A system and method for controlling an internal combustion engine

Abstract

A power plant comprises an internal combustion engine (1) and a fuel supply system (100). The internal combustion engine (1) comprises a combustion chamber (3) and a power output member (5), and the power output member (5) is configured and arranged to move when combustion takes place in the combustion chamber; and the combustion chamber (3) comprises a fuel inflow port (6), and an exhaust port (18). The fuel supply system (100) comprises a fuel source (101) fluidly connected to the fuel inflow port (6) via a fuel line (102), and fluid flow control means (103, 104, 105) are arranged in the fuel line for controlling the fuel flow from the fuel source (101) to the fuel inflow port (6). An oxygen supply system (200) comprising a liquid oxygen (LOX) source (201), an oxygen inflow port (7) arranged in the combustion chamber (3), and an oxygen conduit (203) fluidly connecting the oxygen inflow port (7) and the liquid oxygen source (201). The liquid oxygen source (201) and the oxygen conduit (203) are thermally insulated such that oxygen in the system can be maintained at or close to its boiling temperature; and the oxygen conduit (203) comprises oxygen flow control means (204, 205), oxygen temperature control means (206), and oxygen pressure control means (207). A method of controlling the power plant is characterized by controlling one or more of the flowrate, pressure, and temperature of oxygen being injected into the combustion chamber (3) based on the flowrate of fuel being injected into the combustion chamber, in order to obtain a desired power output of the internal combustion engine.

Description

[0001] A system and method for controlling an internal combustion engine

[0002] Technical field of the invention

[0003] The present invention relates to design and operation of internal combustion engines (ICEs) and how to optimize their power output and fuel consumption. More specifically, the invention concerns a power plant as specified in the preamble of claim 1, a method as specified in the preamble of claim 10, and an internal combustion engine as specified in the preamble of claim 16.

[0004] Background of the invention

[0005] The negative consequences of increasing global temperature due to emissions of carbon dioxide (CO2) and other climate gases are now widely accepted, and most nations have published plans for reduction of their emissions of CO2 ahead in this century. The United Nations has taken the lead in these efforts. The goal is to reduce the emissions to limit the temperature increase to 2 °C and preferably 1.5 °C. On the other hand, the world needs energy to maintain the advantages of a high standard of living in the industrialized countries and even more important is to raise the standard of living to an acceptable level in a large part of the world.

[0006] Development of novel energy sources without CO2 emissions during operation, i.e., renewables like wind, waves and sun are required to achieve the goal of global temperature limitation, and so are new investments in nuclear power and energy saving. But the indicated energy sources will be far from sufficient to avoid a fatal energy crisis. Therefore, continued use of fossil fuels will be inevitable. This must, however, be based on carbon capture and storage that removes 85% of the emissions or more. In essence, development of new technologies will be mandatory to avoid both climate crisis and energy crises, both with disastrous consequences for humanity.

[0007] The global manmade emissions of climate gases measured in CO2 equivalents are about 50 billion tonnes. Norway’s part of this is around 0.1%, i.e., around 50 million tonnes. In comparison, the emissions from the world’s shipping fleet are around 20 times more, which indicates a level of 1 billion tonnes that is 2% of the global emission. Therefore, efforts are made to reduce climate gas emissions from shipping, driven by national and international legislation, regulations and taxes. The majority of today’s shipping fleet is powered by internal combustion engines (ICEs). This is a broad term for engines where combustion (i.e. burning of fuel) occurs inside the engine itself, producing a high-temperature gas that drives a piston or a turbine. Examples of common ICE fuels for marine use are diesel, heavy oil fuel, and biofuels. In general, also for non-marine use, most ICEs use diesel or gasoline as fuel for combustion.

[0008] Types of ICE’s are, e.g., explosion engines and piston engines. An explosion engine may for example be a gas turbine engine. In a piston engine, combustion occurs in a chamber (e.g. a cylinder) and moves a piston to generate power. Examples of piston engines are four-stroke engines (Otto-cycle engines) and two-stroke engines. This is the most common type of ICE and includes engines in most cars, motorcycles, and ships. Another type of ICE is the rotary (e.g. Wankel) engine, in which the combustion drives an eccentric rotary element.

[0009] A conventional four-stroke ICE operates as follows: First, in k\ Intake Stroke, the piston moves downward inside the cylinder, increasing the cylinder volume. This allows a fuel-air mixture to enter the combustion chamber (i.e. the cylinder cavity above the piston) through the intake valve. Second, in the Compression Stroke, the intake valve closes, and the piston moves upward, thereby compressing the fuel-air mixture inside the combustion chamber. The high compression ratio ensures efficient combustion. Third, during Fuel Injection, fuel is injected directly into the compressed air inside the combustion chamber. Fuel atomization and distribution are critical for efficient combustion. Fourth, in the Ignition and Combustion stage, the high temperature and high pressure cause the fuel to self-ignite, leading to combustion. The resulting expansion drives the piston downward, producing power.

[0010] The Top Dead Center (TDC) of an ICE is the position where the piston is at its highest point in the cylinder. This occurs when the piston is farthest from the crankshaft and is used as a reference point for setting the ignition timing.

[0011] Different from a four-stroke engine, a two-stroke engine completes a power cycle with two strokes (up and down movements) of the piston during one crankshaft revolution. In prior art ICEs, the fuel is combusted with air as oxidizer. Air comprises approximately 78% nitrogen, 21% oxygen, 1% argon, as well as traces of other gases. This composition of gases is determined by the atmosphere; therefore, all ICEs that use air for combustion are designed and operated accordingly. Consequently, the air limits the design composition of the oxidizing compound to a “single point composition”.

[0012] Turbochargers and superchargers are commonly used for forcing more air - and thereby more oxygen - into the ICE combustion chamber. Consequently, more fuel will be injected into the combustion chamber, resulting in increased power output. Typically, for a diesel-fuelled engine, a turbocharger or supercharger compresses air from ambient pressure (1 bar) to up to 2.5 bar (i.e., a pressure ratio of 2.5: 1). This compression requires energy and therefore represents a parasitic load which must be subtracted from the gross performance or power produced by the engine (expressed in kilowatts; kW) to determine the ICE’s net thermal efficiency. Efficiency is the net produced power divided by the energy content of the fuel. Typically, the thermal efficiency can be improved by approximately 2% by using a turbocharger or a supercharger. Large ICEs (e.g., marine diesel engines) typically achieve maximum thermal efficiencies in the range of 45% to 50%. Similar principles apply for turbocharged or supercharged ICEs using other fuel types.

