A staged fuel supply system and a method of controlling fuel injection in stages

Abstract

The application discloses a staged fuel supply system and a staged fuel injection control method, and relates to the field of fuel supply devices of internal combustion engines. The method is characterized in that two types of fuels are supplied in the same engine working cycle, the first fuel is first transported to form lean mixture with the overall excess air coefficient greater than 1, and the first stage combustion of approximate constant volume heat release is completed near the top dead center; after the combustion reaches a preset progress, the second fuel is injected into the high-temperature area in the cylinder to generate a local rich combustion core and a peripheral oxidation envelope, the quasi-isobaric heat release is realized in the initial stage of expansion by adjusting the injection rate, and the whole cylinder is maintained in a lean combustion state. The application is suitable for gaseous fuel, liquid fuel and their combination which can realize lean premixing and local direct injection respectively.

Description

Technical Field

[0001] This invention relates to the field of internal combustion engine fuel supply device technology, specifically to a staged fuel supply system and a staged fuel injection control method. Background Technology

[0002] The common combustion modes in engines mainly include premixed combustion and diffusion combustion. Premixed combustion can release heat within a shorter crankshaft angle and has a higher degree of isochoric combustion. Under lean conditions, the premixed combustion temperature is lower, which is beneficial to reduce the formation of thermal nitrogen oxides, but it is limited by factors such as lean-burn stability limit, misfire, cycle fluctuation and abnormal combustion under high load.

[0003] Diffusion combustion or locally rich combustion has the advantages of high ignition reliability and the ability to adjust the combustion rate through the injection process. In a rich combustion environment, the oxygen concentration and local temperature are limited, which helps to suppress the formation of some nitrogen oxides; however, if the entire cylinder is in a rich combustion state or the products of locally rich combustion cannot be further oxidized, carbon monoxide, unburned fuel, soot, or other incomplete combustion products are easily produced.

[0004] Therefore, both the single lean-burn premixed mode and the single diffusion-rich mode have limitations in terms of combustion stability, emissions, or thermal efficiency. If the cylinder can maintain overall lean combustion while forming a localized rich core only within a limited time and space, and an oxidation envelope region capable of continuing to entrain oxygen is set around the localized rich core, then the low-temperature, low-NOx characteristics of global lean combustion and the low-oxygen reaction characteristics of localized rich combustion can be utilized simultaneously, while reducing the risk of incomplete combustion caused by localized rich combustion.

[0005] From a thermodynamic cycle perspective, rapid heat release near top dead center is beneficial for improving isochoric combustion, but excessively rapid pressure rise may be limited by knocking, peak burst pressure, and mechanical load. Releasing some heat at a controlled rate in the early expansion stroke can prolong the high-pressure work phase, but excessively delayed heat release will reduce expansion utilization. A high geometric compression ratio is beneficial for increasing the expansion ratio and improving cycle efficiency, but it will increase the compression termination temperature and the risk of abnormal combustion. The Miller cycle can reduce the effective compression ratio and compression termination temperature by changing the effective compression initiation time, thus partially decoupling the geometric compression ratio from the effective compression ratio; however, the Miller cycle may also reduce the effective charge or compression work, requiring compensation through a second-stage combustion heat release process. Ammonia fuel contains no carbon, but has low reactivity, slow flame propagation speed, and produces fuel-type NOx, unburned ammonia, and other pollutants during combustion. Control issues.

[0006] Existing single-path fuel injection systems for internal combustion engines have inherent hardware and electronic control deficiencies in terms of staged fuel supply, high-temperature zone directional injection, multi-fuel safety adaptation, and closed-loop supply control, as detailed below: Traditional fuel supply devices have only a single delivery path, which cannot complete the two differentiated gas supply actions of premixed lean fuel and localized rich fuel in the cylinder in sequence. They cannot independently control the total amount of premixed fuel and the directional injection rate, making it difficult to match the two-stage gas supply sequence requirements of "first global lean premixing, then localized rich injection". Conventional fuel injectors lack targeted installation positions and nozzle parameter designs, and cannot accurately target the high-temperature already burned zone in the cylinder, behind the flame front, and the jet wake to deliver fuel in a directional manner. They can only inject indiscriminately throughout the entire area and cannot build a localized rich core and an outer oxidation envelope based on the injection space distribution, resulting in insufficient fuel space distribution control capabilities. Existing supply electronic control only uses a fixed crankshaft injection pulse pattern to complete the gas supply control. It cannot dynamically correct the timing, quantity, and rate of the second fuel injection based on the feedback of the previous combustion progress, making it difficult to match the differentiated gas supply rhythm corresponding to the two stages of heat release, which are approximately isochoric and quasi-isobaric, resulting in low fuel supply metering matching accuracy. For low-activity nitrogen-containing fuels like ammonia, existing supply equipment lacks dedicated pipelines for pressurization and stabilization, overall shut-off, pressure relief, inert purging, and leak detection. It also lacks the hardware for creating a locally rich ammonia reduction environment. (The last sentence appears to be incomplete and unrelated to the preceding text.) Emission control is difficult; conventional supply systems cannot be linked with Miller variable valve timing mechanisms to match the gas supply volume, and cannot compensate for the charge and power loss caused by the Miller cycle through staged gas supply; and there is no staged reduction or cut-off logic for gas supply under abnormal conditions such as misfire, knock, fuel leakage, and insufficient injection conversion, resulting in poor long-term operational safety of the entire fuel supply equipment.

