containing at least 50 volume percent hydrogen. According to the embodiment, the sub-combustion chamber includes a coating of catalytic material configured to partially convert ammonia introduced into the cylinder into hydrogen. According to the embodiment, the catalytic material is coated on the inner wall of the combustion chamber and / or on the surface of at least one orifice.

[0179] According to the embodiment, the ignition device is a spark plug or a glow plug. According to the embodiment, at least one orifice has a diameter of 0.8 mm to 3.0 mm. According to the embodiment, the sub-combustion chamber is in fluid communication with the main combustion chamber through a plurality of orifices configured to generate a plurality of flame jets in the main combustion chamber. According to the embodiment, the cylinder comprises a cylinder head, and the sub-combustion chamber is located on the cylinder head. According to the embodiment, the volume of the sub-combustion chamber is at least 3% of the clearance volume of the cylinder. According to the embodiment, the pre-combustion fuel sensor is located upstream of the pre-combustion fuel injector, and the electronic control device receives an indication from the pre-combustion fuel sensor of the pre-combustion fuel pressure supplied to the pre-combustion fuel injector.

[0180] According to one embodiment, if the indicated pressure of the pre-combustion fuel supplied to the pre-combustion fuel injector is less than 10 bar, the electronic control device starts introducing the pre-combustion fuel into the sub-combustion chamber during the intake stroke of the cylinder and when the intake valve is in the open position. According to another embodiment, if the indicated pressure of the pre-combustion fuel supplied to the pre-combustion fuel injector exceeds 100 bar, the electronic control device starts introducing the pre-combustion fuel into the sub-combustion chamber during the compression stroke of the cylinder and when the intake valve is in the closed position. According to yet another embodiment, the electronic control device is configured to receive a reading of the pressure in the sub-combustion chamber from a sub-combustion chamber pressure sensor, and during the compression stroke of the cylinder, when the sub-combustion chamber pressure reaches half the indicated pressure of the pre-combustion fuel supplied to the pre-combustion fuel injector, the electronic control device starts introducing the pre-combustion fuel into the sub-combustion chamber.

[0181] According to one embodiment, the engine further comprises a pre-combustion fuel buffer tank located upstream of the pre-combustion fuel injector and configured to buffer the supply of pre-combustion fuel provided to the pre-combustion fuel injector. According to one embodiment, an electronic control device is configured to inject pre-combustion fuel into a sub-combustion chamber during the compression stroke of the cylinder, and the injection timing of the pre-combustion fuel is selected to provide a choke flow condition across the pre-combustion fuel injector. According to one embodiment, the electronic control device selects the injection timing of the pre-combustion fuel based on real-time measurement of the pressure in the pre-combustion fuel supply source and a predetermined value of the pressure in the sub-combustion chamber. According to one embodiment, the electronic control device selects the injection timing of the pre-combustion fuel based on real-time measurement of the pressure in the pre-combustion fuel supply source and a real-time measurement of the pressure in the sub-combustion chamber.

[0182] According to one embodiment, injection of pre-combustion fuel occurs while the pressure of the pre-combustion fuel upstream of the pre-combustion fuel injector is at least twice the pressure in the sub-combustion chamber. According to another embodiment, the main fuel injector is configured for the direct injection of ammonia fuel into the main combustion chamber. According to another embodiment, a first portion of the ammonia fuel introduced into the main combustion chamber is injected just before the flame jet enters the main chamber from the sub-combustion chamber, and a second portion of the ammonia fuel is injected after the first portion has been substantially burned by the flame jet in the main chamber. According to yet another embodiment, the injection of ammonia fuel introduced into the main combustion chamber is completed just before the flame jet enters the main combustion chamber from the sub-combustion chamber. According to yet another embodiment, the main fuel injector begins injecting ammonia fuel into the main combustion chamber just before the flame jet enters the main combustion chamber.

[0183] In this specification, references to “real-time” measurement and “real-time” display will be understood as a display or measurement performed by a sensor during engine operation and communicated to an electronically controlled device. The sensor may typically perform periodic measurements of relevant features at a specific sample rate. The specific sample rate required may vary depending on the type of measurement performed, but may typically be selected to allow detection of changes in the measured features occurring during engine operation. In certain embodiments, the pressure in the pre-combustion chamber and / or main combustion chamber may be measured in real time as a function of the crank angle and with a resolution of 1 to 5 degrees. In certain embodiments, the real-time pressure measurement is performed with a resolution of 1 degree. Real-time measurements of fuel pressure, fuel temperature, and hydrogen concentration may be performed using commercially available sensors, typically with resolutions used in automotive applications. For example, one or more real-time measurements of fuel pressure, fuel temperature, and hydrogen concentration may be performed in the range of once every 1 to 5 engine cycles. It will be understood that the engine systems according to this disclosure may be implemented using conventional fuel sensors and do not require special sensors configured for high sampling rates.

[0184] Advantageously, the engine according to this embodiment of the present disclosure is suitable for use with a pre-combustion fuel containing a mixture of hydrogen and non-hydrogen. This is in contrast to previous engines configured for use with a pre-combustion fuel supply of relatively high-purity hydrogen, in which the engine can assume that the majority or all of the injected pre-combustion fuel contains hydrogen. The feedback loop enables operation without necessarily requiring a bulky, heavy, and regularly replenished source of high-purity hydrogen (typically one or more hydrogen tanks).

[0185] Feedback provided by pre-combustion fuel sensors within the pre-combustion fuel supply source can improve engine robustness and allow for the use of hydrogen fuel mixtures in various proportions from sources such as industrial waste and steam methane reforming. For example, hydrogen can also be blended with other gaseous fuels such as natural gas. The flexibility in tolerating varying levels of purity in the hydrogen mixture offers significant economic advantages.

[0186] According to one aspect of the present disclosure, an ammonia fuel internal combustion engine system is provided, the ammonia fuel internal combustion engine system is connectable to an ammonia fuel supply source and configured to produce a decomposed fuel comprising a mixture of nitrogen and hydrogen by decomposing ammonia fuel supplied by the ammonia fuel supply source during engine operation; a main combustion chamber and a sub-combustion chamber having fluid communication with the main combustion chamber via at least one orifice, and further comprising a decomposed fuel inlet for enabling the introduction of decomposed fuel supplied from the decomposition device into the sub-combustion chamber; and a device operably positioned together with the sub-combustion chamber to introduce the decomposed fuel into the sub-combustion chamber. An ignition device configured to ignite in a combustion chamber, wherein the sub-combustion chamber and / or orifice are configured to generate a stream of combustion fluid from the sub-combustion chamber to the main combustion chamber via the orifice when the decomposed fuel is ignited in the sub-combustion chamber, enabling ignition of the fuel present in the main combustion chamber; a sensor arrangement configured to measure the characteristics of the decomposed fuel and / or the decomposition device; and an electronic control device communicating with the sensor arrangement and the ignition device, configured to evaluate the characteristics of the hydrogen present in the decomposed fuel using the measurements received from the sensor arrangement, and to control the introduction of the decomposed fuel into the sub-combustion chamber according to the evaluated characteristics of the hydrogen. [Brief explanation of the drawing]

[0187] To allow this disclosure to be more fully understood, several embodiments will be described with reference to the following drawings.

[0188] [Figure 1] An engine system according to an embodiment of this disclosure will be illustrated as an example. [Figure 2] An alternative engine system to the one in Figure 1, where the ammonia fuel injector is configured for direct injection, is illustrated. [Figure 3] An embodiment of a sub-combustion chamber suitable for use in conjunction with any of the embodiments illustrated and described herein is illustrated. [Figure 4] The following examples illustrate sequences of actions performed by electronically controlled devices according to embodiments of this disclosure. [Figure 5] An engine system according to a further embodiment of the present disclosure will be illustrated. [Figure 6] An engine system according to a further embodiment of the present disclosure will be illustrated. [Figure 7] Figure 6 illustrates an alternative embodiment of the engine system in which the main fuel injector is configured for direct injection. [Figure 8] An engine system according to an alternative embodiment of the present disclosure is illustrated. [Figure 9] An engine system according to an alternative embodiment of the present disclosure is illustrated. [Figure 10] An engine system according to an alternative embodiment of the present disclosure is illustrated. [Figure 11] An engine system according to an alternative embodiment of the present disclosure is illustrated. [Figure 12] This disclosure illustrates injection and ignition timing diagrams for various engine system embodiments. [Figure 13] This disclosure illustrates injection and ignition timing diagrams for various engine system embodiments. [Figure 14] This disclosure illustrates injection and ignition timing diagrams for various engine system embodiments. [Figure 15]This disclosure illustrates injection and ignition timing diagrams for various engine system embodiments. [Figure 16] This disclosure illustrates injection and ignition timing diagrams for various engine system embodiments. [Figure 17] An exemplary schematic diagram of a fuel system for use with various engine system embodiments described herein is illustrated. [Figure 18] An exemplary schematic diagram of a fuel system for use with various engine system embodiments described herein is illustrated. [Figure 19] An exemplary schematic diagram of a fuel system for use with various engine system embodiments described herein is illustrated. [Figure 20] An exemplary schematic diagram of a fuel system for use with various engine system embodiments described herein is illustrated. [Figure 21] An exemplary schematic diagram of a fuel system for use with various engine system embodiments described herein is illustrated. [Figure 22] An exemplary schematic diagram of a fuel system for use with various engine system embodiments described herein is illustrated. [Figure 23] An exemplary schematic diagram of a fuel system for use with various engine system embodiments described herein is illustrated. [Modes for carrying out the invention]

[0189] Figures 1 and 2 illustrate an ammonia fuel engine system 1 according to a first embodiment of the present disclosure. The engine 1 has a cylinder 10 with a piston 12 in a main combustion chamber 14. The cylinder 10 has an intake port with an intake port 16 and an exhaust port with an exhaust port 18. The intake port 16 and the exhaust port 18 are fluidly connected to the main combustion chamber 14 in the cylinder head 24. The intake port 16 and the exhaust port 18 can be selectively closed by an intake valve 20 and an exhaust valve 22, respectively, and are also located in the cylinder head 24.