[0013] Water injection can enhance the efficiency of large diesel engines. Laboratory experiments have shown that spraying water at the engine’s inlet can lead to the following benefits:

[0014] • Fuel Consumption Reduction: o Braking fuel consumption can decrease by up to 10%. o This contributes to overall fuel savings and operational cost reduction.

[0015] • Thermal Efficiency Increase: o Water injection can improve thermal efficiency by up to 4.5%. o Efficient combustion results in better energy utilization.

[0016] In summary, water injection offers a promising approach to enhance ICE performance. Diesel engines have high compression ratios (up to approximately 30: 1). This results in increased cylinder pressures (indicatively 40-70 bar), and elevated air temperatures inside the cylinder. Just before ignition in a large diesel engine, the air inside the cylinder is under tremendous pressure. As the piston travels upward during the compression stroke, the air that once filled the cylinder now occupies only a small fraction of its original volume. This intense compression causes the air to become super-heated, reaching temperatures exceeding 400 °C. At such high pressures and temperatures, the diesel fuel ignites spontaneously, initiating the combustion process. The actual pressure just before ignition can vary based on factors like compression ratio, engine load, and specific engine design. However, peak cylinder pressures near the top dead center can range from approximately 20 bar for light loads to over 70 bar for engines at full power.

[0017] The atomized diesel fuel injected into this high-pressure environment ignites spontaneously due to the extreme heat. During the process of combustion in an internal combustion engine (ICE), the gas temperature in the cylinder often reaches quite a high value, up to 2530 °C. A considerable amount of heat is transferred to the walls of the combustion chamber. Therefore, proper cooling, especially for the walls of the combustion chamber, is necessary.

[0018] The peak cylinder pressure in a large diesel engine just at combustion can exceed 200 bar in high-performance diesel engines. This intense pressure occurs during the power stroke when the fuel ignites spontaneously, driving the piston downward and converting heat energy into mechanical work. The skilled person will know that spark plugs are used in ICEs without spontaneous ignition.

[0019] Characteristic operation parameters for state-of-the-art ICEs are presented in Table 1 below.

[0020] Table 1 The figures of Table 1 indicate a need for cooling of the cylinder wall and strengthening of the cylinders to withstand the pressure and temperature, and thereby selection of materials. It should be understood that these aspects apply to four-stroke ICEs as well as to two-stroke ICEs.

[0021] There is thus a need for a system and method by means of which the efficiency of an ICE can be maximised, CO2 emissions from the ICE are reduced, and the combustion chamber walls are exposed to lower temperatures. Summary of the invention

[0022] The invention is set forth and characterized in the main claim, while the dependent claims describe other characteristics of the invention.

[0023] It is thus provided a power plant, comprising an internal combustion engine and a fuel supply system; wherein the internal combustion engine comprises a combustion chamber and a power output member, and the power output member is configured and arranged to move when combustion takes place in the combustion chamber; and the combustion chamber comprises a fuel inflow port, and an exhaust port; wherein the fuel supply system comprises a fuel source fluidly connected to the fuel inflow port via a fuel line, and fluid flow control means are arranged in the fuel line for controlling the fuel flow from the fuel source to the fuel inflow port; wherein the power plant is characterized by: an oxygen supply system comprising a liquid oxygen (LOX) source, an oxygen inflow port arranged in the combustion chamber, and an oxygen conduit fluidly connecting the oxygen inflow port and the liquid oxygen source, and wherein the liquid oxygen source and the oxygen conduit are thermally insulated such that oxygen in the system can be maintained at or close to its boiling temperature; and the oxygen conduit comprises oxygen flow control means, oxygen temperature control means, and oxygen pressure control means.

[0024] In one embodiment, the power plant further comprises a CO2 supply system comprising a liquid CO2 (LCO2) source, a CO2 inflow port arranged in the combustion chamber, and a CO2 conduit fluidly connecting the CO2 inflow port and the LCO2 source, wherein the CO2 inflow port and the LCO2 source are thermally insulated such that the CO2 can be maintained at or close to its boiling temperature; and the CO2 conduit comprises LCO2 flow control means, CO2 temperature control means, and CO2 pressure control means. In one embodiment, the power plant further comprises an exhaust recirculation conduit connected between an exhaust line and the CO2 conduit downstream of the LCO2 flow control means, CO2 temperature control means, and CO2 pressure control means, and the exhaust line is connected to the exhaust port.

[0025] In one embodiment, the power plant further comprises a water supply conduit connected between a water source and the CO2 conduit downstream of the LCO2 flow control means, CO2 temperature control means, and CO2 pressure control means.

[0026] In one embodiment, the power plant further comprises an oxygen flow sensor, an oxygen pressure sensor and an oxygen temperature sensor arranged in the oxygen conduit.

[0027] In one embodiment, the internal combustion engine comprises a movable energy transfer device arranged in the combustion chamber and configured to impart energy to the power output member, and a rotation sensor arranged and configured to monitor rotation, imbalance, and / or vibrations of the power output member, and an accelerometer arranged to monitor movement of the energy transfer device.

[0028] In one embodiment, the power plant further comprises a control system configured for controlling the oxygen flow control means, oxygen temperature control means, and oxygen pressure control means based on data provided by one or more of the oxygen flow sensor, oxygen pressure sensor, oxygen temperature sensor, rotation sensor, and accelerometer. The control system can be configured for controlling the LCO2 flow control means, CO2 temperature control means, and CO2 pressure control means, to control flow through the CO2 injection port. In one embodiment, the control system comprises artificial intelligence and a machine-learning system, whereby algorithms within the control system can improve automatically based on recorded data.

[0029] It is also provided a method of controlling the power plant according to the present invention, characterized by controlling one or more of the flowrate, pressure, and temperature of oxygen being injected into the combustion chamber based on the flowrate of fuel being injected into the combustion chamber, in order to obtain a desired power output of the internal combustion engine. The method can further comprise injecting a controlled volume of one or more of CO2, recirculated exhaust gas, or water, into the combustion chamber to dilute the oxygen in the combustion chamber in order to control the combustion temperature. In one embodiment, the method further comprises: measuring the power generated by a power output member of the internal combustion engine; determining the corresponding energy generated by the fuel injected into the combustion chamber; comparing the generated power with the generated energy; and based on this comparison, adjusting one or more of pressure and temperature of oxygen being injected into the combustion chamber to obtain maximum efficiency for the internal combustion engine.

