Ammonia hydrogen fuel engine based on liquid ammonia thermal management supply system and operation control method

Abstract

The purpose of the present invention is to provide an ammonia hydrogen fuel engine and operation control method based on a liquid ammonia thermal management supply system, including a multi-stage heat recovery unit, a cooling unit, and an ammonia hydrogen fuel internal combustion engine. When the engine is started, the thermal cracker is not working at this time, and the liquid ammonia enters the combustion chamber through direct injection into the cylinder. A small amount of hydrogen in the hydrogen storage tank is supplied to the pre-combustion chamber and the intake duct to assist the initial combustion of ammonia. The hydrogen in the pre-combustion chamber is ignited by a spark plug to achieve ignition of ammonia. After starting, the high-temperature exhaust gas is subjected to multi-stage heat recovery for shaft work compensation. In addition, the heat recovery unit is used to achieve ammonia overheating control and energy supply to the SCR reductant and cracker. The hydrogen mixture can also be pre-mixed with the refluxed ammonia for intake supply. Through the fuel supply and management system, the efficient combustion of ammonia fuel and the efficient operation of the ammonia hydrogen fuel engine are achieved from the perspective of fuel combustion, solving the problem of low thermal efficiency of the ammonia fuel engine caused by the inherent properties of ammonia fuel.

Description

Technical Field

[0001] The present invention relates to a new energy engine, specifically an ammonia hydrogen fuel engine and an operation control method. Background Art

[0002] Ammonia is considered to be an ideal fuel for power systems to meet the "dual carbon" goals, but it has combustion problems such as high ignition point, low calorific value, and slow flame propagation speed, while hydrogen has the advantages of low ignition energy, high combustion temperature, and fast flame propagation speed. Therefore, ammonia-hydrogen engines with hydrogen as ignition fuel have also become one of the advanced core technologies for achieving the near-zero emission goals of power systems. Although ammonia-hydrogen engines using clean fuels have practical significance for zero carbon emissions, the inherent properties of ammonia fuel are an inevitable problem as a fuel. The resulting thermal efficiency of ammonia fuel engines and the post-treatment of incomplete combustion products pose many challenges to the application of ammonia fuel engines. Therefore, it is necessary to design a more comprehensive and efficient fuel supply and waste heat utilization technology to match the zero-carbon engine, achieve zero carbon emissions in the system, improve the combustion characteristics of ammonia fuel, and achieve efficient use of heat through waste heat utilization. Summary of the invention

[0003] The object of the present invention is to provide an ammonia-hydrogen fuel engine and an operation control method based on a liquid ammonia thermal management supply system that can solve the problems of low energy efficiency of ammonia fuel engines and poor combustion effect of ammonia fuel.

[0004] The object of the present invention is achieved in that:

[0005] The invention is based on an ammonia hydrogen fuel engine of a liquid ammonia thermal management supply system, which is characterized by comprising an ammonia hydrogen fuel engine, a heat recovery unit, a cooling unit, and a turbocharger, wherein the turbocharger is connected between the ammonia hydrogen fuel engine and the heat recovery unit, the ammonia hydrogen fuel engine comprises an ammonia storage tank, a hydrogen storage tank, an ammonia fuel common rail pipe, an engine body, an ammonia return control valve group, and a mixer, the ammonia storage tank is connected to the ammonia fuel common rail pipe, the hydrogen storage tank is connected to the hydrogen gas rail through a hydrogen buffer tank, a cylinder, an ammonia fuel injector, and an active pre-combustion chamber are respectively arranged in the engine body, and the ammonia fuel injector and the active pre-combustion chamber are separately arranged. The ammonia fuel common rail is connected to the ammonia fuel injector, and the hydrogen gas rail is connected to the active pre-combustion chamber. The ammonia return control valve group includes a first to a third electronic expansion valve. The first electronic expansion valve is connected to the third electronic expansion valve in parallel and is connected to the second electronic expansion valve. The first electronic expansion valve and the third electronic expansion valve are respectively connected to the first electromagnetic three-way valve, and the first electromagnetic three-way valve is connected to the ammonia storage tank through the ammonia buffer tank. The first electronic expansion valve is also connected to the ammonia fuel injector, and the third electronic expansion valve is also connected to the mixer. The mixer is respectively connected to the turbocharger and the pipeline between the hydrogen buffer tank and the hydrogen gas rail.