[0190] A main fuel injector 26, equipped with an ammonia fuel injector, is located at the intake port 16 and connected to an ammonia fuel supply source 28. The main fuel injector 26 is configured to deliver ammonia fuel to the intake port 16, and a mixture of ammonia fuel and air is supplied to the main combustion chamber 14 via the intake valve 20. In the illustrated embodiment, this is shown to occur during the intake stroke. However, in some cases, ammonia fuel may be delivered via the main fuel injector 26 and the intake valve 20 during the compression stroke.

[0191] The cylinder 10 further comprises a sub-combustion chamber 30 located in the cylinder head 24 and in fluid communication with the main combustion chamber 14 via a plurality of orifices 32. The main combustion chamber 14 and the sub-combustion chamber 30 are in fluid communication (e.g., constant fluid communication) via the plurality of orifices 32. The sub-combustion chamber 30 further comprises an ignition device, in this example, comprising a spark plug 38 configured to ignite pre-combustion fuel delivered to the sub-combustion chamber 30 via a pre-combustion fuel injector 34.

[0192] The sub-combustion chamber 30 has a fuel inlet, which includes a pre-combustion fuel injector 34 connected via a pre-combustion fuel line 44, as shown in Figure 1.

[0193] The engine system 1 further comprises an ammonia cracking device 46 that receives ammonia fuel from an ammonia fuel source 28 via an ammonia supply line 48. The spatial positioning of the cracking device 46 can vary. The cracking device 46 may be positioned relatively close to the cylinder 10. For example, both the cracking device 46 and the cylinder 10 may be housed in the engine compartment of a vehicle. Alternatively, the cracking device 46 may be positioned away from the cylinder 10. For example, the cracking device 46 may be positioned outside the engine compartment of a vehicle that houses the cylinder 10. It should be understood that the cracking device 46, regardless of its spatial positioning relative to the cylinder 10, forms part of the same engine system 1 as the cylinder 10. It should also be understood that the engine system 1 does not have to be a vehicle engine and can be used with any power generation device, which may be variable speed / load or generally fixed speed / load (e.g., a power generation set, whether containerized or not). In some examples, the engines described herein may be used, for example, as automobile engines, marine engines, power generation units, motorcycle engines, aircraft engines, locomotive engines, or for any other internal combustion engine applications. In some examples, the engines may have power ratings of kW to MW.

[0194] The output of the ammonia decomposition device 46, which is produced by chemical decomposition, is a decomposed fuel containing a mixture of hydrogen and nitrogen. The decomposed fuel mixture may also contain undecomposed ammonia, depending on the operating conditions of the decomposition device (e.g., the efficiency of the decomposition device). The decomposed fuel is delivered to the decomposed fuel injector 34 via the pre-combustion fuel line 44. The decomposed fuel is introduced into the sub-combustion chamber 30 via the pre-combustion fuel injector 34. Thus, in this embodiment, the pre-combustion fuel injector 34 comprises a decomposed fuel injector. The decomposed fuel is introduced into the sub-combustion chamber without any separation or filtration. Thus, the cylinder 10 is configured to use a mixture of nitrogen and hydrogen (and potentially undecomposed ammonia) as a pre-combustion fuel introduced into the sub-combustion chamber 30.

[0195] The cylinder 10 is associated with an electronically controlled device comprising an electronically controlled unit (ECU) 40 that electronically communicates with a main fuel injector 26, a pre-combustion fuel injector 34, and a spark plug 38. The ECU 40 forms part of the engine system 1, but, like the disassembly device 46, the positioning of the ECU 40 relative to the cylinder 10 may vary depending on the application of the engine system 1.

[0196] The ECU 40 is configured to evaluate one or more characteristics of the decomposed fuel using measurements received from a sensor arrangement 42 associated with the decomposed fuel or decomposed device 46. In the embodiment shown in Figure 1, the sensor is part of a sensor pack 42 positioned in the pre-combustion fuel line 44 upstream of the pre-combustion fuel injector 34. Specifically, the sensor pack 42 is positioned between the decombustion device 46 and the pre-combustion fuel injector 34. The ECU 40 is configured to receive measurements from the sensor pack 42 and evaluate the characteristics or properties of the decomposed fuel supplied to the pre-combustion fuel injector 34. In certain embodiments, the characteristics include the pressure and temperature of the decomposed fuel. In certain embodiments, the characteristics include the pressure and temperature of the decomposed fuel as well as the hydrogen concentration.

[0197] The ECU 40 is configured to control the introduction of the decomposed fuel into the sub-combustion chamber 30 by electronically operating the pre-combustion fuel injector 34. The ECU 40 is configured to introduce a spray of pre-combustion fuel into the sub-combustion chamber 30. The ECU is configured to control the duration and timing of the spray of decomposed fuel introduced into the sub-combustion chamber 30. The ECU is further configured to control the operation of the main fuel injector 26 and the spark plug 38 according to the evaluated hydrogen characteristics of the decomposed fuel supplied to the pre-combustion fuel injector 30.

[0198] The sensor pack 42 measures the characteristics of the pre-combustion fuel (for example, continuously) to determine the timing and duration of main fuel injection and pre-combustion fuel injection, as well as the ignition timing. In the embodiment shown in Figure 1, the hydrogen concentration in the pre-combustion fuel may be due to factors such as the temperature of the decomposition device 46, along with the efficiency of the decomposition device 46.

[0199] The embodiment illustrated in Figure 1 is advantageous in that it can generate hydrogen-containing cracked fuel "on-site" as part of the engine system. Furthermore, the ammonia fuel supply for the main fuel injector 26 and the cracked fuel supply for the pre-combustion injector 34 are both supplied from the same ammonia fuel source 28. This eliminates the need for a separate hydrogen source, such as a hydrogen tank. The cracking device 46 may be designed to generate the required amount of hydrogen on demand, depending on the engine load and speed, and is therefore directly connected to the fuel system of the pre-combustion chamber, as shown in the figure. The energy required for the process can also be advantageously obtained from the engine's waste heat. In certain embodiments, the ECU 40 acts on the pre-combustion chamber injector 34 based on the operating pressure of the cracking device 46.

[0200] In the embodiment illustrated in Figure 1, the pre-combustion fuel injector 34 is shown to be configured for direct injection into the sub-combustion chamber 30. However, it should be understood that in alternative configurations, the pre-combustion fuel injector 34 may be located upstream of the sub-combustion chamber 30 and connected to it via a passage. In some alternative embodiments, the pre-combustion fuel injector 34 is located upstream of the sub-combustion chamber and is in fluid communication with the sub-combustion chamber via a fuel line that includes a backflow prevention check valve.

[0201] The hydrogen and nitrogen mixture (i.e., decomposed fuel) output by the decomposition device 46 can typically be at a relatively low pressure (less than approximately 20 bar). As illustrated in Figure 1, the pre-combustion fuel injection may be configured to occur during the intake stroke of the cylinder 10, when the piston 12 is moving downward and the intake valve 20 is in the open position. During the compression stroke, the upward movement of the piston 12 can push some of the ammonia-air mixture from the main combustion chamber 14 into the sub-combustion chamber 30. Thus, at ignition, both the main combustion chamber 14 and the sub-combustion chamber 30 can contain ammonia fuel and hydrogen-containing decomposed fuel. The sub-combustion chamber 30 may contain a higher proportion of hydrogen than the main combustion chamber 14. The different proportions of hydrogen and ammonia are advantageous, as fast-burning hydrogen molecules are surrounded by slow-burning ammonia molecules, which can result in smoother combustion speeds and pressure increases in both chambers.

[0202] Therefore, the embodiment shown in Figure 1 illustrates low-pressure injection of decomposed fuel into the pre-combustion chamber 30, where the fuel pressure upstream of the pre-combustion fuel injector 34 may be less than 20 bar. In some cases, the decomposed fuel pressure upstream of the pre-combustion fuel injector 34 may be less than 10 bar. The ECU 40 controls the operation of the injectors 26, 34 and the ignition device 38. The ECU 40 may receive real-time measurements of the fuel pressure upstream of the pre-combustion chamber injector 34 from the sensor pack 42. In some configurations, when the measured pressure is approximately 10 bar or less, the ECU 40 activates the pre-combustion fuel injector 34 to initiate injection of hydrogen-containing decomposed fuel during the opening period of the intake valve 20, as shown in Figure 1.

[0203] The method of low-pressure injection of the decomposed fuel into the sub-combustion chamber 30 may, in some cases, advantageously allow the injected decomposed fuel to diffuse into the main chamber 14 through the orifice 32 and mix with the main ammonia fuel, depending on the local pressure and velocity. The ECU 40 also operates the main fuel injector 26 located in the intake port 16 when the intake valve 20 is open, as shown in Figure 1, to inject ammonia fuel into the main combustion chamber 14.

[0204] As will be discussed later with reference to Figures 6, 8, and 17-23, in some embodiments of the present disclosure, the fuel supply to the pre-combustion chamber may be provided at a higher pressure, in which case the ECU 40 may employ a different injection strategy than the low-pressure injection method described above. For example, the pre-combustion fuel supply may be provided by a pressurized tank. Alternatively, the engine system may further include a compressor device for increasing the pressure of the decomposed fuel upstream of the pre-combustion chamber.

[0205] Referring to Figure 2, an engine system 2 comprising a cylinder 200 is illustrated according to an alternative embodiment of the present disclosure. The cylinder 200 is similar to the cylinder 10 illustrated in Figure 1, except that the main fuel injector 26 is configured in the cylinder 200 for direct injection into the main combustion chamber 14. Providing the main fuel injector 26 as a direct injector can advantageously enable the direct injection of ammonia fuel into the main combustion chamber 14 at any time during the intake and compression strokes of the cylinder.

[0206] The main fuel injector 26 of cylinder 200 is located on the cylinder head 24. Therefore, the main fuel injector 26 is positioned adjacent to the sub-combustion chamber 30 on the cylinder head 24. In the embodiments illustrated in Figures 1 and 2, the main fuel injector 26 is configured to introduce fuel into the main combustion chamber independently of the sub-combustion chamber 30.

[0207] It will be understood that the intake port 16 of cylinder 200 in Figure 2 can supply air to the main combustion chamber 14 to form the air-fuel mixture in the main combustion chamber 14 during injection by the main fuel injector 26 while in use. In contrast, the intake port 16 of cylinder 10 in Figure 1 provides the air-fuel mixture to the main combustion chamber 14.

