Diesel and ammonia dual-fuel engine and method for reforming mixture activity and efficient combustion

Abstract

The object of the present invention is to provide a diesel and ammonia dual-fuel engine and a method for reforming the activity of the mixture and efficient combustion, including a piston, a cylinder, an exhaust passage, an in-cylinder direct injection ammonia injector, an exhaust valve, a cylinder head, a high-pressure common rail fuel injector, an intake valve, an intake passage, a cylinder pressure sensor, and an ECU. The high-pressure common rail fuel injector and the high-pressure common rail ammonia injector with a single common rail are used for in-cylinder direct injection to achieve the dual-fuel supply of ammonia and diesel, and the fuel supply is controlled to achieve the stratification of fuel concentration and reactivity and multi-mode combustion. The exhaust valve is closed in advance through a variable valve train to change the amount of residual exhaust gas in the cylinder to achieve exhaust gas trapping, and a small amount of diesel is injected at the end of the exhaust stage, and fuel reforming is achieved by using the high-temperature exhaust gas in the cylinder. The present invention adopts means such as in-cylinder exhaust gas trapping by a variable valve train, fuel reforming, and coordinating fuel injection pulse width and timing to flexibly control the combustion mode under different operating conditions, so as to achieve high efficiency and low emissions under all operating conditions of the engine.

Description

Technical Field

[0001] The present invention relates to an engine and a combustion method, specifically a dual-fuel engine and a combustion method. Background Art

[0002] Compared with typical hydrocarbon fuels, ammonia emits only water and nitrogen when completely burned in oxygen. However, in practical applications, it is very difficult to achieve complete combustion of ammonia fuel in an internal combustion engine. And compared with conventional hydrocarbon fuels, the laminar burning velocity and calorific value of pure ammonia are relatively low, and the energy required for ignition is relatively high, and the flammability limit range is relatively narrow, making the combustion of pure ammonia more difficult. Therefore, it is necessary to modify or redesign the traditional combustion system so as to be able to apply ammonia reliably, safely and cleanly.

[0003] In terms of ammonia combustion, blending ammonia with other combustion improvers for combustion has always been an important development direction. Since the combustion velocity of hydrogen is very fast, trying to add hydrogen to ammonia is a better choice to improve the combustion velocity of ammonia fuel. However, pure hydrogen is difficult to promote due to problems such as storage and transportation. Patent CN114294129A mentions a hydrogen jet ignition combustion system for an ammonia engine, which ignites hydrogen in a pre-chamber and uses the hydrogen jet to ignite ammonia in the main combustion chamber. However, the requirements for the combustion system for igniting hydrogen in the pre-chamber and the hydrogen jet are high and the reliability is poor. Patent CN114483299A mentions a system and method for reducing unburned ammonia emissions in an ammonia engine, which uses the waste heat of the engine exhaust gas to displace hydrogen and reuses the residual ammonia in the tail gas, achieving the purpose of energy conservation and emission reduction. However, the ammonia cracking temperature is relatively high and the ammonia content in the tail gas is low, making it difficult to meet the engine's demand for hydrogen. Summary of the Invention

[0004] The purpose of the present invention is to provide a diesel and ammonia dual-fuel engine and a method for reforming the activity of the mixture and efficient combustion, which can solve the problems of carbon oxide and sulfur oxide emissions caused by the combustion of fossil fuels in traditional engines, and at the same time reduce the nitrogen oxide emissions caused by fuel combustion.

[0005] The purpose of the present invention is achieved as follows:

[0006] The diesel and ammonia dual-fuel engine of the present invention is characterized in that it includes a cylinder, a fuel supply device, an ammonia supply device, a high-pressure fuel rail, a liquid ammonia rail, an intake valve, an exhaust valve, and an ECU. The cylinder includes a cylinder liner, a cylinder head, and a piston. A high-pressure common rail injector and an in-cylinder direct injection ammonia injector are arranged on the cylinder head. The axis of the high-pressure common rail injector coincides with the axis of the cylinder. The in-cylinder direct injection ammonia injector is inclined. The axis of the in-cylinder direct injection ammonia injector and the axis of the cylinder are in the same spatial plane. The fuel supply device is connected to the high-pressure common rail injector through the high-pressure fuel rail. The ammonia supply device is connected to the in-cylinder direct injection ammonia injector through the liquid ammonia rail. The cylinder is connected to the intake passage through the intake valve and to the exhaust passage through the exhaust valve. A cylinder pressure sensor is arranged on the cylinder head and is connected to the ECU. The spray holes of the in-cylinder direct injection ammonia injector adopt an asymmetric design. The intersection points of the axial extension lines of the spray holes and the piston surface are in the same plane. At the same time, the spray holes near the cylinder axis adopt a larger spray hole diameter, so that the liquid ammonia injected by the in-cylinder direct injection ammonia injector is evenly distributed. The central axis of the in-cylinder direct injection ammonia injector intersects with the central axis of the high-pressure common rail injector, so that the liquid ammonia injected by the in-cylinder direct injection ammonia injector is distributed on the oil spray path of the high-pressure common rail injector.