[0007] In summary, the existing single-channel fuel supply hardware and supporting electronic control cannot achieve time-sharing, zone-based, and graded gas supply, directional injection in high-temperature areas, and safe adaptation to multiple fuels. The degree of freedom in fuel supply regulation, metering accuracy, adaptability to operating conditions, and operational safety all have significant shortcomings. There is an urgent need for a graded fuel injection supply system to solve the inherent defects in the above-mentioned fuel supply level. Summary of the Invention

[0008] This invention addresses the shortcomings of existing single-path fuel supply devices for internal combustion engines, which only support single-cycle homogeneous fuel supply and lack independent hardware architectures for premixed lean combustion and partial rich combustion. Furthermore, these devices lack an in-cylinder high-temperature target area adaptation structure for the injector, traditional electronic control cannot dynamically adjust the second fuel injection parameters based on real-time combustion feedback, lack a dedicated safe ammonia fuel supply branch, cannot coordinate the Miller cycle to match the two-stage gas supply, and lack a graded gas supply degradation protection mechanism under abnormal operating conditions. Overall, these devices suffer from poor fuel supply control flexibility, cycle metering accuracy, multi-fuel adaptability, and operational safety. To address these issues, this invention proposes a graded fuel supply system and a staged fuel injection control method. The invention achieves these technical problems through the following technical solutions: Option 1: This invention proposes a staged fuel supply system, which is used to deliver fuel to an internal combustion engine in stages. According to the staged injection supply, a mixture distribution with global lean combustion and local rich combustion is formed in the cylinder. The system includes an engine body, a first fuel supply module, an ignition module, a second fuel supply module, at least one second fuel injector connected to the combustion chamber, an electronic control module, and a combustion state detection module. The first fuel supply module is configured to inject and deliver the first fuel into the cylinder intake port, scavenging port, or low-pressure cylinder during the early compression phase, so that the first fuel mixes with air to form a lean mixture with a global excess air coefficient λoverall greater than 1. The second fuel supply module includes at least one second fuel injector, which is arranged near the cylinder head, cylinder sidewall or pre-combustion chamber, and is used to inject second fuel into the target high-temperature reaction zone in the combustion chamber. After injection, a fuel-rich core with an excess air coefficient λlocal of less than 1 is formed locally. The fuel-rich core entrains oxygen-containing gas to form an oxidation envelope zone. The combustion state detection module includes at least one of a cylinder pressure sensor, a crankshaft position sensor, a speed sensor, and an exhaust component sensor, and is used to collect in-cylinder combustion progress and heat release state feedback signals in real time. The electronic control module is electrically connected to the first fuel supply module, the second fuel injector, and the combustion state detection module. The electronic control module has built-in graded supply control logic, that is, the electronic control module is used to control the first fuel supply module to form a globally lean mixture and control the ignition module to implement isochoric first-stage combustion. The electronic control module is also used to control the second fuel injector to inject second fuel into the target high-temperature reaction area after the first-stage combustion reaches the predetermined combustion progress, forming a locally fuel-rich core and an outer oxidation envelope zone, and to make the second-stage combustion quasi-isobaric exothermic by controlling the second fuel injection rate.

[0009] Furthermore, a preferred embodiment is provided, wherein the first fuel supply module and the second fuel supply module supply the same fuel in stages, or two fuels with different chemical compositions; the first fuel supply module is a lean premixed gas or volatile liquid fuel, and the second fuel supply module is a gas or liquid fuel that can be directly injected into the cylinder to form a local fuel-rich zone.