[0208] According to embodiments of the present disclosure, the ECU 40 is configured to operate the main fuel injector 26 and the pre-combustion fuel injector 34 to introduce a volume of decomposed fuel corresponding to the volume of hydrogen (depending on the hydrogen concentration of the decomposed fuel) into the sub-combustion chamber, and to introduce a volume of ammonia within a target range into the main combustion chamber (e.g., during normal operating conditions). In certain embodiments, the ECU 40 is configured with a target concentration of hydrogen volume of 5% to 35% relative to the ammonia fuel volume. In certain embodiments, the target concentration may be 5% to 25%. The volume of hydrogen available for injection into the sub-combustion chamber 30 is a function of several features of the decomposed fuel supply, which may include the hydrogen concentration in the pre-combustion fuel supply, and the pressure and temperature of the decomposed fuel supply. The ECU 40 can perform an evaluation of one or more of these features using measurements received from the sensor pack 42. The ECU 40 may be configured to determine the timing and duration of the injectors based on the evaluated features and taking into account the target concentration, which may optionally be 5% to 35%. In certain cases, the target concentration may be between 5% and 25%. In some cases, for example, during engine warm-up, the target concentration may be higher than 35%. For example, when the exhaust is cold, a target hydrogen concentration of over 35% may be used initially to reach the typical engine operating temperature more quickly.

[0209] Referring to Figure 3, an embodiment of a sub-combustion chamber 30 is illustrated in which the interior of the chamber 30 and the orifice 32 are provided with a catalytic coating 48. The catalytic coating 48 is configured to generate some additional hydrogen from ammonia present in either the ammonia / hydrogenated fuel mixture output from the decomposition device 46 and / or from ammonia of the main fuel supply source, which in some configurations may flow from the main combustion chamber 14 into the sub-combustion chamber 30. The catalytic coating 48 may operate to slightly increase the concentration of hydrogen present in the sub-combustion chamber 30 and / or the main combustion chamber 14 at ignition.

[0210] If ammonia is present in the sub-combustion chamber 30 (either when undecomposed ammonia is present in the decomposed fuel, or when ammonia fuel enters the sub-combustion chamber from the main combustion chamber), the catalytic coating 48 illustrated in Figure 3 allows the relatively small amount of ammonia present in the sub-combustion chamber 30 to be partially decomposed into hydrogen and nitrogen, thereby improving overall combustion due to the higher reactivity of hydrogen to ammonia. The conversion rate is temperature-dependent and therefore a function of the engine's operating load and speed. The walls of the sub-combustion chamber 30 and the gas mixture within it will retain some of the heat after the combustion event, which helps to partially chemically decompose the ammonia molecules induced in the main combustion chamber 14 during the intake stroke and the ammonia molecules induced in the sub-combustion chamber 30 during the upward movement of the piston 12 during the compression stroke of the engine cycle. The embodiment of the sub-combustion chamber 30 illustrated in Figure 3 may be used in any of the different embodiments of ammonia fuel engine systems described herein.

[0211] Figure 4 is a flowchart illustrating the operation of an exemplary sequence performed by the ECU40.

[0212] In an example where cylinder 10 is part of an automobile engine, the electronic control device can receive load and speed request information via electronic communication with the automobile's accelerator pedal. The speed and load request information can provide the ECU 40 with the target output of the cylinder and notify it of the amount of main fuel required for combustion to achieve the desired output.

[0213] Cylinder 10 could alternatively be part of a stationary generator engine, a water tank engine, or any other internal combustion engine application, and it would be understood that in those applications, speed and load request information would be provided by components other than the accelerator pedal. For example, in the case of a stationary generator engine, the speed and / or load request could be a user input fed to the ECU 40. In some applications, the ECU 40 could be pre-programmed to operate at a fixed load and speed, or to generate separate power outputs such as low power, medium power, and full power.

[0214] Once engine load and speed requirement information is determined, the electronic control device may evaluate the pressure, temperature, and concentration of hydrogen present in the pre-combustion fuel from one or more sensors associated with the decomposed fuel supply upstream of the pre-combustion fuel injector. For example, a sensor pack 42 illustrated in Figures 1 and 2 may be used. It will be understood that the sensor pack 42 may be located upstream of the pre-combustion fuel injector 34, downstream of the decomposition device 46, or anywhere in the decomposed fuel line between the decomposition device 46 and the pre-combustion fuel injector 34. The determination of hydrogen pressure, temperature, and concentration informs the electronic control device of the amount of hydrogen available for use as pre-combustion fuel.

[0215] Next, the ECU 40 can set the timing and duration of the pre-combustion fuel injector 34. It will be understood that the duration of the pre-combustion fuel injection can be selected by the ECU 40 to inject a desired volume of hydrogen into the sub-combustion chamber 30. The timing of the pre-combustion fuel injector 34 may depend on various parameters, for example, the pressure measured on both sides of the pre-combustion fuel injector.

[0216] In some embodiments, such as when a compressor device is used to increase the decomposed fuel pressure, the decomposed fuel may be supplied at a relatively high pressure, and pre-combustion fuel injection may occur during the compression stroke. In this case, pre-combustion fuel injection may be delayed to reduce the delay between injection and ignition. This may favorably maximize the turbulence (which dissipates over time) present in the pre-combustion fuel chamber to facilitate mixing and enhance combustion efficiency.

[0217] Next, the ECU 40 may set the timing and duration of the main chamber fuel injector 26 to inject a desired volume of ammonia fuel into the main combustion chamber 14. Finally, the ECU 40 may set the appropriate ignition timing.

[0218] It will be understood that the ECU 40 can determine the ignition timing based on predetermined values ​​and act on the ignition device to generate one or more streams of combustion fluid, which, when ignited, release hydrogen-containing decomposed fuel into the main combustion chamber 14 through the orifice 32, smoothly igniting the main ammonia fuel mixture in the main combustion chamber 14. The streams of combustion fluid may include a flame jet. The ECU 40 may also be configured so that, if the hydrogen concentration in the pre-combustion fuel source changes, the amount of main combustion chamber ammonia injection also changes accordingly based on predetermined values ​​of the required load and speed, so that the ratio of total hydrogen to ammonia is maintained within acceptable combustion stability.

[0219] Figures 5-7 illustrate alternative embodiments of the present disclosure in which hydrogen-containing pre-combustion fuel is supplied to a pre-combustion injector 34 from a pre-combustion fuel supply source 36 other than a decomposition device. The pre-combustion fuel supply source 36 may be a hydrogen supply source such as a hydrogen tank. In these embodiments, the pre-combustion injector 34 is supplied with pre-combustion fuel that is not decomposed fuel. In Figures 5-7, the injector 34 may be simply a pre-combustion fuel injector, rather than a “decomposed fuel” injector. The pre-combustion fuel injector 34 is supplied with pre-combustion fuel via a pre-combustion fuel line 44 that connects the pre-combustion fuel injector 34 to the pre-combustion fuel supply source 36.

[0220] Figures 5 and 6 illustrate an ammonia-fueled internal combustion engine system 3 comprising a cylinder 300. Figures 5 and 6 illustrate the same mechanical configuration operating in two different fuel supply scenarios, depending on the pre-combustion fuel pressure in the pre-combustion fuel line 44. The engine system 3 includes a pressure sensor 42 associated with the pre-combustion fuel line 44 and configured to communicate measurements of the pre-combustion fuel pressure to the ECU 40.

[0221] Similar to Figure 1, Figure 5 illustrates a scenario in which the pre-combustion fuel pressure is relatively low (e.g., less than 10 bar) and pre-combustion fuel injection occurs during the intake stroke of cylinder 10, when piston 12 is descending and intake valve 20 is open. In Figure 5, the main fuel injector 26 and the pre-combustion fuel injector 34 are performing fuel injection. That is, both the main fuel containing ammonia and the pre-combustion fuel containing decomposed fuel are sprayed during the intake stroke.

[0222] Figure 6 illustrates an alternative scenario in which the pre-combustion fuel pressure is relatively high (e.g., over 10 bar) and the pre-combustion fuel injection occurs during the compression stroke of cylinder 10, with piston 12 rising and intake valve 20 closed. In this scenario, the main combustion chamber 14 has already received ammonia fuel from the previous intake stroke, and therefore the pre-combustion fuel is injected after the main fuel injection.

[0223] In the scenario illustrated in Figure 6, the ECU 40 receives a reading of the measured pre-combustion fuel pressure upstream of the pre-combustion fuel injector 34, which is approximately 100 bar or higher. In response to this pressure measurement, the ECU 40 activates the pre-combustion fuel injector 34 to initiate the injection of hydrogen-containing pre-combustion fuel at 90°~0° before top dead center (TDC), i.e., during the engine's compression stroke. This method of high-pressure injection of hydrogen-containing fuel into the sub-combustion chamber 30 can result in further improvements in thermodynamic efficiency. The high-pressure injection of hydrogen gas induces a significantly higher level of turbulence in the sub-combustion chamber 30. In addition, the initiation of injection may be delayed during the compression stroke, which means that a high degree of turbulence is maintained at ignition. As a result, the sub-combustion chamber 34 contains a highly turbulent, hydrogen-rich mixture that can be easily ignited thanks to the broad flammability limit of hydrogen. This generates a high-energy flame jet through the orifice 32, which more efficiently burns ammonia in the main combustion chamber 14.

[0224] In either the low-pressure scenario in Figure 5 or the high-pressure scenario in Figure 6, the duration and timing of the main fuel injection and pre-combustion fuel injection are determined by the ECU 40 according to information received from the sensor pack 42, which notifies the ECU 40 of the measured characteristics of the pre-combustion fuel.

[0225] An alternative (not illustrated) control method is to store the hydrogen and nitrogen mixture output from the decomposition device 46 in a pressure vessel with the help of a compressor. Hydrogen can also be separated from nitrogen by methods known in the art.

[0226] Figure 7 illustrates an engine system 4 comprising a cylinder 400 according to an alternative embodiment of the present disclosure. The engine system 4 and cylinder 400 are equivalent to the engine system 3 and cylinder 300 illustrated in Figures 5 and 6, except that, in the case of cylinder 400, the main fuel injector 26 is configured for direct injection into the main combustion chamber 14. Specifically, the main fuel injector 26 is configured as a direct injector located on the cylinder head 24. As discussed above, this can enable precise or more temporally flexible ammonia fuel injection, insofar as ammonia fuel can be injected into the main combustion chamber 14 at any time during the engine cycle, regardless of the position of the intake valve 20. For example, ammonia fuel can be injected into the main combustion chamber 14 during the compression stroke of the engine system 4 when the intake valve 20 is in the closed position.