[0030] In one embodiment, the method further comprises measuring of temperature and pressure in the combustion chamber and / or vibrations in the internal combustion engine. The method can be executed by one or more algorithms in a control system, and artificial intelligence can be utilized to enable the algorithms to improve automatically based on recorded data.

[0031] It is also provided an internal combustion engine having a combustion chamber with a fuel injection port, an oxygen injection port, a CO2 injection port, and no air intake, and means for controlling the flow of oxygen and CO2, water, and / or recycled exhaust gas into the combustion in order to emulate air.

[0032] The invented system and method employ oxyfuel combustion and provides an improved operation of ICEs by injecting oxygen with a selected and controlled phase state, pressure, and temperature, instead of air.

[0033] An advantage of the invention is that the ICE exhaust consists of water and CO2 which facilitates carbon capture and storage (CCS). The invention offers a cost-favourable, easy to adapt, and reliable solution that facilitates the capture of CO2 emissions from the world’s shipping fleet, but also one that can be used for on land vehicles and aviation.

[0034] The invention presents an opportunity of forcing much more oxygen into an ICE combustion chamber than turbos and superchargers can achieve; i.e., up to whatever injection pressure is desired for maximizing the ICE efficiency taking into consideration the mechanical and thermal strengths of existing ICEs.

[0035] The invention can achieve and probably exceed the benefits of water injection by injecting cold oxygen and cold CO2 into the combustion chamber. Using a mixture of very cold LOX and LCO2 as basis, efficient control of the flame of the combustion is achieved, and thus control of the temperature in the combustion chamber wall.

[0036] In addition to supplying the combustion chamber with a controlled and desired amount of oxygen for combustion, the invented system can also replace a turbocharger or supercharger, and constitutes an improvement over these as it provides the freedom to select injection pressure(s) to whatever is required to maximize efficiency of an ICE.

[0037] The invention can be applied both for four-stroke and two stroke ICE.

[0038] The invention can be directly adapted to existing ICEs by exchanging the supply of oxygen from air to pure oxygen and when necessary, recirculate some of the captured CO2 as a substitute for nitrogen for dilution and thereby control of the combustion temperature. Other dilution methods involve exhaust gas recirculation (EGR) and water injection.

[0039] The main feature of the invention is a system that allows injection of oxygen into the cylinders of ICEs in the desired phase and at desired temperature and pressure of that phase for optimizing the operation of the ICE. In cases where injection of CO2 is necessary for dilution of the oxygen to prevent too high temperature in the cylinder at combustion the control of phase and pressure and temperature at injection, can be done in the same way as for oxygen. As pointed out above for air combustion, the composition of air is given with oxygen 21% as a fixed input to the design basis for ICEs and at a temperature range of normally within -30 °C to +30 °C given by the ambient air.

[0040] The purity range for oxygen in oxyfuel applications typically falls between 99.5% and 99.9%. This high level of purity ensures efficient combustion and minimizes impurities that could affect the process. But in some cases, the purity can be reduced, say to 97% or lower, based on a cost benefit / disadvantage (caused by the impurities) analysis.

[0041] The invention removes the restriction of a “single point composition” and “narrow temperature range” for the design basis. Replacing air by oxygen as in the present invention, offers a set of free variables for optimizing the design and operation of ICEs in addition to making it facilitate Carbon Capture and Storage (CCS). The new free variables are:

[0042] • Selection of phase (liquid, supercritical, gas) of oxygen at injection point.

[0043] • Selection of temperature of oxygen at injection point.

[0044] • Selection of composition of the mix of oxygen and CO2 for dilution of the oxygen to control the flame temperature of the combustion. The composition can vary from mimicking air which makes possible a seamless transition from air to oxyfuel, or the CO2 content can be reduced to design more efficient engines and reduce their size and weight for a given performance. The maximum reduction is to zero and in the future ICEs can be designed and operated at higher temperature and pressure, and therefore with reduced cylinder diameter and the stroke length, i.e. smaller and lightweight engines.

[0045] With LOX as oxygen source, the oxygen injection pressure can be controlled and changed by a liquid pump, and the injection pressure can therefore be higher than in the prior art. This allows the injection or charging pressure to be set higher than the limited charging achievable by a turbocharger (1.5 bar, pressure ratio 1.5: 1), a supercharger (2.5 bar, pressure ratio 2.5: 1) by compressing ambient air, which is an energy expensive process.

[0046] When the LOX pump is arranged upstream of a temperature-controlled heat exchanger, injection pressure and temperature can both be selected to achieve the desired combination. The liquid pump is thus used for “charging” the combustion chamber. The invented system is therefore referred to as a “Pumpcharger”, and the invented method is referred to as “Pumpcharging”.

[0047] The invented system and method can be used for increasing and optimizing the efficiency when installed in an ICEs and be used for improving design of future ICEs allowing for higher pressure at ignition, reduced size of cylinders and lighter weight and volume.

[0048] The invention can be applied to existing ICEs to facilitate CCS from the exhaust in a known way, by compression and cooling.

[0049] Use of oxyfuel combined with CO2 for substituting nitrogen gives new opportunities for design of optimum ICEs. Instead of simply mimicking the operation of an air-supplied ICE, which is known in the art, future designs can optimize the ICE operation and design based on availability of liquid oxygen (LOX) at -183 °C at one bar and liquid CO2 (LCO2) at a pressure of approximately 15 to 20 bar and a temperature between approximately -20 and -10 °C, which are approximately the boiling points at the indicated pressures.

[0050] In one embodiment, a fraction of water can be injected together with oxygen and fuel in order to partly or completely substituting CO2.

[0051] Considerable energy is consumed to produce the liquid oxygen and liquid CO2. This energy is partly stored in these liquids in the form of a cold reservoir that can be recovered by utilization for internal cooling of the cylinders and perhaps also external cooling.