[0010] Furthermore, a preferred embodiment is provided, wherein the first fuel supply module and the second fuel supply module include at least one of natural gas, methane, hydrogen, ammonia, methanol, ethanol, dimethyl ether, gasoline, diesel, biofuel, synthetic fuel, and mixtures thereof.

[0011] Furthermore, a preferred embodiment is provided in which the second fuel supply module is implemented using at least one of single injection, main injection plus supplementary injection, segmented injection, or injection rate shaping, in order to match the second-stage heat release rate with the pressure drop rate caused by piston expansion.

[0012] Furthermore, in a preferred embodiment, the second fuel injector is mounted on the cylinder head, cylinder sidewall, or pre-combustion chamber body, and the second fuel injector is provided with one or more injection holes.

[0013] Furthermore, a preferred embodiment is provided, wherein the combustion progress in the first stage is determined by at least one of CA10, CA50, cumulative heat release ratio, in-cylinder pressure rise rate, and the time when the flame reaches the calibrated position; the quasi-isobaric heat release determination criteria for the second stage are that the deviation of the in-cylinder pressure from the target pressure does not exceed the calibrated value, or the absolute value of the pressure change rate per unit crankshaft angle does not exceed the calibrated value.

[0014] Option 2: A dual-fuel staged fuel injection control method, the method being implemented based on the staged fuel supply system described in Option 1, the method comprising the following steps: Step 1: Control the first fuel supply module to deliver the first fuel, form a lean mixture with a global excess air coefficient greater than 1 and ignite it, and complete the first stage of combustion near the top dead center, which is approximately isochoric. Step 2: Collect in-cylinder combustion feedback signals, and after determining that the first stage of combustion has reached the predetermined progress, control the second fuel injector to inject the second fuel into the target high-temperature reaction area in the cylinder to form a local fuel-rich core and an outer oxidation envelope area. Step 3: Adjust the timing, rate, and quantity of the second fuel injection to ensure that the second stage releases heat at near-isobaric pressure in the early stage of expansion, and that the overall excess air coefficient of the cylinder remains greater than 1 throughout the entire process. Step 4: Adjust the fuel supply parameters for the two stages of the subsequent cycle based on real-time cylinder pressure, cycle fluctuation, and exhaust component data; Step 5: Monitor the operation of the supply system and engine body in real time, and adjust or cut off the second fuel supply in stages when abnormalities occur.

[0015] Furthermore, a preferred embodiment is provided, wherein in step 1, the first stage of combustion is approximately isochoric heat release through lean combustion premixing, and the second stage is approximately isobaric heat release through fuel-rich combustion.

[0016] Furthermore, a preferred embodiment is provided, wherein the target high-temperature reaction zone in step 2 includes at least one of the following: the already burned high-temperature zone formed by the first stage combustion, the region behind the flame front, the wake region of the first fuel jet, the high-temperature zone formed by the ignition jet, and the region where the temperature, oxygen concentration, and remaining reaction time meet the requirements of the second fuel conversion.

[0017] Furthermore, a preferred embodiment is provided in which the engine in step 5 adopts a geometric compression ratio higher than that of a reference engine, and the effective compression ratio is lower than the geometric compression ratio through the Miller cycle.

[0018] The advantages of this invention are: The staged fuel supply system and phased fuel injection control method described in this invention utilize global lean combustion to reduce the average combustion temperature and thermal NOx formation tendency in the first stage, and improves the heat utilization near top dead center through near-isochoric rapid heat release. This invention forms a locally rich combustion core only in a limited area, utilizing a low-oxygen environment to reduce local peak temperature and some NOx formation tendency, while avoiding severe incomplete combustion caused by overall cylinder rich combustion. An oxidation envelope region is set around the rich combustion core, which is beneficial for the continued oxidation of CO, unburned hydrocarbons, soot precursors, unburned ammonia, and other intermediate products, thereby reconciling the contradiction between local rich combustion and complete fuel conversion. The composite heat release method of near-isochoric in the first stage and quasi-isobaric in the second stage balances efficient heat release near top dead center with continuous high-pressure work during the expansion stroke, which is beneficial for improving cycle work capacity under the constraint of the highest burst pressure. The high geometric compression ratio and Miller cycle partially decouple the expansion ratio and effective compression ratio, which is beneficial for improving expansion work capacity and reducing compression termination temperature; the quasi-isobaric heat release in the second stage helps compensate for some power loss caused by the Miller cycle. For ammonia-containing fuels, the localized ammonia-rich, low-oxygen reaction environment and the surrounding oxidation structure can simultaneously affect the generation and consumption of fuel-type NO, the conversion of unburned ammonia, and... It is controlled, and therefore has a more significant comprehensive application value compared to ordinary fuel combinations.