[0227] It will be understood that pre-combustion chamber injection can occur at either low or high pressure, depending on other parameters of the engine system and as described above. Ammonia fuel injection provided by the main fuel injector 26 can occur during the intake stroke when the intake valve 20 is open, as illustrated in Figures 1 and 5. Alternatively, the main fuel injection provided by the ammonia fuel injector 26 can occur during the cylinder compression stroke when the intake valve 20 is closed (the position illustrated in Figures 2 and 7). Figures 2 and 7 illustrate ammonia fuel and decomposed fuel being injected during the upward movement of the piston 12 and during the compression stroke of the engine systems 2 and 4. Figures 8-11 illustrate decomposed fuel being injected into the pre-combustion chamber and the main combustion chamber via the pre-combustion chamber during the upward movement of the piston 12 and during the compression stroke of the engine system.

[0228] In some embodiments, the ECU 40 may inject ammonia fuel during both the intake and compression strokes. For example, injection of ammonia main fuel may begin during the intake stroke and continue until it stops while the cylinder 200 is undergoing the compression stroke. In certain embodiments of the present disclosure, the main fuel injection provided by the main fuel injector 26 may be configured as a split injection. A split injection may consist of two injection events: a first injection event is a separate injection of main fuel during the intake stroke, and a second injection event is a separate injection of main fuel during the compression stroke.

[0229] In certain embodiments, the split injection of ammonia includes a first injection occurring immediately before the combustion fluid stream from the sub-combustion chamber 30 enters the main chamber 14, and a second injection occurring after the ammonia fuel from the first injection has been substantially burned by the combustion fluid stream in the main chamber 14. It should be understood that any of the embodiments described herein may be configured in the split injection mode discussed above.

[0230] In another embodiment, all of the ammonia fuel in the main fuel injection is injected just before the combustion fluid stream from the sub-combustion chamber 30 enters the main chamber 14. In yet another embodiment, the start of the main fuel injection is initiated just before the combustion fluid stream enters the main chamber 14, such that a portion of the main fuel injection period overlaps with the adsorption period of the combustion fluid stream. All of these embodiments are thought to enable rapid and rapid combustion and a reduction in ammonia slip through the exhaust port.

[0231] Referring to Figure 8, an internal combustion engine system 5 comprising a cylinder 500 is illustrated according to an alternative embodiment of the present disclosure. The cylinder 500 is configured as a two-stroke engine cylinder, comprising a piston 12, an intake port comprising an intake port pair 160, an exhaust port comprising an exhaust port pair 18 that can be selectively closed by an exhaust valve 22, a main combustion chamber 14, and a sub-combustion chamber 30 that is in fluid communication with the main combustion chamber 30 via a plurality of orifices 32. A fuel inlet comprising a decomposed fuel injector 34 is provided in the sub-combustion chamber 30.

[0232] The engine system 5 includes a cracking device 46 connected to an ammonia fuel source having an ammonia fuel tank 28. The cracking device is configured to produce a partially cracked fuel containing a mixture of hydrogen, uncracked ammonia, and nitrogen, according to a target concentration of hydrogen relative to the total amount of hydrogen and ammonia present in the cracked fuel. In certain embodiments, the cracking device 46 may be configured to produce a partially cracked fuel containing 5% to 35% hydrogen relative to the volume of ammonia.

[0233] The decomposed fuel is delivered to a decomposed fuel injector 34 via a decomposed fuel line 44. The decomposed fuel injector 34 is configured to inject a spray 50 of the decomposed fuel into a pre-combustion chamber 30. The decomposed fuel line 44 is provided with a sensor 42 that communicates with an electronically controlled device comprising an ECU 40. The ECU 40 is configured to use measurements received from the sensor 42 to evaluate the characteristics of the hydrogen present in the decomposed fuel. The ECU 40 communicates with and controls the operation of the decomposed fuel injector 40. The ECU 40 is configured to control the introduction of the partially decomposed fuel into the pre-combustion chamber 30 according to the evaluated characteristics of the hydrogen. The pre-combustion chamber 30 is also provided with an ignition device comprising a spark plug 38 that communicates with and is controlled by the ECU 40.

[0234] Cylinder 500 is configured such that a decomposed fuel injector 34 allows for the introduction of partially decomposed fuel into a sub-combustion chamber and into the main combustion chamber via an orifice 32. The flow of decomposed fuel through the orifice 32 into the main combustion chamber 14 forms a spray 52 that supplies decomposed fuel to the main combustion chamber 14. Thus, both the fuel spray 50 into the sub-combustion chamber and the fuel spray 52 into the main combustion chamber contain decomposed fuel. As a result, the decomposed fuel present in the main combustion chamber 14 and the decomposed fuel present in the sub-combustion chamber 30 are supplied from the same fuel inlet, which is equipped with a decomposed fuel injector 34. The decomposed fuel present in the sub-combustion chamber 30 is supplied directly by the decomposed fuel injector 34. The decomposed fuel present in the main combustion chamber 14 is supplied indirectly by the decomposed fuel injector 34, insofar as it is supplied via the sub-combustion chamber 30. As a result, the fuel present in the main combustion chamber 14 and the fuel present in the sub-combustion chamber 30 are supplied from the same fuel inlet, which includes an ammonia fuel tank 28. As can be seen, such an arrangement avoids the need for two or more separate fuel sources. In some cases, only a single fuel source (e.g., an ammonia source) may be used.

[0235] The ECU 40 is configured to supply a sufficient amount of partially decomposed fuel to the sub-combustion chamber 30 and the main combustion chamber 14 to fuel operationally sufficient combustion in the main combustion chamber 14. Upon supplying fuel to the main combustion chamber 14 and the sub-combustion chamber 30, the ECU 40 activates the spark plug 40 to enable ignition of the decomposed fuel present in the sub-combustion chamber. The combustion stream of fuel, which may include a flame jet, enters the main combustion chamber 14 through the orifice 32, causing or facilitating ignition of the decomposed fuel present in the main combustion chamber 14.

[0236] The ECU 40 may be configured to control the injection timing or duration of the partially decomposed fuel spray 50 into the sub-combustion chamber according to evaluated characteristics of the decomposed fuel, such as the decomposed fuel temperature and / or decomposed fuel pressure and / or decomposed fuel gas composition.

[0237] In this configuration, the cylinder 500 is configured to supply fuel to both the pre-combustion chamber 30 and the main combustion chamber 14 using a single fuel inlet (a decomposed fuel injector 34). This configuration is advantageous as long as a second fuel inlet, exclusively associated with the main combustion chamber 14, is not required. Furthermore, this configuration allows for the provision of a two-stroke engine with a pre-combustion chamber 30 to enhance engine efficiency. The use of a single decomposed fuel injector 30 for introducing partially decomposed fuel is also advantageous for volumetric considerations when the cylinder head does not have enough space to accommodate a separate main combustion chamber injector.

[0238] Referring to Figure 9, a two-stroke internal combustion engine system 6 is illustrated, comprising a cylinder 600 having a similar configuration to cylinder 500, but further comprising an ammonia fuel injector 26 configured to introduce ammonia fuel into a pre-combustion chamber 30. The ammonia fuel injector 26 is supplied with ammonia fuel from an ammonia fuel tank 28, which supplies a cracking device 46 that supplies cracked fuel to a cracked fuel injector 34. Thus, both the cracked fuel injector 34 and the ammonia fuel injector 30 can be supplied from a single ammonia fuel tank 28.

[0239] Both the ammonia fuel injector 30 and the decomposed fuel injector 34 are positioned at the head of the sub-combustion chamber 30. In the illustrated embodiment, the ammonia fuel injector 30 and the decomposed fuel injector 34 may each be configured for direct injection into the sub-combustion chamber 30. Alternatively, the two injectors 26, 34 may introduce fuel into a port or line that is in fluid communication with the sub-combustion chamber, and this introduction occurs upstream of the sub-combustion chamber.

[0240] The ammonia fuel injector 26 is configured to introduce ammonia fuel into the main combustion chamber via a sub-combustion chamber. The ammonia fuel injector can deliver a sufficient amount of ammonia fuel to the sub-combustion chamber, which is then discharged from the sub-combustion chamber 30 through the orifice 32. In this way, the main combustion chamber 14 can be fueled by ammonia fuel 14 from the ammonia fuel injector 30. Next, the decomposed fuel injector 34 injects hydrogen-containing decomposed fuel into the sub-combustion chamber 30. The highly reactive decomposed fuel, upon ignition by the spark plug 38, generates a stream of combustion fluid entering the main combustion chamber 14, causing or promoting the ignition and combustion of the less reactive ammonia fuel present in the main combustion chamber 14.

[0241] In the embodiment illustrated in Figure 9, the sensor 42 is not directly associated with the decomposed fuel (as in the case of engine system 5 described above), but instead is associated with the decomposition device 46. Specifically, the sensor 42 of engine system 6 comprises a temperature sensor 42 associated with the decomposition device 46.

[0242] Referring further to the engine system 6 in Figure 9, the spark plug 38, ammonia fuel injector 26, and decomposed fuel injector 34 are electronically controlled by the ECU 40. The ECU communicates with a sensor comprising a temperature sensor 42 associated with the decomposition device 46. The ECU 40 is configured to use temperature measurements received from the temperature sensor 42 to evaluate the characteristics of hydrogen in the decomposed fuel. The ECU 40 is provided with predetermined performance information of the decomposition device as a function of the temperature of the decomposition device. The ECU 40 receives real-time temperature measurements of the decomposition device, obtains estimated performance characteristics of the decomposition device based on the measured temperature, and evaluates one or more characteristics of the decomposed fuel. For example, the ECU 40 may use temperature measurements of the decomposition device received from the temperature sensor 42 to evaluate one or more of the hydrogen concentration, pressure, or temperature of the decomposed fuel.