[0007] The diesel and ammonia dual-fuel engine and the method for reforming the activity and efficient combustion of the mixture gas of the present invention are characterized in that it includes a method for realizing fuel reforming, specifically: at the end of the exhaust stroke, the exhaust valve is closed before the top dead center to seal the cylinder, and the piston continues to move to compress the exhaust gas in the cylinder, increasing the pressure and temperature in the cylinder. The high-pressure common rail injector injects a small amount of diesel into the cylinder, and the high-temperature environment provided by the high-temperature exhaust gas remaining in the cylinder is used to cause the diesel to reform, generating highly reactive substances to promote the subsequent fuel combustion.

[0008] The diesel and ammonia dual-fuel engine and the method for reforming the activity and efficient combustion of the mixture gas of the present invention may further include:

[0009] 1. It includes a method for realizing exhaust gas capture, specifically: at the end of the exhaust stroke, the ECU controls the exhaust valve to close in advance to leave the high-temperature exhaust gas in the cylinder. At the same time, the ECU judges the remaining amount of exhaust gas and adjusts the remaining amount of exhaust gas by controlling the closing moment of the exhaust valve. The hydrogen and other reactive substances generated by fuel reforming are mixed with air and ammonia respectively in the subsequent intake and compression stages, improving the overall reaction activity in the cylinder, accelerating the fuel reaction speed, and shortening the ignition delay period.

[0010] 2. It includes a pure diesel operation mode: during starting and idling conditions, the in-cylinder direct injection ammonia injector is closed, and the high-pressure common rail injector injects diesel once at the end of the compression stage for combustion. For low-load, medium-load, and high-load conditions, the pure diesel operation mode is used as a backup fuel supply mode and is switched with other operation modes when needed to meet the engine operation requirements. Before the top dead center of compression, the high-pressure common rail injector injects a large amount of diesel once for combustion.

[0011] 3. It includes a diesel / ammonia dual-fuel operation mode: diesel is injected by a high-pressure common rail injector, and liquid ammonia is injected by an in-cylinder direct injection ammonia injector. The injection ratio of diesel and liquid ammonia is adjusted according to the load. The ECU controls the opening and closing times of the exhaust valve according to the load change to achieve exhaust trapping and fuel reforming.

[0012] When the engine is operating under high-load conditions, exhaust trapping and fuel reforming are not used; ammonia is used as the main fuel and diesel as the pilot fuel; the closing time of the intake valve is delayed, so that the actual compression ratio of the engine is less than the expansion ratio to suppress knocking; after the intake valve is closed, the in-cylinder direct injection ammonia injector injects low-pressure liquid ammonia into the cylinder to form a liquid ammonia spray. The liquid ammonia spray evaporates after entering the cylinder, and ammonia mixes with the intake air during the compression process to form a homogeneous mixture, avoiding local fuel concentration leading to too high combustion temperature; when the piston moves to near the top dead center during the compression stage, the high-pressure common rail injector injects diesel into the cylinder, and the ammonia fuel is ignited by the diesel combustion.

[0013] When the engine is operating under medium and low load conditions, the proportion of diesel in the fuel increases and the proportion of ammonia in the fuel decreases; at the end of the exhaust stage, the ECU controls the opening and closing times of the exhaust valve according to the load change and the signal of the cylinder pressure sensor, and uses the heating effect of the residual high-temperature exhaust gas to enhance the reaction activity of the in-cylinder mixture and expand the engine power range; the high-pressure common rail injector injects a small amount of diesel for fuel reforming after the exhaust valve is closed and before the top dead center of compression to generate highly active free radicals and enhance the overall reaction activity of the mixture in the cylinder; when the piston moves near the top dead center, the high-pressure common rail injector injects the main diesel into the cylinder to form multiple ignition sources. After the start of the main injection of diesel, the in-cylinder direct injection ammonia injector injects high-pressure liquid ammonia into each ignition source in the cylinder. The liquid ammonia evaporates after injection, forms a locally rich mixture near the high-pressure common rail injector, and is ignited by the diesel. After the end of the main injection of diesel, post-injection of diesel is carried out to burn out the unburned ammonia.