[0052] Injection of cold oxygen and CO2 into the combustion chamber allows for higher compression of the fluid content in the chamber before ignition (and subsequent combustion) because the temperature before compression starts is much lower than for ambient air. While ambient air typically has a temperature in the region of 20 °C, the liquid oxygen can have a temperature as low as towards -183 °C. In this extreme case the temperature before compression will be more than 200 °C lower than for ambient air. Lowered injection temperature will allow for a corresponding higher compression of the fluids in the cylinder before ignition resulting in higher performance of ICEs. Implementing the invented system and method in existing air-supplied ICEs, could require injection of CO2 for preventing overheating, as a carefully controlled and customized mixture of oxygen and CO2 will mimic the normal air operation, and the ICEs can be operated with oxygen injection without further modifications.

[0053] The materials used in the cylinders for the state-of-the-art air operated ICE engines are typically:

[0054] 1. Cast Iron: Widely used due to its excellent wear resistance and thermal conductivity.

[0055] 2. Steel: Preferred for high-performance engines because of its superior strength and durability.

[0056] 3. Aluminium Alloys: Used in lightweight engines for their low weight and good thermal conductivity.

[0057] Additionally, Inconel and Nichrome iron alloys are sometimes employed for cylinder liners due to their high-temperature strength, wear resistance, and durability. Future ICE designs could make use of the invention to make more efficient engines.

[0058] For diesel and air entering the combustion process at 25 °C and 1 atm pressure, the adiabatic flame temperature for diesel combustion is approximately 1950 °C. In Table 1, a much higher peak temperature, i.e., 2530 °C is indicated due to combustion pressure of 70 bar and more.

[0059] The adiabatic flame temperature for combusting diesel with pure oxygen at 1 bar will be much higher due to no dilution by nitrogen. And thereby peak temperature in the cylinder will be similarly much higher, indicatively double that of diesel and air. Exact calculation can be done when having the composition of the diesel and the ignition pressure.

[0060] A further development that will be possible by using the invention can be building oxyfuel ICEs in high temperature and pressure resistant materials to utilize the higher injection pressure and thereby the higher pressure at ignition that Pumpcharging can give compared to turbo and supercharging. Compared to these types of charging the Pumpcharger can give a much higher density of the injected oxygen, up to approximately 1000 kg / m3in the extreme case that LOX is injected. The higher mass of oxygen in the volume of a cylinder, will result in correspondingly higher mass of fuel. Therefore, the combustion energy in a given cylinder volume can be much higher than using air and turbo and superchargers. It can be concluded that the combined effect of higher peak pressure and more mass will result in higher peak temperatures and pressure that enhances efficiency by allowing more work extraction during expansion. The volume of the engine cylinder can be significantly reduced compared to air supported combustion. This will reduce the size and weight of the engine and therefore the cost.

[0061] Specially designed composite materials can be used in combination 3D printing to achieve the required strength to realize the potentially large improvement in efficiency by operating at the higher pressure and temperature that the invention opens for as indicated above.

[0062] A large benefit of using liquid oxygen and liquid CO2 is that it gives freedom to select the injection pressure. A high injection pressure, i.e. above the 2.5 bar (which is achievable by compressing air), to say 25 bar or more, will result in less cylinder volume for the resulting peak pressure, for instance 500 bar, just before ignition and 1500 bar of the combustion gases just after ignition with a temperature of estimated 4000 °C. Such operation will result in a large increase in performance and efficiency, which can be realized by the good cooling offered by cold oxygen and CO2 combined with selection of materials.

[0063] Another potential advantage of the invention is that cold oxygen can be used for cooling of the ICE cylinders externally, for example in ducts around the cylinders. If oxygen is produced on-board, for example by an Air Separation Unit (ASU), the by-product cold nitrogen can be used for the same purpose. Further, injection of cold oxygen will have a beneficial cooling effect inside the cylinder that will allow higher compression ratio and combustion pressure resulting in enhanced efficiency.

[0064] As mentioned above, the invention using a mixture of cold LOX and LCO2 as basis, will allow for efficient control of the internal walls of the combustion chamber.

[0065] The invention is not about carbon capture and storage (CCS), but about maximizing the operation of oxyfuel ICEs, which wholly and partly can compensate for the CCS by reduced fuel cost. However, because the exhaust of an oxyfuel motor consists of water vapor and gaseous CO2 with only small fractions of contaminants, it is easy to perform carbon capture and storage by known technology. An oxyfuel ICE can therefore be without CO2 emission.

[0066] Substituting air combustion of fuel of internal combustion engines (ICE) with oxygen combustion makes it easy to capture CO2 because the exhaust consists only of water vapor and CO2, and the CO2 can be captured simply by condensation.

[0067] Oxyfuel combustion of ICE engines is not yet a proven commercial solution, but rather in a research and development phase. To get acceptance for oxyfuel for ICE engines it will be important to find a solution for achieving the highest possible efficiency at all modes of operation of the future ICE engines in operation. Efficiency can be continuously measured by metering the power output and comparing it with the latent energy of the fuel consumption. The control system comprises an algorithm for this functionality.

[0068] Further research and testing will be needed to develop algorithms for controlling the operational parameters that endeavour running the ICE at maximum efficiency at all modes of operation. These parameters are (i) injection pressure (i.e. charging of the cylinder), and (ii) the phase and temperature of the oxygen.

[0069] In its simplest form efficiency can be determined simply by measuring the shaft power and compare it with the corresponding energy of the injected fuel. The algorithm can be improved by including the cylinder temperature and pressure and vibration. The intention is that the algorithm shall be learning and self-improving by use of artificial intelligence (Al).

[0070] The advantages of CCS facilitated by the invention compared to other possible CO2 emission free solutions demonstrate the invention’s industrial application:

[0071] The advantages of the invention compared to other possible CO2 emission free or low CO2 emission technical solutions are:

[0072] 1. Hydrogen: The electric energy consumption per energy unit (e.g. kWh) of hydrogen and thereby the cost of production is very high. Hydrogen cannot be used for excising ICEs, and the ICEs of existing vessels must either be exchanged to yet not developed hydrogen ICEs or fuel cells, which will be costly and need several years of development and qualification.

[0073] It shall be added that storage and transport of liquid hydrogen which has a boiling point of -253 °C poses a technical challenge that must be solved.

[0074] 2. Ammonia: Ammonia is produced by combining hydrogen and nitrogen to form NH3. This will add energy consumption to the already consumed energy for production of hydrogen and nitrogen and thereby make the cost per energy unit of ammonia even higher than for hydrogen.