[0243] The ECU 40 is configured to control the introduction of the decomposed fuel into the sub-combustion chamber 30 and the introduction of the ammonia fuel into the sub-combustion chamber 30 according to the evaluated hydrogen characteristics. For example, the ECU 40 can determine the injection timing and duration of the ammonia fuel injector 26 and the decomposed fuel injector 34 according to the evaluated hydrogen characteristics.

[0244] The engine system 6 includes a compressor device 43 configured to increase the pressure of the decomposed fuel supplied to the decomposed fuel injector 34. The compressor device 43 may be positioned in the decomposed fuel line 44, downstream of the decomposition device 46 and upstream of the decomposed fuel injector 34. The compressor device may be configured to compress the decomposed fuel from a relatively low pressure (about 10 bar or less) at the output of the decomposition device 46 to a higher pressure. In some embodiments, the higher pressure supplied by the compressor device may be up to 100 bar. In some embodiments, the compressor device 43 is electronically controlled by an ECU 40. In some embodiments, the compressor device 43 may be a variable pressure compressor device, and the ECU may selectively adjust the decomposed fuel pressure supplied to the decomposed fuel injector 34.

[0245] It will be understood that the use of the compressor device 43 can, to its advantage, allow for the injection of decomposed fuel according to the high-pressure scenario discussed above with reference to Figure 6. For example, high-pressure injection of decomposed fuel can induce a significantly higher level of turbulence in the sub-combustion chamber 30. In addition, the start of injection may be delayed during the compression stroke, which means that a high degree of turbulence is maintained at ignition. As a result, the sub-combustion chamber 34 contains a highly turbulent hydrogen-containing mixture that can be easily ignited thanks to the broad flammability limit of hydrogen. This can generate a stream of high-energy combustion fluid through the orifice 32, causing the fuel to burn more efficiently in the main combustion chamber 14.

[0246] Referring further to Figure 9, it is shown that a spray of ammonia fuel 56 is being injected into the sub-combustion chamber 30. Simultaneously, it is shown that a spray of ammonia fuel 58 is being injected from the sub-combustion chamber into the main combustion chamber 14 via the orifice 32. This occurs during the compression stroke of the engine system 6, as indicated by the directional arrow on the piston 12.

[0247] In some embodiments, a controllable high-pressure pump device may also be provided upstream of the ammonia fuel injector 26 to achieve a desired ammonia fuel pressure. This may be particularly useful when ammonia is injected in a liquid state to carry out injection during the engine's compression stroke.

[0248] Referring to Figure 10, a further embodiment is illustrated in which the two-stroke engine system 7 includes a cylinder 700 having a configuration similar to that of cylinder 500 in Figure 8, wherein cylinder 700 is equipped with a single decomposed fuel injector 34 configured to introduce decomposed fuel into both the pre-combustion chamber 30 and the main combustion chamber 14. Cylinder 600 differs from cylinder 500 in that the ECU 40 communicates with a controllable electric heating device 54 configured to heat the decomposition device 46. Thus, the ECU 40 can adjust the performance of the decomposition device 46 by controlling the heating device 54, and therefore adjust the composition of the decomposed gas produced by the decomposition device 46. The heating device 54 can favorably maintain sufficient decomposition performance and hydrogen production at low engine temperatures and, for example, for engine starting. The controllable heating device 54 may be used in conjunction with the decomposition device 46 in any of the embodiments described above. The use of a controllable heating device may be advantageous in any embodiment of this disclosure where engine exhaust heat is insufficient to achieve sufficient decomposition performance.

[0249] The engine system 7 in Figure 10 has a sensor arrangement that includes a disassembly device temperature sensor 42a and a fuel sensor 42b, both of which communicate with the electronic control unit 40. The disassembly device temperature sensor 42a may be configured to provide temperature information related to the disassembly device 46 to the ECU 40. The fuel sensor 42b may be configured to provide fuel information, including fuel temperature and pressure, to the ECU 40.

[0250] As mentioned above, engine system 5 in Figure 8 and engine system 7 in Figure 10 are provided with a single fuel injector equipped with a decomposed fuel injector 34. This is in contrast to engine systems 1, 2, 3, and 4 in Figures 1, 2, 5, 6, and 7, which are provided with a decomposed fuel injector and a separate ammonia fuel injector. In these embodiments, the hydrogen-containing decomposed fuel introduced by the decomposed fuel injector can be diluted by the operation of the ammonia fuel injector. These engine systems may be configured to introduce the decomposed fuel and ammonia into the cylinder to achieve a hydrogen fuel concentration of 5% to 35%.

[0251] In contrast, the “single-injector” engine systems 5 and 7 illustrated in Figure 8 are configured such that the fuel mixture introduced into and ignited in the cylinder is the same compositional mixture produced by the decomposition device. Therefore, the decomposition device 46 in these embodiments may be configured to produce decomposed fuel having a hydrogen concentration within a target range. For example, the decomposition device may be configured to produce decomposed fuel having a hydrogen concentration between 5% and 35%. As discussed above, this concentration may typically be suitable for regular and sustained engine operation. Higher hydrogen concentrations may be selected as needed during certain conditions, such as cold starts and at low ambient temperatures.

[0252] Examples of decomposition device control, as discussed above, may include controlling the amount of exhaust gas supplied to the decomposition device. For example, if the temperature of the decomposition device (and therefore the decomposition efficiency) approaches or exceeds a desired limit, such as when the hydrogen concentration approaches or exceeds a desired limit, exhaust heat may be bypassed from the decomposition device. The operation of exhaust gas bypass may be controlled by an electronically controlled device. Another example is through the control of a controllable heating device, as illustrated in Figure 10 by heating device 54.

[0253] The electronic control device may be configured to selectively reduce heat to the decomposition device by temporarily removing a heat source from the decomposition device (such as by bypassing exhaust gases or turning off or weakening the electronic heating device) when it is desirable to reduce the hydrogen concentration. As mentioned, this may be particularly desirable when a single fuel injector is used. In embodiments in which a separate ammonia fuel injector is used, the decomposition device may operate at maximum decomposition efficiency, and the hydrogen concentration may be diluted to a target range in the cylinder by introducing ammonia fuel through the ammonia fuel injector.

[0254] Figure 11 illustrates an alternative embodiment of the present disclosure in which the two-stroke engine system 8 comprises a cylinder 800. Similar to some previous embodiments, the engine system 8 comprises a main combustion chamber 14, a sub-combustion chamber 30 communicating with the main combustion chamber via a plurality of orifices 32, an ECU 40, a fuel injector 34 controlled by the ECU 40, and a spark plug 38 controlled by the ECU 40. The fuel injector 34 is configured to inject fuel directly into the sub-combustion chamber 34 and also to supply fuel to the main combustion chamber 14 via the fuel supply of the sub-combustion chamber 30. As shown in the figure, a spray of fuel 56 is injected from the fuel injector 34 into the sub-combustion chamber. This causes a spray of the same fuel 58 to enter the main combustion chamber 14 via the orifice 32. The fuel injector 34 is supplied with fuel from a fuel line 44 that receives fuel from a fuel supply source 28. In the illustrated embodiments, the fuel source contains ammonia fuel 28, but it will be understood that other fuel types such as gasoline, diesel, methane, LPG, hydrogen-containing fuel mixtures may be used, or may be separately blended or mixed to improve the flammability of the ammonia.

[0255] The embodiment shown in Figure 11 differs from the previously described embodiment in that it does not involve the use of hydrogen-containing fuel or a fuel sensor that communicates measurements to the ECU 40. Figure 11 illustrates that an advantageous fuel supply system, in which the main combustion chamber 14 is supplied with fuel through the sub-combustion chamber 30, may be used in an engine that is not necessarily limited to hydrogen-containing fuel, but may or may not be configured to control fuel delivery along with other fuel types, and based on an evaluation of the hydrogen characteristics of the fuel.

[0256] In an alternative embodiment, the engine system 8 in Figure 11 is equipped with a pressure sensor and / or temperature sensor in the fuel line 44 to inform the ECU 40 of the fuel temperature and / or pressure upstream of the fuel injector 34. The ECU can control fuel injection according to the temperature and / or pressure measurements provided by the sensors.

[0257] The embodiment illustrated in Figure 11 illustrates a situation in which a conventional two-stroke engine is modified to include a sub-combustion chamber 30 by forming an inlet hole in the cylinder head and installing the sub-combustion chamber 30 in the newly formed inlet hole. It will be understood that any of the embodiments illustrated and described herein can be achieved by modifying a conventional internal combustion engine to include a sub-combustion chamber, and this conversion is not necessarily limited to a two-stroke internal combustion engine.

[0258] Another example (not shown) of converting an engine to include a sub-combustion chamber is the conversion of a hydrocarbon engine (e.g., a diesel engine) that already includes a fuel inlet communicating with the main combustion chamber. In this case, the fuel inlet of the sub-combustion chamber may be cut off, and the downstream end of the sub-combustion chamber 30 may be connected in place of the fuel inlet, so that the sub-combustion chamber communicates with the main combustion chamber 14. The fuel source may then be connected to the upstream end of the sub-combustion chamber. This type of engine conversion is not dependent on a spark plug and is therefore particularly suitable for compression-ignition engines that typically have sufficient space in the cylinder head to accommodate an aftermarket sub-combustion chamber.

[0259] As discussed above, embodiments of the present disclosure in which the main combustion chamber is fueled through a secondary combustion chamber may be particularly beneficial in two-stroke engines in which the main combustion chamber is typically fueled through an intake port, which presents a high risk of fuel leaking from the cylinder through the exhaust valve / port during the scavenging process. By introducing fuel into the main combustion chamber through the secondary combustion chamber and timing the injection after the closure of the exhaust valve / port, fuel slip can be advantageously reduced or eliminated.

[0260] Referring to Figures 12–16, several exemplary engine injection and ignition timing diagrams are provided for various embodiments of engine systems according to this disclosure. In each of these figures, the following acronyms are used: EVO: Exhaust valve open, IPO: Inlet port open, IPC: Inlet port closed, EVC: Exhaust valve closed, TDC: Top dead center, BDC: Bottom dead center.