[0006] The ammonia-hydrogen fuel engine based on the liquid ammonia thermal management supply system of the present invention may also include:

[0007] 1. The heat recovery unit includes an SCR post-processing device, a turbine, a steam turbine, and a thermal cracker. The waste heat discharged from the exhaust gas turbocharger enters the SCR post-processing device for discharge after heat exchange in the second heat exchanger. Ammonia absorbs heat at the second heat exchanger and changes from liquid to ammonia vapor, and enters the turbine to expand and convert into mechanical energy output. The ammonia entering the heat recovery unit absorbs the exhaust gas in the third heat exchanger for superheating and becomes gaseous ammonia. After that, it enters the thermal cracker through a three-way valve to decompose the ammonia into nitrogen and hydrogen. The hydrogen enters the hydrogen storage tank as ignition fuel, and enters the SCR post-processing device through a three-way valve on the other hand. The exhaust gas generated from the cracker is converted into shaft power by a turbine coaxial with the steam turbine and then discharged.

[0008] 2. The cooling unit includes a first radiator, a second radiator, a lubricating oil tank, a water tank, a cooling water pump, and a lubricating oil pump. The two ends of the first radiator are respectively connected to the water tank and the cooling water pump, the water tank is connected to the engine cooling water inlet, and the cooling water pump is connected to the engine cooling water outlet. The two ends of the second radiator are respectively connected to the lubricating oil tank and the lubricating oil pump, and the lubricating oil tank and the lubricating oil pump are both connected to the ammonia hydrogen fuel engine.

[0009] The present invention provides an operation control method for an ammonia hydrogen fuel engine based on a liquid ammonia thermal management supply system, which is characterized in that: when the engine is started, the liquid ammonia supply unit supplies liquid ammonia fuel to the ammonia fuel common rail and the ammonia fuel in-cylinder direct injection device, and the hydrogen fuel is used as the ignition and combustion-supporting fuel of the ammonia fuel. At this time, the ammonia fuel cracker is not running, and the hydrogen fuel is operated through the hydrogen stored in the hydrogen storage tank. A part of the hydrogen fuel is supplied to the in-cylinder injection device, and after ignition, the jet ignites the ammonia fuel injected into the cylinder, and the other part enters the combustion chamber through the intake duct to support combustion.

[0010] The operation control method of the ammonia-hydrogen fuel engine based on the liquid ammonia thermal management supply system of the present invention may also include:

[0011] 1. When the engine is running, the liquid ammonia supplied by the liquid ammonia supply component enters the cylinder injection device after completing the overheat control, and the other part of the ammonia fuel is gasified into ammonia and enters the multi-stage heat recovery component, the ammonia cracker and the SCR post-treatment device. The exhaust heat energy of the internal combustion engine provides energy for the ammonia cracking reaction in the ammonia cracker and the SCR post-treatment device. During the operation, the ammonia cracker works, and the hydrogen generated after the ammonia cracking reaction meets the needs of the internal combustion engine. At the same time, the additional exhaust gas is compensated for the shaft work through the turbine. If the hydrogen fuel meets the use requirements at this time, the liquid ammonia supply component stops supplying, and the fuel cylinder injection device injects the hydrogen, ammonia and nitrogen mixed gas generated after the ammonia cracking reaction from the hydrogen storage tank into the cylinder of the ammonia hydrogen internal combustion engine, and at the same time enters the combustion chamber through the mixer of the intake duct as ammonia combustion-supporting fuel.

[0012] The advantages of the present invention are:

[0013] 1. The present invention realizes the efficient coupling of waste heat utilization of ammonia hydrogen engine, fully utilizes the waste heat energy of the engine, improves the energy utilization efficiency and realizes the carbon-free emission of the system.

[0014] 2. The present invention adopts liquid supply of ammonia fuel and direct injection into the cylinder for supply and injection. At the same time, through the control of the return ammonia, the coupling of two injection modes supplemented by intake duct injection is realized, and the ignition and combustion-supporting functions of hydrogen fuel are combined to enhance the combustion in the engine cylinder and realize an adjustable injection mode under multiple working conditions.

[0015] 3. Through the heat recovery unit, the ammonia hydrogen fuel engine supply system is overheated to solve the inherent property defects of ammonia fuel, such as slow combustion speed and high ignition point, to increase the combustion speed and thermal efficiency, and to meet the various injection requirements of the engine.