[0014] The advantages of the present invention are as follows:

[0015] 1. The injection states of the high-pressure common rail injector and the in-cylinder direct injection ammonia injector are flexibly controlled according to the load change to achieve the switching and backup of the dual-fuel mode and the pure diesel mode. Especially under transitional conditions, diesel and ammonia are coupled and injected multiple times to meet the requirements of transient conditions and emission regulations, ensuring coverage of the entire working range of the engine and the reliability of operation.

[0016] 2. By changing the closing time of the intake valve to the initial stage of the compression stage, the Miller cycle is simply and conveniently realized, which can reduce the compression work, improve the thermal efficiency, reduce the fuel consumption rate, effectively suppress knocking of the engine under high load, and also reduce the in-cylinder combustion temperature, reduce the thermal load, and reduce NOx emissions.

[0017] 3. By controlling the early closing of the exhaust valve through a variable valve timing system, the amount of exhaust gas remaining in the cylinder is controlled to achieve exhaust gas trapping. At the end of the exhaust stage, a small amount of diesel is injected into the cylinder by a high-pressure common rail injector. The diesel undergoes fuel reforming in the high-temperature exhaust gas to generate hydrogen and other active substances. In the next working cycle of the engine, the hydrogen and other active substances can increase the reaction activity of ammonia, thereby increasing the flame propagation speed, shortening the ignition delay period, significantly improving in-cylinder combustion, and increasing the overall engine thermal efficiency.

[0018] 4. At the beginning of the intake stage, the high-temperature exhaust gas remaining in the cylinder can increase the initial cylinder temperature and accelerate the evaporation rate of the low-pressure injected liquid ammonia, which is beneficial to the mixing of ammonia and the in-cylinder gas.

[0019] 5. The fuel supply method of in-cylinder direct injection enables the engine to be designed with a larger valve overlap angle to enhance the scavenging effect. At the same time, in-cylinder direct injection can implement more injection schemes for ammonia and diesel, which is beneficial to the flexible setting of injection timing to meet the requirements of different working conditions.

[0020] 6. Supplying ammonia by in-cylinder direct injection can effectively prevent the evaporation gas of liquid ammonia from leaking out of the cylinder.

[0021] 7. The present invention is applicable not only to Miller cycle engines but also to other compression ignition engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic structural diagram of the present invention;

[0023] Figure 2 is a connection diagram of the ECU;

[0024] Figure 3 is a bottom view of the in-cylinder state at the end of the compression stage in the medium and high load conditions of the combustion system in ammonia / diesel dual fuel mode;

[0025] Figure 4 is a diagram of the intake and exhaust timing of the combustion system;

[0026] Figure 5 is a diagram of the cylinder pressure change. DETAILED DESCRIPTION OF THE INVENTION

[0027] The present invention will be described in more detail with reference to the accompanying drawings as follows:

[0028] Combined with Figures 1-5, the diesel / ammonia dual-fuel engine of the present invention includes a piston 1, a cylinder liner 2, an exhaust passage 3, an in-cylinder direct injection ammonia injector 3, an exhaust valve 5, a cylinder head 6, a common rail fuel injector 7, an intake valve 8, an intake passage 9, an ammonia rail 10, a high-pressure fuel rail 11, a fuel supply device 12, an ammonia supply device 13, an ECU 14, and a cylinder pressure sensor 15. A common rail fuel injector 7 and an in-cylinder direct injection ammonia injector 4 are installed on the cylinder head 6; the axis of the common rail fuel injector 7 coincides with the axis of the cylinder 2; the in-cylinder direct injection ammonia injector 4 is inclined and arranged on the cylinder head 6, and the axis of the in-cylinder direct injection ammonia injector 4 and the axis of the cylinder 2 are in the same spatial plane; the cylinder pressure sensor 15 is arranged on the cylinder head 6 of one of the cylinders 2 of the engine; the ECU 14 receives signals including the cylinder pressure sensor 15 and controls components including the in-cylinder direct injection ammonia injector 3, the exhaust valve 5, the common rail fuel injector 7, and the intake valve 8.