[0019] In the staged fuel supply system and phased fuel injection control method described in this invention, the first branch completes the pre-supply of the global lean mixture through the intake manifold, scavenging manifold, or early compression low-pressure injection; the second branch is equipped with a customizable directional injector, which is fixedly mounted on the cylinder head, cylinder sidewall, or pre-combustion chamber body. The nozzle orientation, orifice diameter, spray cone angle, and injection pressure can be precisely matched according to the high-temperature reaction zone in the cylinder, delivering the second fuel only to the already burned high-temperature zone, behind the flame front, and the jet wake, naturally forming a locally rich combustion core through hardware-based zoned gas supply. The injection timing, injection quantity, and injection position of the two-stage supply branches can be independently adjusted, no longer constrained by the timing of a single path. The fuel supply adjustment capability in the time and space dimensions is significantly improved compared to traditional single-path supply equipment, and it can flexibly match the two-stage gas supply requirements of "first global lean premixing, then locally rich directional injection".

[0020] The graded fuel supply system and staged fuel injection control method described in this invention include a complete set of hardware for the second fuel supply module, comprising an ammonia storage tank, a pressure boosting and stabilizing unit, an electromagnetic main shut-off valve, a pressure relief branch, an inert gas purging pipeline, and an ammonia leak detection sensor. Under normal operating conditions, ammonia fuel can be directionally delivered to the high-temperature, low-oxygen region inside the cylinder, forming a locally rich ammonia-reducing gas supply layer through the directional injection hardware. If an ammonia leak occurs in the detection pipeline or injector, the electronic control system instantly closes the main shut-off valve and automatically initiates inert gas purging to empty the pipeline of residual ammonia, eliminating the risk of continuous leakage of flammable ammonia. The entire supply system requires no large-scale hardware modifications and is compatible with natural gas, hydrogen, methanol, gasoline, diesel, ammonia, and various biofuel blends. One set of supply hardware adapts to multiple fuel engine models, significantly reducing the R&D and procurement costs of multi-fuel engine supply equipment and significantly improving equipment versatility.

[0021] In the staged fuel supply system and staged fuel injection control method described in this invention, the electronic control unit establishes bidirectional signal interaction with the variable valve and exhaust valve timing module, reads Miller degree parameters in real time, and synchronously adjusts the first premixed fuel equivalence ratio, the second total fuel injection quantity, and the staged supply ratio according to the changes in the effective intake charge. The effective charge loss caused by the Miller cycle is compensated by staged fuel delivery. Under high geometric compression ratio and low effective compression ratio conditions, the total in-cylinder fuel supply can still be maintained stably by relying on the second stage continuous injection. The entire supply system can maintain stable air supply characteristics in the low, medium, and high full load ranges.

[0022] The graded fuel supply system and staged fuel injection control method described in this invention have a second fuel injector hardware that is compatible with various supply forms, including single main injection, main injection and post-injection supplementary injection, multi-segment injection, and injection rate shaping. The electronic control automatically switches the injection mode according to the real-time cylinder pressure drop slope. Under high load, the segmented injection duration is extended, and fuel is delivered at a uniform speed to match the high-pressure working range. Under low load, micro-precise injection is used to avoid fuel escape and waste caused by excessive injection, reduce the loss of unburned fuel with exhaust during the gas supply process, improve the effective utilization rate of actual fuel supply, and reduce losses in the fuel delivery process.

[0023] The present invention is also applicable to single fuels or combinations of multiple fuels that form a combustible lean mixture in the first stage and a locally rich reaction zone by in-cylinder injection in the second stage, particularly ammonia fuel, natural gas, hydrogen, methanol and combinations thereof. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the staged fuel supply system described in Embodiment 1.

[0025] Figure 2 This is a schematic diagram of the first and second stage combustion zones in the engine cylinder as described in Embodiment 1.

[0026] Figure 3 This is a PV schematic diagram of the composite cycle of the first stage isochoric heat release and the second stage quasi-isobaric heat release as described in Embodiment 1.

[0027] Figure 4 This is a schematic diagram of the NO emission area for the lean-rich combustion method described in Implementation Method 1.

[0028] Figure 5 This is a schematic flowchart of the staged combustion control method described in Implementation Method 1.

[0029] Figure 6 This is a schematic diagram illustrating a preferred embodiment of the ammonia fuel described in Embodiment 1.