[0075] Storage and transport of ammonia is not a challenge because the boiling point is -33.5 °C. However, ammonia is poisonous and special precautions are necessary

[0076] 3. Normal air combustion ICEs with amine capture: Existing ICEs can reduce the CO2 emissions by about 90% of the exhaust by the proven technology of carbon capture by amine.

[0077] The amine capture plant requires a large footprint and height and has a high weight that all together makes it unfit for placement on board ships of practical reasons as it will significantly reduce the payload capacity.

[0078] Another drawback is that the electricity burden for CO2 removal using amine scrubbing approaches around 113 kWh per tonne of CO2 removed, and the heat needed for regeneration range from 2.6 to 2.8 GJ / tonne CO2.

[0079] Compared to the three above solutions the invention has many benefits: a) 100% capture compared to amine capture with about 90%. b) Existing ICEs in ships and vehicles can be used, and the solution has a potential for significantly enhanced performance by future development. c) The cost of fuel will be much lower than using hydrogen or ammonia. d) Transport and storage of liquid oxygen (boiling point -183 °C) is proven technology. In contrast, hydrogen (H2) must be cooled to -253 °C, which is a considerable challenge. e) Capture of CO2 from the exhaust by condensation by controlling the pressure and temperature is a simple and low-cost technology compared to an amine plant. f) No additional tanks for on board storage of captured CO2 will be necessary because the storage tanks for LOX can be used as they are emptied.

[0080] In cases where the oxygen is supplied by an on-board air separation unit, ASU, (could be the right solution for large ships with long sailing time), CO2 storage tanks will be necessary, but an advantage in this case is that the cooling capacity of the waste product nitrogen can be used for external cooling of the engine cylinders and for cooling of the CO2 of the exhaust for condensation.

[0081] Brief description of the drawings

[0082] These and other characteristics of the invention will become clear from the following description of the invention, given as a non-restrictive example, with reference to the attached schematic drawings, wherein:

[0083] Figure l is a process flow diagram illustrating the present invention;

[0084] Figure 2 is a phase diagram for oxygen; and

[0085] Figure 3 is a phase diagram for carbon-dioxide.

[0086] Detailed description of embodiments of the invention

[0087] The following description may use terms such as “horizontal”, “vertical”, “lateral”, “back and forth”, “up and down”, “upper”, “lower”, “inner”, “outer”, “forward”, “rear”, “underneath”, “above”, etc. These terms generally refer to the views and orientations as shown in the drawings and that are associated with a normal use of the invention. The terms are used for the reader’s convenience only and shall not be limiting.

[0088] The present invention is based on a conscious and controlled use of the phase diagram for oxygen for selecting the desired phase at which oxygen is to be injected into the ICE and selecting the desired and appropriate injection temperature and pressure for maximizing the ICE performance and efficiency.

[0089] Referring to figure 1, the invented system comprises in the illustrated embodiment a power plant comprising an internal combustion engine (ICE) 1 and three energy supply systems: a fuel supply system 100, an oxygen supply system 200, and a carbon-di oxide (CO2) supply system 300. The ICE and the energy supply systems are monitored and controlled by a control system 16, based on data from sensors arranged and configured as described below. Information provided by the sensors and other equipment and devices is transmitted to the control system 16 by known means and devices (not illustrated). Likewise, signals from the control system 16 are transmitted by known means and devices. It should be understood that the figures only show parts and features that are necessary to illustrate the invention. For example, power sources, electrical wires, actuators, certain valves, etc., are not shown in the figures. For the purpose of this description, the word “sensor” shall imply that the sensor comprises or is connected to transmitters, or other devices or systems for communication with the control system.

[0090] In the illustrated embodiment, the ICE 1 comprises a piston 2 arranged for reciprocating movement in a cylinder 4. The piston 2 is connected to a movable power output member 5, which in the illustrated embodiment can be a rotatable shaft, such as a crankshaft, via parts (not illustrated) and in a manner well known in the art. As figure 1 illustrates a reciprocating engine, the piston 2 is illustrated at a bottom dead center (BDC) position 9 and a top dead center (TDC) position 10.

[0091] Inflow ports 6, 7, 8 are arranged in the wall of the cylinder 4, providing respective openings through which fluid can flow (e.g. injected) into a cavity 3 above the piston 2. This cavity constitutes a combustion chamber 3. Although not illustrated, it should be understood that the ICE can comprise a mixing chamber upstream of the combustion chamber 3. The combustion chamber 3 volume varies with the piston 2 movement, and an accelerometer (sensor) 11 is connected to the cylinder 4 for sensing piston movement and detecting imbalance and vibrations. The ICE can comprise other sensors, such as a vibration metering sensor, a temperature sensor, and a pressure sensor, enabling instantaneous as well as long-term continuous condition monitoring, in order to optimize operating conditions for operation over an extended period of time.

[0092] In the illustrated embodiment, the movable power output member 5 and the combustion chamber 3 are on opposite sides of the piston 2. The combustion chamber can have other configurations, for example between compressor(s) and turbine(s) in a turbine engine or turboshaft engine, in which case the movable power output member can be turbine shaft. A rotation sensor 19 is arranged for monitoring the power output member rotational movement.

[0093] A pressure sensor 12 and a temperature sensor 13 are connected to the combustion chamber 3, configured for sensing and transmitting ignition pressure and ignition temperature, respectively. The inflow ports 6, 7, 8 are arranged and configured for feeding fluids into the combustion chamber 3, as is described below.

[0094] Also fluidly connected to the combustion chamber 3 is an exhaust port 18 though which combustion gases are expelled. An exhaust line 14 is connect to the exhaust port 18 and can be arranged to convey the exhaust gases to a treatment facility (not shown), e.g., for condensation, removal of impurities, and capture of water and CO2. An oxygen sensor 15 is arranged in the exhaust line 14, for monitoring oxygen content in the exhaust gases.