[0029] Combined Figure 3 , the nozzle holes of the in-cylinder direct injection ammonia injector 4 adopt an asymmetric design, and the intersection points of the axial extension lines of the nozzle holes and the surface of the piston 1 are on the same plane. At the same time, the nozzle holes near the axis of the cylinder 2 adopt a larger nozzle hole diameter, so that the liquid ammonia injected by the in-cylinder direct injection ammonia injector 4 is evenly distributed; the central axis of the in-cylinder direct injection ammonia injector 4 intersects with the central axis of the common rail fuel injector 7, so that the liquid ammonia injected by the in-cylinder direct injection ammonia injector 4 is distributed on the oil spray path of the common rail fuel injector 7.

[0030] Combined Figure 4 and Figure 5 , the ECU 14 judges the residual amount of exhaust gas in the cylinder 2 by receiving the signal of the cylinder pressure sensor 15, and uses the residual amount of exhaust gas in the cylinder 2 as a basis to control the residual amount of exhaust gas in each cylinder 2 of the engine, thereby calculating the in-cylinder EGR rate. The method for realizing fuel reforming is as follows: at the end of the exhaust stroke, the exhaust valve 5 is closed before the top dead center to seal the cylinder 2, and the piston 1 continues to move to compress the exhaust gas in the cylinder, increasing the pressure and temperature in the cylinder 2; the common rail fuel injector 7 injects a small amount of diesel into the cylinder 2, and the high-temperature environment provided by the high-temperature exhaust gas remaining in the cylinder is used to cause the diesel to reform, generating highly reactive substances for promoting subsequent fuel combustion. The method for realizing exhaust gas capture is as follows: at the end of the exhaust stroke, the ECU 14 controls the exhaust valve 5 to close in advance to leave high-temperature exhaust gas in the cylinder 2. At the same time, the ECU 14 judges the residual amount of exhaust gas and adjusts the residual amount of exhaust gas by controlling the closing time of the exhaust valve 5. The hydrogen and other reactive substances generated by fuel reforming are mixed with air and ammonia respectively in the subsequent intake and compression stages, improving the overall reaction activity in the cylinder, accelerating the fuel reaction speed, and shortening the ignition delay period.

[0031] By using a variable valve timing system to delay the closing time of the intake valve 8 to the initial stage of the compression stroke, the Miller cycle is achieved, that is, the actual compression ratio during the intake stroke of the engine is less than the expansion ratio during the power stroke. This can reduce the compression work, improve the thermal efficiency, reduce the fuel consumption rate, effectively suppress engine knocking, and lower the in-cylinder temperature, thereby inhibiting the generation of NOx.

[0032] The engine uses in-cylinder direct injection to supply diesel and ammonia. Different injection modes can be achieved by changing the injection states of the high-pressure common rail injector 7 and the in-cylinder direct injection ammonia injector 4, including the pure diesel mode and the ammonia / diesel dual-fuel mode. The injection states include the injection times and injection timings. The injection states of the high-pressure common rail injector 7 and the in-cylinder direct injection ammonia injector 4 are flexibly controlled according to the load change to achieve the switching and backup between the dual-fuel mode and the pure diesel mode. Especially under transient conditions, diesel and ammonia are coupled for multiple injections to meet the requirements of transient conditions and emission regulations, ensuring coverage of the entire operating range of the engine and the reliability of operation.

[0033] The high-pressure common rail injector 7 is a single common rail orifice-type high-pressure common rail injector, which can achieve single and multiple injections within one cycle and adjust the injection times, injection quantities, and injection timings according to actual needs. The in-cylinder direct injection ammonia injector 4 is a variable rail pressure liquid ammonia injector, which can achieve high-pressure injection of liquid ammonia and low-pressure injection of liquid ammonia, and adjust the injection pressure, injection times, and injection quantities according to actual needs. The low-pressure injection of liquid ammonia occurs after the exhaust valve 5 closes and during the intake period. At the initial stage of the intake stroke, the remaining high-temperature exhaust gas in the cylinder can increase the initial in-cylinder temperature. At this time, when the low-pressure liquid ammonia spray enters the cylinder, it evaporates rapidly, and under the action of in-cylinder turbulence, the evaporated gas mixes fully with the in-cylinder air to form a mixture of ammonia and air. The high-pressure injection of liquid ammonia occurs near the top dead center, with the same injection timing as diesel. Diesel, as a highly reactive fuel, starts to burn rapidly after injection, while the high-pressure liquid ammonia spray, as a low-reactive fuel, is ignited by the diesel combustion flame.