[0030] The engine body 1, combustion chamber 7, first fuel supply module 8, ignition module 10, second fuel supply module 11, electronic control module 13, combustion status detection module 14, and exhaust valve timing module 16 are included. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them.

[0032] Implementation Method 1, see [link] Figures 1 to 6This embodiment describes a staged fuel supply system and a phased fuel injection control method. The aim is to provide a phased combustion method and engine system that integrates global lean combustion, localized rich combustion, a near-isochoric first stage, a quasi-isobaric second stage, and a high-compression-ratio Miller cycle to balance combustion stability, NOx control, fuel conversion integrity, and thermal efficiency. Within the same working cycle, the method ensures that the first fuel and air form a lean mixture with a global excess air coefficient greater than 1, and performs rapid combustion in the first stage near top dead center, concentrating the main heat release in the crankshaft angle range where cylinder volume changes little, resulting in near-isochoric heat release. After the first stage reaches a predetermined combustion progress, the second fuel is injected into the high-temperature already-burned zone, the area behind the flame front, or the jet wake region. Under the condition that the cylinder maintains overall lean combustion, a locally rich core with an excess air coefficient less than 1 and its surrounding oxidation envelope region are formed. The second stage, through injection rate and combustion rate control, achieves quasi-isobaric heat release in the early expansion phase. The first and second fuels can be the same or different, and are suitable for gaseous fuels, liquid fuels, and combinations thereof that can achieve lean-burn premixing and local direct injection zones, respectively. Preferably, a high geometric compression ratio and Miller cycle are used to reduce the effective compression temperature and increase the expansion work capacity; when the second fuel contains ammonia, the locally rich ammonia and low-oxygen environment and the peripheral oxidation structure are beneficial to balancing the stable conversion of ammonia, NOx, unburned ammonia, and... control.

[0033] During the same working cycle of the engine, a first fuel is supplied to the cylinder, forming a lean mixture with air where the overall excess air coefficient (λoverall) is greater than 1. The first fuel can be supplied through the intake manifold, scavenging manifold, low-pressure in-cylinder injection, or early compression injection.

[0034] The lean mixture is ignited and the first stage of combustion is implemented. By controlling the first fuel equivalence ratio, ignition or tinderbox timing, turbulence intensity, and mixing uniformity, the main heat release in the first stage is concentrated in the first crankshaft angle range near top dead center. Within this range, the cylinder volume change is lower than the first calibration value, thus giving the first stage approximately isochoric heat release characteristics.

[0035] Once the predetermined combustion progress is reached in the first stage, the target high-temperature reaction zone within the combustion chamber is determined, and second fuel is injected into the target high-temperature reaction zone via a second fuel injector. The target high-temperature reaction zone can be the already burned high-temperature zone, the area behind the flame front, the wake zone of the first fuel jet, the high-temperature zone of the ignition jet, or a region where the temperature, oxygen concentration, and remaining reaction time meet the requirements for the conversion of the second fuel.

[0036] After the second fuel is injected, a fuel-rich core is formed with a local excess air coefficient λlocal less than 1. Moving outward from the fuel-rich core, the concentration of the second fuel decreases and the entrainment of oxygen-containing gas increases, forming an oxidation envelope region where the local excess air coefficient gradually increases and reaches or exceeds 1 in at least some areas. This constitutes a spatially layered combustion structure of "global lean combustion – locally fuel-rich core – peripheral oxidation envelope".

[0037] By controlling the timing, rate, pressure, quantity, duration, and number of injections of the second fuel injection, the second stage of combustion is positioned in the early stage of the expansion stroke, and the heat release rate of the second stage is matched with the pressure drop rate caused by piston expansion, so that the cylinder pressure is maintained within the target pressure range or the pressure change rate is maintained within the calibrated range, thereby forming quasi-isobaric heat release.

[0038] The first stage, approximately isochoric heat release, and the second stage, quasi-isobaric heat release, together constitute a composite, multi-stage cycle. The first stage is used to establish an efficient and rapid initial heat release and a target high-temperature reaction environment, while the second stage is used to prolong high-pressure work, increase fuel energy input, and regulate local reaction pathways.

[0039] The first and second fuels can be different stages of the same fuel supply, or they can be different fuels. The first fuel should be able to form a lean combustible mixture with air; the second fuel should be able to form a locally rich combustion zone through directional in-cylinder injection. Optional fuels include natural gas, methane, hydrogen, ammonia, methanol, ethanol, dimethyl ether, gasoline, diesel, biofuels, synthetic fuels, and mixtures thereof.