[0095] One of the above-mentioned ports, a fuel inflow port 6, is fluidly connected to the above-mentioned fuel supply system 100. In the illustrated embodiment, the fuel supply system 100 comprises a fuel source 101 connected to the fuel inflow port 6 via a fuel conduit 102 whereby fuel can be supplied to the combustion chamber at a desired pressure and flowrate. A fuel pump 103, a fuel flow control valve 104, and a fuel flow sensor 105, are therefore arranged in the fuel conduit 102. In one embodiment, the fuel comprises diesel or gasoline and the fuel source comprises a reservoir such as one or more tanks. Another one of the above-mentioned ports, an oxygen inflow port 7, is fluidly connected to the above-mentioned oxygen supply system 200. In the illustrated embodiment, the oxygen supply system 200 comprises a liquid oxygen (LOX) source 201 connected to the oxygen inflow port 7 via an oxygen conduit 203. The LOX source can be an air separation unit (ASU) or a tank. The LOX source 201 and oxygen conduit 203 (e.g. piping) are thermally insulated such that the oxygen can be maintained at or close to its boiling temperature (e.g. -183 °C at 1 bar in the LOX source 201 and -153 °C if the pressure of LOX is pumped up to 20 bar before injection).

[0096] Reference number 202 denotes a vent line for boil-off gas (BOG) from within the LOX source. The oxygen supply system further comprises an LOX pump device 204, a LOX flow control device 205, an oxygen heat exchanger 206, and an oxygen pressure control device 207, all arranged in the first fluid conduit 203. These components are thermally insulated as well, to maintain the oxygen at or close to its boiling temperature (e.g. -153 °C at 20 bar, for example after the pump device 204).

[0097] In embodiments, the LOX flow control device 205 and the oxygen pressure control device 207 can be valves. In the oxygen heat exchanger 206, LOX is in thermal contact with a warming medium such as ambient air, sea water, fresh water, oil, or other warming medium, whereby the temperature of the gaseous oxygen at the oxygen inflow port 7 can be controlled. As an option, for improved temperature control of oxygen injected into the combustion chamber3, an insulated bypass conduit 211 comprising control valves (not shown) can be arranged in the oxygen conduit 203 to bypass the oxygen heat exchanger 206. The oxygen pressure control device 207 is controllable to give the gaseous oxygen the desired pressure at the oxygen inflow port 7. The LOX heat exchanger 206 and the oxygen pressure control device 207 can be controlled based on signals provided by one or more of an oxygen flow sensor 208, an oxygen pressure sensor 209, and an oxygen temperature sensor 210, all arranged downstream of the heat exchanger and the pressure control device, preferably in the vicinity of the oxygen inflow port 7. When the power plant is in operation, the desired pressure and temperature (and hence the phase state) of the oxygen at the oxygen inflow port 7 can thus be controlled as desired. Yet another one of the above-mentioned ports, a CO2 inflow port 8, is fluidly connected to the above-mentioned CO2 supply system 300. In the illustrated embodiment, the CO2 supply system 300 comprises a liquid CO2 (LCO2) source 301 connected to the CO2 inflow port 8 via a CO2 conduit 303. In a practical embodiment, the CO2 source (e.g. a reservoir such as a tank) and CO2 conduit (e.g. piping) are thermally insulated such that the CO2 can be maintained below its boiling temperature (e.g. between -20 and -30 °C at between 50 and 60 bar). The CO2 supply system further comprises an LCO2 pump device 302, an LCO2 flow control device 304, a CO2 heat exchanger 305, and a CO2 pressure control device 306, all arranged in the second fluid conduit 303. In embodiments, the LCO2 flow control device 304 and the CO2 pressure control device 306 can be valves. In the CO2 heat exchanger 305, LCO2 is in thermal contact with a warming medium such as ambient air, sea water, fresh water, oil, or other warming medium, whereby the temperature of the CO2 (gaseous or liquid state, or a mixture) at the CO2 inflow port 8 can be controlled. As an option, for improved temperature control of CO2 injected into the combustion chamber3, an insulated bypass conduit 311 comprising control valves (not shown) can be arranged in the CO2 conduit 303 to bypass the CO2 heat exchanger 305.

[0098] The CO2 pressure control device 306 is controllable to give the gaseous CO2 the desired pressure at the CO2 inflow port 8. The CO2 heat exchanger 305 and the CO2 pressure control device 306 can be controlled based on signals provided by one or more of a CO2 flow sensor 307, a CO2 pressure sensor 309, and an CO2 temperature sensor 308, all arranged downstream of the heat exchanger and the pressure control device, preferably in the vicinity of the CO2 inflow port 8.

[0099] In an embodiment, the oxygen conduit 203 and the CO2 conduit 303 are thermally insulated the entire distance between the reservoir and the respective inflow port in the ICE, to virtually eliminate temperature drop. The fuel conduit 102 can also be thermally insulated in the same manner in order to be able to control the fuel injection temperature at fuel injection port 6. In an embodiment, a thermally insulated heat exchanger (not shown) is arranged in the fuel conduit 102, whereby the fuel temperature at fuel injection port 7 can be controlled. In an embodiment, the system comprises one or more vibration sensors that, together with pressure sensors, temperature sensors, flow sensors, provide information to optimize the operation of the ICE in different modes.

[0100] The control system 16 can be configured to control operational parameters, such as, but not limited to: a. Injection pressure and temperature and flow at the oxygen injection port 7 by controlling flow and discharge pressure of the pump LOX pump 204 to achieve the desired pressure and controlling the temperature of oxygen out of the oxygen heat exchanger 206 to achieve the desired temperature. b. Injection pressure and temperature and flow at the CO2 injection port 8 by controlling flow and discharge pressure of the LCO2 pump 302 to achieve the desired pressure and controlling the temperature of CO2 out of the CO2 heat exchanger 305. c. Injection of fuel that gives the required performance of the ICE at any mode of operation and keeps the injection of oxygen in the right proportion for complete (100%) combustion that can be stochiometric proportion or some excess of oxygen, say 1%, to ensure 100% and prevent soot from forming. d. Calculate peak combustion temperature by the temperature sensor or sensors on the cylinder walls and the temperature profile along the cylinder. e. Calculate peak pressure in the cylinder and the pressure profile along the cylinder based on the injected mass of oxygen, fuel, and CO2, the calculated temperature at any piston position and the temperature.

[0101] The control system can comprise artificial intelligence (Al) to continually improve its performance by adaptive learning based on acquired data.