[0034] In the pure diesel operation mode, during starting and idling conditions, due to the low temperature of the engine components and the low temperature at the end of the in-cylinder compression, and the ignition point of diesel (527K) being much lower than that of ammonia (930K), diesel is selected to reduce the occurrence of incomplete combustion or misfire. The in-cylinder direct injection ammonia injector 4 is closed, and the high-pressure common rail injector 7 injects diesel once at the end of the compression stroke for combustion; for low-load, medium-load, and high-load conditions, the pure diesel operation mode serves as a backup fuel supply mode and can be switched to the diesel / ammonia dual-fuel operation mode when needed to meet the engine operation requirements. Before the compression top dead center, the high-pressure common rail injector 7 injects a large amount of diesel once for combustion.

[0035] In the diesel / ammonia dual-fuel operation mode, diesel is injected by the high-pressure common rail injector 7, and liquid ammonia is injected by the in-cylinder direct injection ammonia injector 4. The injection ratio of diesel and liquid ammonia is adjusted according to the load. The ECU 14 controls the opening and closing times of the exhaust valve 5 according to the load change to achieve exhaust trapping and fuel reforming. When the engine operates at high load conditions, exhaust trapping and fuel reforming are not used; ammonia is used as the main fuel and diesel is used as the pilot fuel; the closing time of the intake valve 8 is postponed, so that the actual compression ratio of the engine is less than the expansion ratio to suppress knocking; after the intake valve 8 is closed, the in-cylinder direct injection ammonia injector 4 injects low-pressure liquid ammonia into the cylinder to form a liquid ammonia spray. The liquid ammonia spray evaporates rapidly after entering the cylinder, reducing the temperature of the in-cylinder mixture. During the compression process, ammonia is mixed with the intake air to form a homogeneous mixture to avoid local fuel enrichment leading to too high combustion temperature; when the piston moves to near the top dead center during the compression stage, the high-pressure common rail injector 7 injects diesel into the cylinder, and the ammonia fuel is ignited by the combustion of diesel. When the engine operates at medium and low load conditions, the proportion of diesel in the fuel increases and the proportion of ammonia in the fuel decreases; at the end of the exhaust stage, the ECU 14 controls the opening and closing times of the exhaust valve 5 according to the load change and the signal of the cylinder pressure sensor 15 to accurately control the amount of exhaust gas trapped by exhaust trapping. Using the heating effect of the residual high-temperature exhaust gas, the reaction activity of the in-cylinder mixture is improved and the engine power range is extended; the high-pressure common rail injector 7 injects a small amount of diesel for fuel reforming after the exhaust valve 5 is closed and before the top dead center of compression to generate a certain amount of highly reactive free radicals to improve the overall reaction activity of the mixture in the cylinder; when the piston 1 moves to near the top dead center, the high-pressure common rail injector 7 injects the main diesel injection into the cylinder to form multiple ignition sources. After the main diesel injection starts, the in-cylinder direct injection ammonia injector 4 injects high-pressure liquid ammonia to each ignition source in the cylinder. The liquid ammonia evaporates rapidly after injection, forming a locally rich mixture near the high-pressure common rail injector 7 and being ignited by diesel. After the main diesel injection ends, post-injection of diesel is carried out to burn out the unburned ammonia.