[0040] Preferably, the engine employs a higher geometric compression ratio than the benchmark model, and reduces the effective compression ratio through the Miller cycle. For a four-stroke engine, this can be achieved by advancing or delaying the intake valve closing time; for a two-stroke engine, it can be achieved by adjusting the exhaust valve closing time, the scavenging duration, or the effective compression initiation time.

[0041] High geometric compression ratio is used to increase expansion ratio; Miller cycle is used to reduce compression end temperature, knock tendency and the risk of pressure rise in the first stage; the second stage quasi-isobaric heat release is used to compensate for part of the effective charge or power loss caused by Miller cycle and prolong the high-pressure expansion work process.

[0042] When the second fuel contains ammonia, it is preferable to inject the ammonia into the already combusted zone, where the temperature is high and the oxygen concentration is lower than that of the fresh mixture, to create a reducing reaction environment in the locally ammonia-rich core. Nitrogen-containing intermediates such as NH2 and NH formed by ammonia decomposition can simultaneously participate in the NO generation and consumption reactions. By adjusting the local temperature, oxygen concentration, equivalence ratio, and residence time, it is beneficial to increase the relative contribution of the NO consumption pathway; the outer oxidation envelope zone is used to promote the continued conversion of unburned ammonia and nitrogen-containing intermediates.

[0043] When both the first and second fuels are ammonia, the first part of the ammonia can be supplied in a lean premixed or partially premixed manner, and the first stage of combustion can be achieved by using pre-combustion chamber jet, high-energy ignition, or high-reactivity micro-ignition of fuel; the second part of the ammonia is directly injected after the high-temperature zone is formed in the first stage to form a locally rich ammonia second stage.

[0044] When the primary fuel is natural gas, hydrogen, or methanol, and the secondary fuel is ammonia, the first stage is used to rapidly establish a high-temperature reaction environment, and the second stage achieves carbon-free or low-carbon energy replenishment and nitrogen emission regulation through localized rich combustion of ammonia.

[0045] The electronic control unit determines the control parameters for the first and second stages based on cylinder pressure, crankshaft angle, combustion phase, heat release rate, maximum pressure rise rate, cycle fluctuation, and emission signals, and performs degraded control in case of misfire, knocking, pressure over-limit, incomplete conversion of local rich fuel products, or fuel leakage.

[0046] Example 1: Staged Combustion of the Same Fuel The first and second fuels use the same fuel. The first part of the fuel forms a globally lean mixture with air during the intake or early compression phase and burns rapidly near top dead center; the second part of the fuel, after reaching the predetermined combustion progress in the first stage, enters the target high-temperature reaction zone through direct injection into the cylinder, forming a locally fuel-rich core and an outer oxidation envelope zone.

[0047] This implementation is applicable to fuels that can combine lean premixed combustion and direct injection capabilities. The controller, based on cylinder pressure and piston position, keeps the primary heat release in the first stage within a range of small volume changes, and maintains the in-cylinder pressure during the initial expansion phase by shaping the injection rate in the second stage.

[0048] Example 2: Staged Combustion of Different Fuels The first fuel uses a gaseous or volatile fuel with good lean-burn propagation ability, while the second fuel uses a fuel that can ignite rapidly in a high-temperature region and form a locally rich combustion zone. The first stage is responsible for establishing the high-temperature combustion zone, and the second stage is responsible for prolonging heat release and increasing output power.

[0049] By altering the energy distribution ratio between the primary and secondary fuels, it is possible to match lean-burn stability, peak pressure, quasi-isobaric duration, and emissions. The secondary fuel can be injected in a single main injection or a combination of main injection and supplementary injection.

[0050] Example 3: Natural gas lean combustion – ammonia partial rich combustion The primary fuel is natural gas. During scavenging, intake, or early compression, natural gas forms a lean premixed gas with air, which is then ignited by a small amount of highly reactive fuel or a pre-combustion chamber jet. After the first stage of natural gas combustion creates a high-temperature, already-burned zone, ammonia is directly injected into this zone.

[0051] The local excess air coefficient in the ammonia spray core is less than 1, while the outer periphery entrains the residual oxygen after natural gas combustion, forming an oxidation envelope zone. The locally rich ammonia and low-oxygen environment helps limit the further oxidation of some nitrogen-containing intermediates to NO, and allows intermediates such as NH2 and NH to participate in the NO consumption reaction; the outer region is used for further conversion of unburned ammonia and nitrogen-containing intermediates.