[0261] Figure 12 relates to an embodiment in which a single fuel injector is used and which may relate to embodiments illustrated, for example, in Figures 8, 10, and 11. As can be seen from Figure 12, fuel is injected substantially into the pre-combustion chamber after the exhaust valve has closed and is substantially completed before ignition. The period from the end of injection to ignition allows the fuel to mix well with air and fresh air in the main chamber, and as the piston moves toward TDC, some of the air-fuel mixture is pushed back into the pre-combustion chamber, creating an ignitable mixture in the pre-combustion chamber as a whole.

[0262] The timing system illustrated in Figure 12 may be used in the embodiment illustrated in Figure 11, which primarily uses ammonia fuel. For example, the ammonia fuel may be either liquid or gaseous, and a high-energy spark ignition system with one or two spark plugs may be used to enhance flammability. The timing system illustrated in Figure 12 may also be used when partially decomposed ammonia gas containing hydrogen is introduced into both the pre-combustion chamber and the main combustion chamber via a single injector, as in the embodiments illustrated in Figures 8 and 10.

[0263] Figures 13 to 16 are examples of potential injection and ignition timings of an embodiment of the present disclosure having two injectors in the sub-combustion chamber, as shown in FIG. 9. Each figure shows labeled time sequences 1 to 4 corresponding to actions defined below for each figure.

[0264] Figure 13: 1. Primary fuel injection window, 2. Secondary fuel injection window, 3. Ignition window

[0265] Figure 14: 1. Primary fuel injection window, 2. First secondary fuel injection window, 3. Second secondary fuel injection window, 4. Ignition window

[0266] Figure 15: 1. Secondary fuel injection window, 2. Ignition window, 3. Primary fuel injection window

[0267] Figure 16: 1. First secondary fuel injection window, 2. Second secondary fuel injection window, 3. Ignition window, 4. Primary fuel injection window

[0268] In the above examples, "primary fuel" relates to the main fuel introduced into the main combustion chamber, and "secondary fuel" is understood to be the fuel introduced into the sub-combustion chamber for the purpose of being ignited therein to promote or complement the combustion of the primary fuel in the main combustion chamber. In some embodiments, the primary fuel can be ammonia fuel, and the secondary fuel can be a hydrogen-containing fuel such as decomposed fuel (or otherwise partially decomposed fuel) provided from a decomposition device. In some alternative examples, the secondary fuel can be hydrogen provided by a hydrogen tank.

[0269] It will be understood that various injection strategies can be implemented for both pre-combustion fuel injectors and main fuel injectors, depending on the injection pressure. In some cases, as shown in Figures 14, 15, and 16, higher injection pressures may improve combustion by performing a late injection during the compression stroke. For example, if a pressurized hydrogen supply is used as a pre-combustion fuel, split injection may be implemented such that the first injection is performed during the intake stroke or initial compression stroke when the piston is near the BDC or after the exhaust valve has closed, in the case of a two-stroke engine, and the second late injection is performed during the compression stroke. Thus, the first injection may bring some hydrogen into the main chamber, which improves flammability when the ammonia in the main chamber ignites, and the second late injection will bring higher turbulence and concentration of hydrogen into the sub-chamber, which will significantly increase the enthalpy of the flame jet, and consequently result in a faster and more complete combustion of the ammonia in the main chamber.

[0270] In some embodiments, maintaining a choke flow would be advantageous for better injection mass control and repeatability. In most scenarios, a choke flow is expected to be achieved when the pressure upstream of the injector is at least twice the pressure in the sub-combustion chamber throughout the entire duration of injection. The main fuel (e.g., ammonia fuel) can be injected during the intake stroke or initial compression stroke when low injection pressures are used. In some embodiments, the ammonia fuel may be pressurized into a liquid state, or used as a compressed gas or supercritical fluid.

[0271] In yet another example, as shown in Figures 15 and 16, ammonia can also be burned in a mixed-control combustion mode, where the hydrogen-containing fuel is first injected and ignited relatively late in the compression stroke, and then, as soon as the combustion fluid stream enters the main combustion chamber, the ammonia fuel is injected, enters behind the flame jet in the main combustion chamber, and ignited. This timing mode is advantageous because, at ignition, it can result in a substantially higher concentration of hydrogen present in the sub-combustion chamber than the hydrogen concentration in the main combustion chamber.

[0272] It should be noted that the injection windows shown in the examples in Figures 12-16 should not be misunderstood as injection duration, but rather as the period during which actual injection is performed. It should also be noted that the injection windows shown in the examples in Figures 12-16 are not limited to a two-stroke engine cycle, but can be implemented in a four-stroke engine cycle as well.

[0273] Figures 17–23 provide various fuel schematics in which the decomposed fuel is supplied to the pre-combustion chamber fuel injector (PCC injector) at various exemplary pressures and temperatures. Figures 17–21 also illustrate preferred ammonia decomposition processes that may be carried out by a decomposition device as part of the engine according to this disclosure.

[0274] As shown in each of the examples in Figures 17–21, ammonia moves from the ammonia fuel tank through the evaporator section of a reheater / evaporator device where the ammonia fuel receives heat. The ammonia fuel then moves to an exhaust heat exchanger (HX) and a decomposition device, which is supplied with heat from the engine exhaust and produces decomposed ammonia containing a mixture of hydrogen, nitrogen, and possibly undecomposed ammonia. The mixture then passes through the reheater section of the reheater / evaporator device, where it is cooled and transfers heat to the ammonia passing through the evaporator section of the reheater / evaporator device. The cooled mixture then passes through a compressor to increase the pressure of the decomposed fuel before flowing into the PCC injector. Figures 17–21 provide various examples of how this general process may be configured to provide decomposed fuel at different temperatures and pressures to the PCC injector.

[0275] The use of catalytic decomposition equipment can be particularly advantageous compared to decomposed ammonia in a non-catalytic form. While ammonia can be decomposed without a catalyst, it will be understood that catalytic decomposition lowers the temperature required for decomposition and allows for decomposition at higher pressures. This can advantageously allow for a larger-scale utilization of engine waste heat from the exhaust, intercooler, and coolant to evaporate and heat the liquid ammonia supply and supply the thermal energy required for chemical decomposition, thereby effectively increasing the overall efficiency of the engine. Decomposition at higher pressures is advantageous in that it allows for higher feed pressures for liquid ammonia, thereby reducing the need to compress the decomposed ammonia.

[0276] References herein to “upward” or “downward” movement of the piston within a cylinder will be understood with reference to illustrated embodiments in which the cylinder is shown perpendicular to the cylinder head positioned above the main combustion chamber. It will be understood that the internal combustion cylinder does not necessarily have to be perpendicular. Accordingly, references herein to “upward” movement of the piston will be understood to mean movement toward the cylinder head (and decreasing the internal volume of the main combustion chamber), and references herein to “downward” movement of the piston will be understood to mean movement away from the cylinder head (and increasing the internal volume of the main combustion chamber).

[0277] In this specification, the term “sub-combustion chamber” will be understood to mean an enclosed volume that communicates with the main combustion chamber via one or more orifices, etc., allowing gases from the sub-combustion chamber to burn and enter the main combustion chamber, thereby facilitating the combustion of fuel present in the main combustion chamber. The sub-combustion chamber is not limited to any particular shape, volume, or configuration, and these parameters may vary depending on the specific application of the engine system. For example, in some cases, different sub-combustion chambers may have different orifices or be formed in a different manner with respect to the ignition device, but still provide an enclosed volume that is in fluid communication with the main chamber and configured to allow combustion fluids to move into (e.g., eject) the main chamber to facilitate / assist combustion in that chamber. Those skilled in the art will be able to readily implement various embodiments accordingly.

[0278] Finally, while the embodiments illustrated herein relate to internal combustion engines having pistons, it will be understood that engines according to this disclosure may be pistonless engines, such as rotary engines, which do not have pistons. In this regard, references to “cylinder” herein will be understood to encompass both conventional reciprocating internal combustion engine cylinders that house pistons, and rotary engine cylinder housings that generally include a rotor that rotates within the cylinder housing. A well-known example of a rotary engine is the Wankel engine.

[0279] Those skilled in the art will understand that the disclosure described herein is subject to variations and modifications other than those specifically described. It is understood that this disclosure includes all such variations and modifications that fall within the intent and scope of this disclosure.

[0280] In this specification (including the claims), where the terms “comprise,” “comprises,” “comprised,” or “comprising” are used, they should be construed as specifying the presence of the described feature, element, step, or component, but not as excluding the presence of one or more other features, elements, steps, or components.

Claims

1. An ammonia fuel internal combustion engine system, A decomposition device, which is connectable to an ammonia fuel supply source and configured to produce a decomposed fuel containing a mixture of nitrogen and hydrogen by decomposing the ammonia fuel supplied by the ammonia fuel supply source during the operation of the engine, - A main combustion chamber, and an intake port and an exhaust port, respectively, that are in fluid communication with the main combustion chamber. - A sub-combustion chamber having fluid communication with the main combustion chamber via at least one orifice, further comprising a decomposed fuel inlet for enabling the introduction of the decomposed fuel supplied from the decomposition device into the sub-combustion chamber, - An ignition device operably positioned together with the sub-combustion chamber and configured to ignite the decomposed fuel in the sub-combustion chamber, wherein the sub-combustion chamber and / or the orifice are configured to generate a stream of combustion fluid from the sub-combustion chamber to the main combustion chamber via the orifice when the decomposed fuel is ignited in the sub-combustion chamber, in order to enable ignition of the fuel present in the main combustion chamber; - A sensor arrangement configured to measure the characteristics of the decomposed fuel, An ammonia fuel internal combustion engine system comprising: an electronic control device that communicates with the sensor arrangement and the ignition device, configured to evaluate the characteristics of the hydrogen present in the decomposed fuel using measurements received from the sensor arrangement, and to control the introduction of the decomposed fuel into the sub-combustion chamber according to the evaluated characteristics of the hydrogen.

2. The ammonia fuel internal combustion engine system according to claim 1, wherein the sensor arrangement and the electronic control device are configured to evaluate the hydrogen concentration in the decomposed fuel.

3. The ammonia fuel internal combustion engine system according to any one of the prior claims, wherein the sensor arrangement is configured to measure the pressure and temperature of hydrogen present in the decomposed fuel.

4. The ammonia fuel internal combustion engine system according to any one of the prior claims, wherein the sensor arrangement is configured to measure the properties of the decomposed fuel, obtained directly from the decomposed fuel.