Claims

1. Method for reforming the activity of the mixture and efficient combustion of a diesel and ammonia dual-fuel engine, Characterized in that: The diesel and ammonia dual-fuel engine includes a cylinder, a fuel supply device, an ammonia supply device, a high-pressure fuel rail, a liquid ammonia rail, an intake valve, an exhaust valve, and an ECU. The cylinder includes a cylinder liner, a cylinder head, and a piston. A high-pressure common rail injector and an in-cylinder direct injection ammonia injector are arranged on the cylinder head. The axis of the high-pressure common rail injector coincides with the axis of the cylinder; the in-cylinder direct injection ammonia injector is arranged obliquely, and the axis of the in-cylinder direct injection ammonia injector and the axis of the cylinder are in the same spatial plane. The fuel supply device is connected to the high-pressure common rail injector through the high-pressure fuel rail, and the ammonia supply device is connected to the in-cylinder direct injection ammonia injector through the liquid ammonia rail. The cylinder is connected to the intake passage through the intake valve and to the exhaust passage through the exhaust valve. A cylinder pressure sensor is arranged on the cylinder head, and the cylinder pressure sensor is connected to the ECU. The spray holes of the in-cylinder direct injection ammonia injector adopt an asymmetric design, and the intersection points of the axial extension lines of the spray holes and the piston surface are in the same plane. At the same time, the spray holes near the cylinder axis adopt a larger spray hole diameter, so that the liquid ammonia sprayed by the in-cylinder direct injection ammonia injector is evenly distributed; the central axis of the in-cylinder direct injection ammonia injector intersects with the central axis of the high-pressure common rail injector, so that the liquid ammonia sprayed by the in-cylinder direct injection ammonia injector is distributed on the oil spray path sprayed by the high-pressure common rail injector; The method includes a fuel reforming implementation method, specifically: at the end of the exhaust stroke, the exhaust valve closes before top dead center to seal the cylinder, and the piston continues to move to compress the exhaust gas in the cylinder, increasing the pressure and temperature in the cylinder; the high-pressure common rail injector sprays a small amount of diesel into the cylinder, and uses the high-temperature environment provided by the high-temperature exhaust gas remaining in the cylinder to cause the diesel to reform, generating highly reactive substances to promote subsequent fuel combustion; it also includes an exhaust gas capture implementation method, specifically: at the end of the exhaust stroke, the ECU controls the exhaust valve to close in advance to leave the high-temperature exhaust gas in the cylinder. At the same time, the ECU judges the residual amount of the exhaust gas and adjusts the residual amount of the exhaust gas by controlling the closing time of the exhaust valve. The hydrogen and other reactive substances generated by the fuel reforming are mixed with air and ammonia respectively in the subsequent intake and compression stages, improving the overall reaction activity in the cylinder, accelerating the fuel reaction speed, and shortening the ignition delay period.

2. The method for reforming the activity of the mixture and efficient combustion of a diesel and ammonia dual-fuel engine according to claim 1, Characterized in that: It includes a pure diesel operation mode: during starting and idling conditions, the in-cylinder direct injection ammonia injector is closed, and the high-pressure common rail injector injects diesel once at the end of the compression stage for combustion; for low-load, medium-load, and high-load conditions, the pure diesel operation mode is used as a standby fuel supply mode and can be switched to other operation modes when needed to meet the engine operation requirements. Before top dead center of compression, the high-pressure common rail injector injects a large amount of diesel once for combustion.

3. The method for reforming the activity of the mixture and efficient combustion of a diesel and ammonia dual-fuel engine according to claim 1, Characterized in that: It includes a diesel / ammonia dual-fuel operation mode: diesel is injected by a high-pressure common rail injector, and liquid ammonia is injected by an in-cylinder direct injection ammonia injector. The injection ratio of diesel and liquid ammonia is adjusted according to the load, and the ECU controls the opening and closing moments of the exhaust valve according to the load change to achieve exhaust trapping and fuel reforming; When the engine operates under high load conditions, exhaust trapping and fuel reforming are not used; ammonia is used as the main fuel and diesel is used as the pilot fuel; the closing moment of the intake valve is delayed, so that the actual compression ratio of the engine is less than the expansion ratio to suppress knocking; after the intake valve is closed, the in-cylinder direct injection ammonia injector injects low-pressure liquid ammonia into the cylinder to form a liquid ammonia spray. The liquid ammonia spray evaporates after entering the cylinder, and ammonia mixes with the intake air during the compression process to form a homogeneous mixture, avoiding excessive local fuel concentration leading to too high combustion temperature; when the piston moves to near the top dead center during the compression stage, the high-pressure common rail injector injects diesel into the cylinder, and the ammonia fuel is ignited by the combustion of diesel; When the engine operates under medium and low load conditions, the proportion of diesel in the fuel increases and the proportion of ammonia in the fuel decreases; at the end of the exhaust stage, the ECU controls the opening and closing moments of the exhaust valve according to the load change and the signal of the cylinder pressure sensor, and uses the heating effect of the residual high-temperature exhaust gas to improve the reaction activity of the in-cylinder mixture and expand the engine power range; the high-pressure common rail injector injects a small amount of diesel for fuel reforming after the exhaust valve is closed and before the top dead center of compression to generate highly reactive free radicals and improve the overall reaction activity of the mixture in the cylinder; when the piston moves near the top dead center, the high-pressure common rail injector injects the main diesel injection into the cylinder to form multiple ignition sources. After the start of the main diesel injection, the in-cylinder direct injection ammonia injector injects high-pressure liquid ammonia into each ignition source in the cylinder. The liquid ammonia evaporates after injection, forms a locally rich mixture near the high-pressure common rail injector, and is ignited by diesel. After the end of the main diesel injection, after-injection of diesel is carried out to burn out the unburned ammonia.

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