[0052] The scheme described in this embodiment, when combined with the Miller cycle and high compression ratio, achieves an indicated thermal efficiency improvement of approximately 5.8%, and NOx has the potential to reach the IMOTIer III limit. The above values ​​correspond only to the relevant model and boundary conditions.

[0053] Example 4: Staged Combustion of All-Ammonia Lean-Fuel to Rich-Fuel Combustion Both the first and second fuels are ammonia. The first portion of ammonia is supplied through the intake manifold, scavenging manifold, or early compression injection to form a lean mixture, and is ignited by a pre-combustion chamber jet, high-energy ignition, or a small amount of highly reactive fuel to form a first stage of approximately isochoric combustion.

[0054] After the high-temperature reaction zone is formed in the first stage, the second part of ammonia is injected into the cylinder under high pressure to form a locally rich ammonia core and an outer oxidation envelope zone. If necessary, flow enhancement, scavenging, or increasing turbulence intensity can be used to expand the lean-burn stability range of ammonia in the first stage.

[0055] Example 5: High Compression Ratio Miller Composite Cycle The engine employs a high geometric compression ratio, which is reduced by adjusting the intake valve closing early, the intake valve closing late, the exhaust valve closing late, or the scavenging process to lower the effective compression ratio. In the first stage, the lean-burn mixture rapidly releases heat near top dead center; in the second stage, fuel is continuously injected during the initial expansion phase, causing cylinder pressure to change slowly within the target range.

[0056] The controller uses the maximum burst pressure, maximum pressure rise rate, knock index and exhaust temperature as constraints to jointly optimize the geometric compression ratio, Miller degree, first-stage combustion phase and second-stage injection pattern.

[0057] Example 6: Closed-loop control and anomaly protection The electronic control unit calculates CA10, CA50, heat release rate, maximum pressure rise rate, and quasi-isobaric duration based on cylinder pressure, and corrects the first fuel equivalence ratio, ignition timing, second fuel injection rate, and Miller degree for the next cycle based on these parameters.

[0058] In the event of misfire, knocking, excessive pressure, incomplete fuel conversion in the second stage, or fuel leakage, the controller will reduce or stop the second fuel injection, cancel supplemental injection, adjust the first stage combustion phase, reduce the load, or switch to a safe fuel mode. For ammonia fuel, it will also close the main ammonia shut-off valve and perform pressure relief or purging.

[0059] In summary, this implementation method significantly improves the flexibility of fuel delivery adjustment by optimizing the staged fuel injection supply hardware and supporting electronic control, employing two independent supply branches and directional injectors that can be matched with high-temperature zones; it effectively improves the metering accuracy of cyclic fuel supply by relying on combustion feedback closed-loop control of injection parameters; it is equipped with a full-process ammonia fuel safety supply component, which has strong versatility for multiple fuels and multiple machine models; the electronic control linkage Miller mechanism compensates for charge loss, broadens the range of stable gas supply conditions, and at the same time, it is equipped with staged fault gas supply protection logic to improve equipment operation safety; and the multiple injection schemes can reduce fuel delivery escape loss.

[0060] Those skilled in the art will understand that the above description is merely a preferred embodiment of the present invention, and the features described in the various embodiments and / or technical solutions of this disclosure can be combined or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. This is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0061] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended technical solutions are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the present invention. Clearly, those skilled in the art can make various modifications and variations to the present invention without departing from its spirit and scope. Thus, if these modifications and variations of the present invention fall within the scope of the present invention and its equivalents, the present invention also intends to include these modifications and variations.

Claims

1. A staged fuel supply system, characterized in that, The system is used to deliver fuel to an internal combustion engine in stages. According to the staged injection supply, a mixture distribution with global lean combustion and local rich combustion is formed in the cylinder. The system includes an engine body (1), a first fuel supply module (8), an ignition module (10), a second fuel supply module (11), at least one second fuel injector connected to the combustion chamber, an electronic control module (13), and a combustion state detection module (14). The first fuel supply module (8) is configured to inject and deliver the first fuel into the cylinder intake port, scavenging port or low-pressure cylinder in the early stage of compression, so that the first fuel mixes with air to form a lean mixture with a global excess air coefficient λoverall greater than 1. The second fuel supply module (11) includes at least one second fuel injector, which is arranged near the cylinder head, cylinder sidewall or pre-combustion chamber, for injecting second fuel into the target high-temperature reaction zone in the combustion chamber. After injection, a fuel-rich core with an excess air coefficient λlocal of less than 1 is formed locally, and oxygen-containing gas is entrained around the fuel-rich core to form an oxidation envelope zone. The combustion state detection module (14) includes at least one of a cylinder pressure sensor, a crankshaft position sensor, a speed sensor, and an exhaust component sensor, and is used to collect in-cylinder combustion progress and heat release state feedback signals in real time. The electronic control module (13) is electrically connected to the first fuel supply module (8), the second fuel injector, and the combustion state detection module (14), respectively. The electronic control module (13) has built-in graded supply control logic. That is, the electronic control module (13) is used to control the first fuel supply module (8) to form a global lean mixture and control the ignition module (10) to implement the first stage of isochoric combustion. The electronic control module (13) is also used to control the second fuel injector to inject the second fuel into the target high-temperature reaction area after the first stage of combustion reaches the predetermined combustion progress, forming a local fuel-rich core and an outer oxidation envelope area, and to make the second stage of combustion form a quasi-isobaric exothermic reaction by controlling the second fuel injection rate.