[0016] 4. The engine waste heat is recovered and utilized in multiple stages through the heat recovery unit to achieve engine waste heat shaft work compensation and multi-stage overheating of ammonia to meet the energy requirements of the thermal cracker and SCR post-treatment device.

[0017] 5. Compared with other zero-carbon power units, the engine can use low-purity hydrogen fuel. The engine's online hydrogen production design can improve the engine's integration level and improve engine operation safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the present invention;

[0019] Figure 2 This is a schematic diagram of the structure of the ammonia hydrogen fuel supply system;

[0020] Figure 3 This is a schematic diagram of the valve group structure of the ammonia return control unit;

[0021] Figure 4 is a schematic diagram of the heat recovery unit structure;

[0022] Figure 5 is a schematic diagram of the cooling unit structure;

[0023] Figure 6 The present invention is a control flow chart of the operation control method of an ammonia-hydrogen fuel engine. DETAILED DESCRIPTION

[0024] The present invention is described in more detail below with reference to the accompanying drawings:

[0025] Combination Figure 1-6 , Figure 1This is a schematic diagram of the overall structure of the present invention. The ammonia-hydrogen fuel engine based on the liquid ammonia thermal management supply system includes an ammonia-hydrogen fuel engine 3, a heat recovery unit 6, a cooling unit 8, an exhaust gas turbocharger 1, exhaust ports 4 and 5, an intercooler 2, intercooler ports 9 and 10, an ammonia supply pump 7, and a number of pipelines. One path of the exhaust gas and waste heat discharged from the ammonia-hydrogen fuel engine system 3 enters the heat recovery unit 6 through the exhaust port 5 and the three-way valve 38, and the other path enters the heat recovery unit 6 after passing through the exhaust port 4 and the exhaust turbine system. The air enters the intercooler 2 after being turbocharged by the exhaust gas, and then enters the cylinder to improve the intake efficiency.

[0026] Figure 2 It is a schematic diagram of the structure of an ammonia-hydrogen fuel engine 3, including an ammonia storage tank 11, an ammonia supply pump 12, a heat exchanger 13, a sensor 14, an ammonia fuel common rail 15, an ammonia return pipeline 16, an ammonia fuel injector 17, an engine body 18, a cylinder 19, an ammonia return control valve group 31, a gas-liquid separator 23, an electromagnetic three-way valve 22, a buffer tank 24, a self-boosting pump 25, and a mixer 30. The heat exchanger 13 is arranged in the ammonia supply unit to realize the overheating control of the ammonia fuel. The heat source comes from the exhaust gas of the ammonia-hydrogen fuel engine system. The ammonia fuel is sprayed into the cylinder 19 for combustion after overheating control, which can accelerate the combustion speed of the ammonia fuel and improve the combustion efficiency of the ammonia fuel. At the same time, a sensor 14 is arranged in the ammonia inlet pipeline to monitor the supplied fuel in real time. For the ammonia return control of the ammonia fuel, the ammonia fuel returns to the ammonia storage tank through the gas-liquid separator 23 and the self-boosting pump 25. The hydrogen fuel supply system includes a hydrogen storage tank 26, a pressure reducing valve 27, a buffer tank 28, an electromagnetic three-way valve 29, a hydrogen rail 20, and an active pre-combustion chamber 21. In addition, according to the engine operating conditions or external work requirements, ammonia can be controlled to enter the cylinder through the ammonia return control valve group 31 and the bypass line to mix with the cylinder air and hydrogen to perform fuel compensation.

[0027] Figure 3 This is a schematic diagram of the structure of the ammonia return control valve group, which is the core component of the ammonia return control unit. 31-1, 31-2, and 31-3 are electronic expansion valves with controllable openings. When 31-1 is opened and 31-2 and 31-3 are closed, the return ammonia is collected into the ammonia storage tank 11 through the self-boosting pump; when 31-1 and 31-2 are opened at the same time or 31-2 is opened alone and 31-3 is closed, the amount of ammonia entering the mixer 30 can be controlled by adjusting the opening of 31-2. 31-3 can be used as a safety valve, or in conjunction with the electromagnetic three-way valve 22, when 31-2 fails, the regulating function of the valve group can still be realized through valve 31-1 and the electromagnetic three-way valve 22.