5. The ammonia fuel internal combustion engine system according to any one of the prior claims, wherein the sensor arrangement is configured to measure the characteristics of the decomposed fuel obtained indirectly with respect to the decomposed fuel.

6. An ammonia fuel internal combustion engine system according to any one of the prior claims, comprising an electrical conductivity sensor configured such that the sensor arrangement enables the electronic control device to evaluate the hydrogen concentration in the decomposed fuel.

7. The ammonia fuel internal combustion engine system according to claim 4 or 5, wherein the sensor arrangement comprises a decomposed fuel pressure sensor and a decomposed fuel temperature sensor located in the flow path of the decomposed fuel.

8. The ammonia fuel internal combustion engine system according to any one of the prior claims, wherein the sensor arrangement comprises a decomposition device temperature sensor configured to measure the temperature of the decomposition device, and the electronic control device is configured to evaluate the characteristics of the hydrogen present in the decomposed fuel using the decomposition device temperature measurement value received from the decomposition device temperature sensor.

9. The ammonia fuel internal combustion engine system according to any one of the prior claims, wherein the electronic control device is configured to control the duration and / or timing of the introduction of the decomposed fuel into the sub-combustion chamber.

10. The ammonia fuel internal combustion engine system according to any one of the prior claims, wherein the electronic control device is configured to control the amount of hydrogen present in the sub-combustion chamber by controlling the amount of decomposed fuel introduced into the sub-combustion chamber.

11. The ammonia fuel internal combustion engine system according to any one of the prior claims, wherein the electronic control device is configured to adjust the composition of the decomposed fuel introduced into the sub-combustion chamber.

12. The ammonia fuel internal combustion engine system according to claim 11, wherein the electronic control device is configured to control the operation of the decomposition device so as to adjust the concentration of hydrogen present in the decomposed fuel.

13. The ammonia fuel internal combustion engine system according to claim 11 or 12, further comprising a controllable heating device configured to heat the decomposition device, wherein the heating device communicates with the electronic control device.

14. The ammonia fuel internal combustion engine system according to any one of claims 11 to 14, wherein the electronic control device controls the operation of the decomposition device according to a target hydrogen concentration of 5 volume% to 35 volume%.

15. An ammonia fuel internal combustion engine system according to any one of the prior claims, wherein the fuel present in the main combustion chamber is decomposed fuel produced by the decomposition device and introduced into the main combustion chamber via the sub-combustion chamber and the orifice.

16. The ammonia fuel internal combustion engine system according to claim 15, wherein the electronic control device is configured to control the introduction of the decomposed fuel into the main combustion chamber by controlling the timing and / or duration of the introduction of the decomposed fuel into the sub-combustion chamber during operation.

17. An ammonia fuel internal combustion engine system according to any one of the prior claims, further comprising an ammonia fuel inlet configured to introduce ammonia fuel into the main combustion chamber, wherein the fuel present in the main combustion chamber includes ammonia fuel introduced by the ammonia fuel inlet.

18. The ammonia fuel internal combustion engine system according to claim 17, wherein the ammonia fuel inlet is configured to introduce ammonia fuel into the main combustion chamber via the sub-combustion chamber and the orifice, and the ammonia fuel inlet is positioned in the sub-combustion chamber.

19. The ammonia fuel internal combustion engine system according to claim 17 or 18, wherein the ammonia fuel inlet comprises an ammonia fuel injector, and the ammonia fuel injector communicates with and is controlled by the electronic control device.

20. The ammonia fuel internal combustion engine system according to claim 19, wherein the electronic control device is configured to control the duration and timing of the introduction of ammonia fuel into the sub-combustion chamber by controlling the operation of the ammonia fuel injector.

21. The ammonia fuel internal combustion engine system according to claim 20, wherein the electronic control device is configured to control the introduction of ammonia into the main combustion chamber by controlling the duration and timing of the introduction of ammonia fuel into the sub-combustion chamber.

22. The ammonia fuel internal combustion engine system according to any one of claims 17 to 21, wherein the electronic control device determines the volume of ammonia to be introduced into the main combustion chamber according to the electronic control device's evaluation of the amount of hydrogen present in the decomposed fuel.

23. The ammonia fuel internal combustion engine system according to any one of claims 17 to 22, wherein the electronic control device is configured to control the introduction of ammonia fuel into the main combustion chamber and the introduction of decomposed fuel into the sub-combustion chamber according to a target hydrogen concentration.

24. The ammonia fuel internal combustion engine system according to claim 23, wherein the target hydrogen concentration is 5% by volume to 35% by volume.

25. The inlet of the decomposed fuel is equipped with a decomposed fuel injector that communicates with and is controlled by the electronic control device, and for each engine cycle, the electronic control device performs the following sequence of actions: - Determine the engine operation requirements. - To evaluate the pressure and temperature of the hydrogen in the decomposed fuel generated by the decomposition device via the sensor arrangement. - Setting the timing and duration of the fuel injector for the disassembled fuel. - Setting the timing and duration of the ammonia fuel injector, - An ammonia fuel internal combustion engine system according to any one of claims 19 to 24, which is responsible for setting the ignition timing of the ignition device.

26. The ammonia fuel internal combustion engine system according to claim 25, wherein the engine operation request is an engine load request and / or an engine speed request.

27. The ammonia fuel internal combustion engine system according to any one of the prior claims, wherein the decomposition device is in thermal communication with the waste heat generated by the engine.

28. An ammonia-fueled internal combustion engine system according to any one of the prior claims, wherein the sub-combustion chamber includes a coating of a catalytic material configured to partially convert ammonia introduced into the cylinder into hydrogen, the catalytic material being coated on the inner wall of the sub-combustion chamber and / or on the surface of the at least one orifice.

29. The ammonia fuel internal combustion engine system according to any one of the prior claims, wherein at least one orifice has a diameter of 0.8 mm to 3.0 mm.

30. An ammonia-fueled internal combustion engine system according to any one of the prior claims, wherein the sub-combustion chamber is in fluid communication with the main combustion chamber via a plurality of orifices configured to generate a plurality of combustion fluid streams flowing into the main combustion chamber.

31. The ammonia fuel internal combustion engine system according to any one of the prior claims, wherein the volume of the sub-combustion chamber is at least 3% of the gap volume of the cylinder.

32. An ammonia fuel internal combustion engine system according to any one of the prior claims, wherein the decomposed fuel produced by the decomposition device is supplied to the decomposed fuel inlet without undergoing a separation process.

33. An ammonia fuel internal combustion engine system according to any one of the prior claims, further comprising a compressor device configured to compress the decomposed fuel upstream of the sub-combustion chamber.

34. The ammonia-fueled internal combustion engine system according to claim 35, wherein the inlet for the decomposed fuel comprises a decomposed fuel injector, and the compressor device is configured to compress the decomposed fuel to a pressure that allows for a choke flow across the decomposed fuel injector.

35. A method for operating an ammonia-fueled internal combustion engine, which has a sub-combustion chamber in fluid communication with a main combustion chamber, wherein the method is - Operate a cracking device supplied with ammonia fuel to produce a cracked fuel containing a mixture of hydrogen and nitrogen, - Introducing fuel into the main combustion chamber, - Introducing the decomposed fuel from the decomposition device into the sub-combustion chamber, - Ignition of the decomposed fuel in the sub-combustion chamber to generate a stream of combustion gas entering the main combustion chamber from the sub-combustion chamber, thereby igniting the fuel present in the main combustion chamber, A method comprising: controlling the introduction of the decomposed fuel into the sub-combustion chamber using information received from a sensor arrangement associated with the decomposed fuel.

36. The method according to claim 35, wherein the fuel introduced into the main combustion chamber includes the decomposed fuel from the decomposition device.

37. The method according to claim 35 or 36, wherein the fuel introduced into the main combustion chamber includes ammonia fuel from an ammonia fuel supply source.

38. The method according to any one of claims 35 to 37, wherein the sensor arrangement comprises a pressure sensor, and the method includes receiving an indication from the pressure sensor of the decomposed fuel pressure being supplied to the fuel inlet.

39. The method according to claim 38, wherein if the indicated pressure of the decomposed fuel supplied to the fuel inlet is less than 10 bar, the method comprises initiating the introduction of the decomposed fuel into the sub-combustion chamber during the intake stroke of the cylinder.

40. The method according to claim 38 or 39, wherein if the indicated pressure of the decomposed fuel supplied to the fuel inlet exceeds 10 bar, the method includes initiating the introduction of the decomposed fuel into the sub-combustion chamber during the compression stroke of the cylinder.

41. The aforementioned sensor arrangement includes a sub-combustion chamber pressure sensor, and the method is - The method includes receiving an indication of the pressure in the sub-combustion chamber, wherein the method is performed during the compression stroke of the cylinder, The method according to any one of claims 35 to 40, comprising completing the introduction of pre-burned fuel into the sub-combustion chamber before the sub-combustion chamber pressure reaches a predetermined percentage of the pressure of the decomposed fuel supplied to the fuel inlet, as measured upstream of the fuel inlet.

42. The method according to claim 41, wherein the predetermined percentage is 50%.

43. The method according to any one of claims 35 to 42, wherein the fuel inlet comprises a decomposed fuel injector, and the method includes the step of injecting decomposed fuel into the sub-combustion chamber during the compression stroke of the cylinder, wherein the timing of the injection of decomposed fuel is selected to provide a choke flow condition across the decomposed fuel injector.

44. The method according to any one of claims 35 to 43, comprising the step of determining the injection timing of the decomposed fuel based on a real-time measurement of the pressure of the decomposed fuel generated by the decomposition device and a predetermined value of the pressure in the sub-combustion chamber.

45. The method according to any one of claims 35 to 43, comprising the step of determining the injection timing of pre-combustion fuel based on real-time measurements of the pressure of the decomposed fuel generated by the decomposition device and real-time measurements of the pressure in the sub-combustion chamber.

46. - A step of evaluating the pressure of the decomposed fuel upstream of the fuel injector using real-time measurements of the decomposed fuel pressure from a pressure sensor associated with the decomposed fuel, - A step of evaluating the pressure inside the sub-combustion chamber, either by using a predetermined value of the sub-combustion chamber pressure or from real-time measurements of the sub-combustion chamber pressure from a sub-combustion chamber pressure sensor. The method according to any one of claims 35 to 45, comprising the step of initiating the introduction of the decomposed fuel into the sub-combustion chamber via the decomposed fuel injector when the pressure of the decomposed fuel upstream of the decomposed fuel injector is at least twice the pressure in the sub-combustion chamber.