2. The staged fuel supply system according to claim 1, characterized in that, The first fuel supply module (8) and the second fuel supply module (11) supply the same fuel in stages, or two fuels with different chemical compositions; the first fuel supply module (8) is a lean premixed gas or volatile liquid fuel, and the second fuel supply module (11) is a gas or liquid fuel that can be directly injected into the cylinder to form a local fuel-rich zone.

3. The staged fuel supply system according to claim 2, characterized in that, The first fuel supply module (8) and the second fuel supply module (11) include at least one of natural gas, methane, hydrogen, ammonia, methanol, ethanol, dimethyl ether, gasoline, diesel, biofuel, synthetic fuel and mixtures thereof.

4. The staged fuel supply system according to claim 1, characterized in that, The second fuel supply module (11) is implemented by at least one of single injection, main injection plus supplementary injection, segmented injection or injection rate shaping, in order to match the second stage heat release rate with the pressure drop rate caused by piston expansion.

5. The staged fuel supply system according to claim 1, characterized in that, The second fuel injector is mounted on the cylinder head, cylinder sidewall, or pre-combustion chamber body, and the second fuel injector is provided with one or more injection holes.

6. The staged fuel supply system according to claim 1, characterized in that, The combustion progress in the first stage is determined by at least one of CA10, CA50, cumulative heat release ratio, in-cylinder pressure rise rate, and the time when the flame reaches the calibrated position; the quasi-isobaric heat release determination criteria for the second stage are that the deviation of the in-cylinder pressure from the target pressure does not exceed the calibrated value, or the absolute value of the pressure change rate per unit crankshaft angle does not exceed the calibrated value.

7. A staged fuel injection control method, characterized in that, The method is implemented based on the staged fuel supply system of claim 1, and the method includes the following steps: Step 1: Control the first fuel supply module (8) to deliver the first fuel, form a lean mixture with a global excess air coefficient greater than 1 and ignite it, and complete the first stage of combustion near the top dead center with approximately equal volume. Step 2: Collect in-cylinder combustion feedback signals, and after determining that the first stage of combustion has reached the predetermined progress, control the second fuel injector to inject the second fuel into the target high-temperature reaction area in the cylinder to form a local fuel-rich core and an outer oxidation envelope area. Step 3: Adjust the timing, rate, and quantity of the second fuel injection to ensure that the second stage releases heat at near-isobaric pressure in the early stage of expansion, and that the overall excess air coefficient of the cylinder remains greater than 1 throughout the entire process. Step 4: Adjust the fuel supply parameters for the two stages of the subsequent cycle based on real-time cylinder pressure, cycle fluctuation, and exhaust component data; Step 5: Monitor the operation of the supply system and engine body (1) in real time. If any abnormality occurs, adjust or cut off the second fuel supply in stages.

8. The staged fuel injection control method according to claim 7, characterized in that, In step 1, the first stage of combustion is approximately isochoric heat release through lean premixing, and the second stage is approximately isobaric heat release through fuel-rich combustion.

9. The staged fuel injection control method according to claim 7, characterized in that, The target high-temperature reaction zone mentioned in step 2 includes at least one of the following: the already burned high-temperature zone formed by the first stage combustion, the region behind the flame front, the wake region of the first fuel jet, the high-temperature zone formed by the ignition jet, and the region where the temperature, oxygen concentration, and remaining reaction time meet the requirements of the second fuel conversion.

10. The staged fuel injection control method according to claim 7, characterized in that, The engine described in step 5 uses a higher geometric compression ratio than the benchmark engine, and uses the Miller cycle to make the effective compression ratio lower than the geometric compression ratio.

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