[0102] During operation, the invented system is powered by the fuel supply system 100 which feeds fuel into the ICE as described above. Although the embodiment illustrated in figure 1 shows a combustion chamber 3 with individual injection ports for fuel, oxygen and CO2, it should be understood that the fluids can be injected in one of several manners, e.g.: 1. Into a mixing chamber for all fluids (fuel, oxygen, as well as CO2, and / or water and / or recycled exhaust gas)

[0103] 2. A mixing chamber for two of the fluids (e.g., oxygen and CO2) and direct injection of the third (fuel) or other configurations of two in mixing chamber and the third injected directly

[0104] 3. Direct injection of all phases into the cylinder combustion chamber.

[0105] When LOX and LCO2 are injected into a cavity, they will not be two liquids but a two- phase mix of the two, i.e. there will be some gas that prevents the piston from being crushed if it is meeting an incompressible liquid in the compression stage. This also prevents the cylinder from being cracked.

[0106] A conventional diesel engine does not have a separate mixing chamber; instead, the fuel and air mix within the combustion chamber during the compression stroke.

[0107] When injecting oxygen and CO2 and thereby fuel is injected at a higher pressure than what is possible by air compression, e.g. 2.5 bar, it will be necessary to either: a) Control the inflow ports such that the volume to be compressed does not give a too high pressure just before ignition and just after ignition, or b) Adjust the mass, and thereby the volume, down so as to not generate too high pressures.

[0108] The peak combustion temperature can be controlled by controlling (in most cases, increasing) the injection of CO2 in order to dilute oxygen. The pressure and temperature sensors transmit signals to the control system that controls the pumps and heat exchangers to give the desired pressure and temperature combinations of both oxygen and CO2 at their respective injection ports. As an alternative or supplement to injecting CO2 from the LCO2 source 301, water or / and exhaust gas can be injected in the CO2 injection port 8. In this embodiment, an exhaust recirculation conduit 40 comprising an exhaust recirculation control valve 41 is arranged between the exhaust line 14 and the CO2 conduit 303 downstream of the CO2 pressure control device 306, or / and a water supply conduit 44 comprising a water control valve 43 is arranged between a water source 42 and the CO2 conduit 303 downstream of the CO2 pressure control device 306. A CO2 flow control valve 310 is arranged in the CO2 conduit 303 upstream of where the exhaust recirculation conduit 40 and the water supply conduit 44 are connected to the CO2 conduit 303.

[0109] The invented system exceeds the function of a supercharger by making it possible to select the injection pressure as high as desired such that the pressure above the piston just before ignition is as desired for maximizing performance and efficiency. The invented system can also make water injection superfluous by cooling by injecting oxygen and CO2 at low temperatures.

[0110] If for instance, as an extreme example, the oxygen is in the liquid phase when injected, virtually no compression work will be needed, resulting in a significantly increased efficiency by eliminating the compression work of the engine’s pistons. Reduced compression work and thereby increased efficiency will also result if injection in the supercritical phase or gas phase at a desired high pressure, for instance at the level of 30 bar to 50 bar. The resulting peak pressure just after combustion can be 150 to 200 bar or more. The same is valid if CO2 is needed to be injected for dilution of the oxygen and thereby controlling the peak combustion temperature.

[0111] Supplying the pressure of the oxygen and CO2 by pumps saves considerably energy compared to compression by the ICE piston. If the compression work by the piston is too low to give the necessary temperature for ignition, spark plugs must be applied.

[0112] The invented system allows for much higher cylinder charging than what is achieved by turbocharging or supercharging, because the LOX pump and LCO2 pump handle an incompressible medium, not gaseous air. This opens for future design and use of advanced materials that can tolerate higher peak pressures than the present 150 to 200 bar and thereby increase performance and efficiency. By using cold oxygen and if necessary, CO2, the peak combustion temperature can be controlled to be within the tolerable even at high peak pressure. In the future materials can be used that allows for higher combustion temperatures than presently. In this way the opportunities given by having LOX and LCO2 can be utilized.

[0113] Temperature sensors in or on the cylinder walls will make it possible for the control system to calculate the maximum temperature at combustion and the temperature profile along the cylinder and of the piston. This information will be transmitted to the control system to adjust the temperature of the injected oxygen and CO2 to find the desired balance between wanted cooling of the cylinder and at the same time avoid thermal shock or too high thermal stress when injecting the fluids (fuel, and O2, as well as CO2, water and / or recycled exhaust gas).

[0114] Use of the phase diagrams of oxygen and CO2 is essential for selecting temperature and pressure to achieve the phase state (gas, liquid, supercritical) best suited for the operation of different types of ICEs, existing and future designs based on the invention, and the temperature and pressure of the oxygen and CO2 at injection. The invented system enables navigation in the phase diagrams of oxygen and CO2 for selecting optimum phase and temperature and pressure of the phase for achieving optimum operating performance, and efficiency at any mode of operation of the ICE.

[0115] When LOX and LCO2 are injected together with fuel into the combustion chamber, some gas will be a part of the mixture and therefore there is no risk for the piston being crushed by meeting an incompressible mixture during the compression stroke. Calculations should be performed from case to case for different proportions of LOX, LCO2, and fuel.

[0116] Modes of operation of the ICE are for instance idle, dead slow, half speed and full speed and others.

[0117] The invented system and method are applicable for two- and four-stroke ICEs and the different carbonaceous fuels that are used for ICEs, e.g., bunker oil, diesel, gasoline, natural gas and others.

[0118] Use of the diagram and navigating in them is essential for the invention by selecting the optimum phase (liquid, compressible liquid, supercritical or gas) and selecting the optimum temperature and pressure for that phase at the injection point of the oxygen into the ICE cylinders, and if cold oxygen is used for external cooling of the cylinders.

[0119] Use of the diagram is fundamental for the invention by selecting the optimum phase (liquid, supercritical or gas) and selecting the optimum temperature and pressure for that phase at the injection point of the CO2 into the ICE cylinders, and if cold CO2 is used for external cooling of the cylinder. The invented system and method can maximize operation of oxyfuel ICEs by selecting the phase at the injection point by a combination of pressure and temperature that maximizes the performance and efficiency. Because the invented system can set the pressure by pumping an incompressible fluid (LOX), it does not have the limitations of turbochargers and superchargers that increases the pressure of 1 bar air. The oxygen supply system injects oxygen from a LOX source 201 (tank or ASU) at a combination of pressure and temperature that gives maximized conditions for the operation of the ICE. This can be achieved by a LOX pump 204 followed by a LOX heat exchanger 206 that makes it possible to navigate in the oxygen phase diagram to select phase (liquid, supercritical or gas) and injection pressure and temperature of the selected phase in a combination at the oxygen injection port 7. Selection of phase, temperature and pressure at injection can maximize performance and efficiency of the ICE for a given fuel injection. This is defined as “instant maximized operation conditions”.