47. - A step of introducing a first spray of ammonia fuel into the main combustion chamber before the combustion gas stream enters the main combustion chamber from the sub-combustion chamber, The method according to any one of claims 35 to 46, as dependent on claim 37, comprising the step of introducing a second spray of ammonia fuel into the main combustion chamber after a first spray of ammonia fuel has been substantially burned in the main combustion chamber.

48. The method according to any one of claims 35 to 47, as dependent on claim 37, comprising the step of initiating and completing the spraying of ammonia fuel into the main combustion chamber before the stream of combustion gas enters the main combustion chamber from the sub-combustion chamber.

49. The method according to any one of claims 35 to 48, as dependent on claim 37, comprising the step of initiating the spraying of ammonia fuel into the main combustion chamber before the stream of combustion gas enters the main combustion chamber from the sub-combustion chamber.

50. The method according to any one of claims 35 to 49, wherein the step of introducing fuel into the main combustion chamber forms an air-fuel mixture, and during the compression stroke of the engine, a portion of the air-fuel mixture flows from the main combustion chamber to the sub-combustion chamber.

51. The method according to any one of claims 35 to 50, wherein the mixture comprises hydrogen and nitrogen and undecomposed ammonia.

52. An engine map, which, when executed by an electronic control device of an engine system, includes an instruction causing the electronic control device to perform the method according to any one of claims 35 to 51.

53. A computer program, when executed by an engine electronic control device of an engine system, includes instructions causing the electronic control device to perform the method according to any one of claims 35 to 51.

54. An internal combustion engine system, - Main combustion chamber, intake port, and exhaust port, - A sub-combustion chamber having fluid communication with the main combustion chamber via at least one orifice, connected to a fuel supply source, and having a fuel inlet configured to allow the introduction of fuel from the fuel supply source to the sub-combustion chamber and to the main combustion chamber via the orifice, - An ignition device positioned together with the sub-combustion chamber and configured to ignite the fuel present in the sub-combustion chamber, wherein the sub-combustion chamber and / or the orifice are configured to enable the generation of a stream of combustion fluid entering the main combustion chamber from the sub-combustion chamber through the orifice, thereby enabling the ignition of the fuel present in the main combustion chamber. An internal combustion engine system comprising: an electronic control device configured to control the ignition device and to control the introduction of fuel into the sub-combustion chamber through the fuel inlet.

55. The internal combustion engine system according to claim 54, wherein the electronic control device is configured to introduce fuel into the sub-combustion chamber at a fuel flow rate that enables fuel supply to the main combustion chamber.

56. The internal combustion engine system according to claim 54 or 55, wherein, at the time of ignition, the fuel present in the main combustion chamber and the fuel present in the sub-combustion chamber are supplied through the same fuel inlet and from the same fuel source.

57. The internal combustion engine system according to claim 56, wherein the fuel is a hydrogen-containing fuel.

58. The internal combustion engine system according to claim 54 or 55, wherein, at the time of ignition, the fuel present in the main combustion chamber is different from the fuel present in the sub-combustion chamber.

59. The internal combustion engine system according to claim 58, wherein the sub-combustion chamber comprises an ammonia fuel injector configured to introduce ammonia fuel into the main combustion chamber through the sub-combustion chamber and through the orifice, and the engine further comprises a pre-combustion fuel injector connected to a source of pre-combustion fuel comprising at least partially hydrogen, wherein the pre-combustion fuel injector is configured to introduce the pre-combustion fuel into the sub-combustion chamber, and the ammonia fuel injector and the pre-combustion fuel injector communicate with and are controlled by the electronic control device.

60. The internal combustion engine system according to claim 59, further comprising a decomposition device connected to an ammonia fuel source and configured to produce a decomposed fuel comprising a mixture of at least nitrogen and hydrogen by decomposing ammonia fuel supplied by the ammonia fuel source during the operation of the engine, wherein the pre-combustion fuel comprises the decomposed fuel received from the decomposition device.

61. The internal combustion engine system according to claim 59 or 60, wherein the electronic control device is configured to control the injection timing and duration of the ammonia fuel injector and the pre-combustion fuel injector so that, at ignition, the hydrogen concentration in the sub-combustion chamber is higher than the hydrogen concentration in the main combustion chamber during operation.

62. The internal combustion engine system according to any one of claims 58 to 61, wherein the electronic control device communicates with a fuel sensor associated with the fuel supply source, and the electronic control device is configured to control the introduction of the fuel through the fuel inlet according to a measurement value received from the fuel sensor.

63. The internal combustion engine system according to claim 62, wherein the electronic control device is configured to control the introduction of fuel based on a predetermined display of the sub-combustion chamber pressure and on a real-time measurement of the fuel pressure provided by the fuel sensor.

64. The internal combustion engine system according to claim 62, wherein the electronic control device is configured to control the introduction of fuel based on real-time measurements of the sub-combustion chamber pressure and the fuel pressure.

65. An internal combustion engine system according to any one of claims 54 to 64, further comprising a pressure boosting injector.

66. A power generation system comprising an internal combustion engine system according to any one of claims 1 to 34 or 54 to 65.

67. A method for supplying fuel to an internal combustion engine having a sub-combustion chamber that is in fluid communication with the main combustion chamber via an orifice, wherein the method is A method comprising introducing fuel into the main combustion chamber by injecting fuel into the sub-combustion chamber using injection parameters configured to create a fuel flow path from the sub-combustion chamber through the orifice into the main combustion chamber.

68. The method according to claim 67, wherein the injection parameter includes at least one of injection mass flow rate, injection pressure, and injection timing.

69. The fuel is supplied from a fuel source, and the method is - Using one or more fuel sensors associated with the fuel supply source, measure one or more characteristics of the fuel supply source, - Communicating the measured characteristics of the fuel supply source to an electronic control device configured to communicate with the sensor and control the introduction of fuel into the sub-combustion chamber, The method according to claim 68, further comprising: determining the injection parameters based on the characteristics of the measured fuel supply source using the electronic control device.

70. The method according to claim 69, wherein the injection parameters include injection timing and injection duration.

71. The method according to claim 69 or 70, wherein the measured value communicated from one or more fuel sensors includes at least one of the pressure and temperature of the fuel supply source.

72. The method according to any one of claims 67 to 71, wherein the fuel introduced into the main combustion chamber via injection into the sub-combustion chamber includes a main combustion chamber fuel, and the method includes the step of introducing a pre-combustion fuel having a different composition from the main fuel into the sub-combustion chamber.

73. The method according to claim 72, wherein the introduction of the pre-combustion fuel into the sub-combustion chamber begins after the introduction of the main combustion chamber fuel into the main combustion chamber.

74. The method according to claim 72 or 73, wherein the main combustion chamber fuel includes ammonia fuel and the sub-combustion chamber fuel includes hydrogen-containing fuel.

75. - A step of providing an ammonia fuel supply source, - A step of operating a cracking device supplied by the ammonia fuel source to produce a cracked fuel containing a mixture of hydrogen and nitrogen, The method according to claim 74, comprising the step of providing the decomposed fuel produced by the decomposition device to the sub-combustion chamber for use as the hydrogen-containing fuel.

76. A method for supplying fuel to an internal combustion engine having a sub-combustion chamber that is in fluid communication with the main combustion chamber via an orifice, wherein the method is - Operate a cracking device supplied by an ammonia fuel source to produce a cracked fuel containing a mixture of hydrogen and nitrogen, - During the compression stroke of the engine, the decomposed fuel is introduced into the sub-combustion chamber, - Ignition of the decomposed fuel present in the sub-combustion chamber to generate a stream of combustion gas that passes through the orifice from the sub-combustion chamber into the main combustion chamber, A method comprising: introducing ammonia fuel into the main combustion chamber via the sub-combustion chamber after the combustion gas has entered the main combustion chamber.

77. A method for supplying fuel to an internal combustion engine having a sub-combustion chamber that is in fluid communication with the main combustion chamber via an orifice, wherein the method is - Operate a cracking device supplied by an ammonia fuel source to produce a cracked fuel containing a mixture of hydrogen and nitrogen, - Introducing the first injection of the decomposed fuel into the sub-combustion chamber, - After the first injection and during the compression stroke of the engine, a second injection of the decomposed fuel is introduced into the sub-combustion chamber. - To ignite the fuel present in the sub-combustion chamber and generate a stream of combustion gas that passes through the orifice and enters the main combustion chamber via the sub-combustion chamber, A method comprising: introducing an injection of ammonia fuel into the main combustion chamber via the sub-combustion chamber after the stream of combustion gas has entered the main combustion chamber.

78. The method according to claim 77, wherein the first injection occurs during the intake stroke of the engine.

79. The method according to claim 77, wherein the first injection occurs during the portion of the engine prior to the compression stroke, and the second injection occurs during the portion of the engine after the compression stroke.

80. An engine map, which, when executed by an electronic control device of an engine system, includes an instruction causing the electronic control device to perform the method according to any one of claims 67 to 79.

81. A computer program, when executed by an engine electronic control device of an engine system, includes instructions causing the electronic control device to perform the method according to any one of claims 67 to 79.

82. A method for modifying an internal combustion engine cylinder, - Attaching a sub-combustion chamber to the cylinder, including connecting the downstream end of the sub-combustion chamber to the fuel inlet of the cylinder in order to provide fluid communication between the sub-combustion chamber and the main combustion chamber in the cylinder, wherein the sub-combustion chamber is equipped with an ignition device configured to enable ignition of the fuel in the sub-combustion chamber during operation. A method comprising connecting a fuel supply source to the fuel inlet of the sub-combustion chamber.

83. The method according to claim 82, wherein the sub-combustion chamber is configured to introduce fuel into the main combustion chamber through the sub-combustion chamber during operation.

84. The method according to claim 82 or 83, wherein the cylinder comprises a main chamber fuel injector configured to introduce fuel into the main combustion chamber either through an intake port communicating with the main combustion chamber or through direct injection into the main combustion chamber.

Images