[0120] The peak temperature of the combustion and temperature profile along the cylinder can be used to maximize the combustion by efficient utilization of the fuel.

[0121] The control system can also calculate the peak pressure and pressure at the different positions of the piston along the cylinder during the strokes. This can be used to help maximize combustion efficiency.

[0122] The invention can be used on four-stroke engines and two-stroke engines, and any ICE.

[0123] In the embodiments described above, various features and details are shown in combination. The fact that several features are described with respect to a particular example should not be construed as implying that those features by necessity have to be included together in all embodiments of the invention. Conversely, features that are described with reference to different embodiments should not be construed as mutually exclusive. As a person skilled in the art readily will understand, embodiments that incorporate any subset of features described herein and that are not expressly interdependent have been contemplated by the inventor and are part of the intended disclosure. However, explicit description of all such embodiments would not contribute to the understanding of the principles of the invention, and consequently some permutations of features have been omitted for the sake of simplicity or brevity.

Claims

Claims1. A power plant, comprising an internal combustion engine (1) and a fuel supply system (100); wherein the internal combustion engine (1) comprises a combustion chamber (3) and a power output member (5), and the power output member (5) is configured and arranged to move when combustion takes place in the combustion chamber; and the combustion chamber (3) comprises a fuel inflow port (6), and an exhaust port (18); wherein the fuel supply system (100) comprises a fuel source (101) fluidly connected to the fuel inflow port (6) via a fuel line (102), and fluid flow control means (103, 104, 105) are arranged in the fuel line for controlling the fuel flow from the fuel source (101) to the fuel inflow port (6); wherein the power plant is characterized by: an oxygen supply system (200) comprising a liquid oxygen (LOX) source (201), an oxygen inflow port (7) arranged in the combustion chamber (3), and an oxygen conduit (203) fluidly connecting the oxygen inflow port (7) and the liquid oxygen source (201), and wherein the liquid oxygen source (201) and the oxygen conduit (203) are thermally insulated such that oxygen in the system can be maintained at or close to its boiling temperature; and the oxygen conduit (203) comprises oxygen flow control means (204, 205), oxygen temperature control means (206), and oxygen pressure control means (207).

2. The power plant of claim 1, further comprising a CO2 supply system (300), comprising a liquid CO2 (LCO2) source (301), a CO2 inflow port (8) arranged in the combustion chamber (3), and a CO2 conduit (303) fluidly connecting the CO2 inflow port (8) and the LCO2 source (301), wherein the CO2 inflow port (8) and the LCO2 source (301) are thermally insulated such that the CO2 can be maintained at or close to its boiling temperature; and the CO2 conduit (303) comprises LCO2 flow control means (302, 304), CO2 temperature control means (305), and CO2 pressure control means (306).

3. The power plant of claim 2, further comprising an exhaust recirculation conduit (40) connected between an exhaust line (14) and the CO2 conduit (303) downstream of the LCO2 flow control means (302, 304), CO2 temperature control means (305), and CO2 pressure control means (306), and the exhaust line (14) is connected to the exhaust port (18).

4. The power plant of claim 2, further comprising a water supply conduit (44) connected between a water source (42) and the CO2 conduit (303) downstream of the LCO2 flow control means (302, 304), CO2 temperature control means (305), and CO2 pressure control means (306).

5. The power plant of any one of claims 1-4, further comprising an oxygen flow sensor (208), an oxygen pressure sensor (209) and an oxygen temperature sensor (210) arranged in the oxygen conduit (203).

6. The power plant of any one of claims 1-5, wherein the internal combustion engine (1) comprises a movable energy transfer device (2) arranged in the combustion chamber (3) and configured to impart energy to the power output member (5), and a rotation sensor (19) arranged and configured to monitor rotation, imbalance, and / or vibrations of the power output member (5), and an accelerometer (11) arranged to monitor movement of the energy transfer device (2).

7. The power plant of claim 6, further comprising a control system (16) configured for controlling the oxygen flow control means (204, 205), oxygen temperature control means (206), and oxygen pressure control means (207) based on data provided by one or more of the oxygen flow sensor (208), oxygen pressure sensor (209), oxygen temperature sensor (210), rotation sensor (19), and accelerometer (11).

8. The power plant of claim 7, wherein the control system (16) is configured for controlling the LCO2 flow control means (302, 304), CO2 temperature control means(305), and CO2 pressure control means (306), to control flow through the CO2 injection port (8).

9. The power plant of any one of claims 7 and 8, wherein the control system (16) comprises artificial intelligence and a machine-learning system, whereby algorithms within the control system can improve automatically based on recorded data.

10. A method of controlling the power plant of any one of claims 1-9, characterized by controlling one or more of the flowrate, pressure, and temperature of oxygen being injected into the combustion chamber (3) based on the flowrate of fuel being injected into the combustion chamber, in order to obtain a desired power output of the internal combustion engine.

11. The method of claim 10, further comprising injecting a controlled volume of one or more of CO2, recirculated exhaust gas, or water, into the combustion chamber (3) to dilute the oxygen in the combustion chamber in order to control the combustion temperature.

12. The method any one of claims 10 or 11, further comprising: measuring the power generated by a power output member (5) of the internal combustion engine (1); determining the corresponding energy generated by the fuel injected into the combustion chamber (3); comparing the generated power with the generated energy; and based on this comparison, adjusting one or more of pressure and temperature of oxygen being injected into the combustion chamber (3) to obtain maximum efficiency for the internal combustion engine (1).

13. The method of claim 12, further comprising measuring of temperature and pressure in the combustion chamber (3) and / or vibrations in the internal combustion engine (1).

14. The method of any one of claims 10-13, wherein the method is executed by one or more algorithms in a control system (16).

15. The method of claim 14, wherein artificial intelligence is utilized to enable the algorithms to improve automatically based on recorded data.

16. An internal combustion engine (1) having a combustion chamber (3) with a fuel injection port (6), an oxygen injection port (7), a CO2 injection port (8), and no air intake, and means for controlling a flow of oxygen, CO2, water, and / or recycled exhaust gas into the combustion in order to emulate air.

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