[0028] Figure 4It is a schematic diagram of the structure of the heat recovery unit 6, including electromagnetic three-way valves 38, 37, No. 2 heat exchanger 32, No. 3 heat exchanger 39, turbines 33, 34, thermal cracker 40, expansion valve 35, and SCR post-processing device 36. The waste heat discharged from the exhaust gas turbocharger 1 enters the SCR device 36 for discharge after heat exchange in the No. 2 heat exchanger 32. The ammonia entering the thermal management system from the ammonia tank absorbs heat at the heat exchanger 32 and changes from liquid to ammonia steam, and enters the turbine 34 to expand and convert into mechanical energy output. The energy grade of ammonia coming out of the steam turbine 33 is lower than the energy grade of the primary exhaust gas entering from the tail gas port 5. Therefore, the ammonia entering the heat recovery unit 6 absorbs the exhaust gas in the heat exchanger 39 and becomes gaseous ammonia. After the ammonia is superheated, it can enter the thermal cracker 40 through the three-way valve 37 to decompose the ammonia into nitrogen and hydrogen, and the hydrogen enters the hydrogen storage tank as a pilot fuel. On the other hand, it can enter the SCR post-processing device 36 through the three-way valve. The waste gas generated from the cracked gas is converted into shaft power by the turbine 34 coaxial with the turbine 33 and then discharged. The waste heat discharged from the tail gas port 5 passes through the heat exchanger 39 and the expansion valve 35 and enters the SCR post-treatment device 36.

[0029] Figure 5 It is a schematic diagram of the structure of the cooling system 8, which includes a cooling water unit and a lubricating oil cooling unit. The cooling water unit includes a water tank 41, a radiator 42, an intercooler cooling water outlet 43, an engine cooling water outlet 47, a cooling water pump 48, an engine cooling water inlet 49, and an intercooler cooling water inlet 50; the lubricating oil cooling unit includes a lubricating oil tank 46, a radiator 44, and a lubricating oil pump 45.

[0030] The turbocharger is connected between the exhaust gas output end of the engine and the exhaust gas input end of the heat recovery unit, and the air output end of the turbocharger is connected to the air intake passage of the engine through a pipeline.

[0031] The fuel supply of the ammonia-hydrogen fuel engine includes a liquid ammonia supply unit, a hydrogen fuel supply unit, an ammonia return control unit, and an in-cylinder direct injection device.

[0032] The ammonia storage tank of the liquid ammonia supply unit is connected to the ammonia supply pump, and is connected to the ammonia fuel common rail pipe through the superheat heat exchanger and the sensor. An electrically controlled three-way valve with adjustable opening is arranged between the exhaust gas discharge pipeline and the No. 1 heat exchanger and the No. 3 heat exchanger to adjust the superheat degree of the liquid ammonia fuel and the ammonia gas, so as to realize the superheat control of the liquid ammonia fuel;

[0033] The ammonia storage tank is connected to the ammonia supply pump, a sensor is arranged in the ammonia inlet pipeline, the reversing valve in the ammonia return pipeline is connected to the gas-liquid separator on one side and to the hydrogen intake passage through the heat exchanger on the other side, the gas-liquid separator is connected to the buffer tank, the self-boosting pump and the ammonia storage tank in sequence; an ammonia return control valve group is arranged between the liquid ammonia cylinder direct injection device and the ammonia return storage tank and the mixer in the intake passage to adjust the amount of fuel supplied in the intake passage and control the ammonia return, and can also be connected to the mixer in the intake passage for fuel mixing and supply;

[0034] The hydrogen fuel supply unit controls the supply of hydrogen fuel. The hydrogen storage tank 26 is connected to the pressure reducing valve 22, connected to the hydrogen gas rail 20 through the buffer tank 28, and connected to the active pre-combustion chamber 21 for hydrogen ignition; the hydrogen fuel or hydrogen mixture is ignited by the spark plug in the pre-combustion chamber, enters the main combustion chamber through the pre-combustion chamber nozzle, and ignites the ammonia fuel.

[0035] The engine cooling unit is divided into a cooling water circuit and a lubricating oil cooling circuit, including a generator cooling water pump 48, radiators 42, 44, an intercooler, a lubricating oil pump 45, a lubricating oil tank 46, and a cooling water tank 41; in the cooling water circuit, the cooling water tank 41 is directly connected to the intercooler 2 and the engine 3, and the engine 3 and the intercooler are connected to the water pump and connected to the radiator 42; in the lubricating oil cooling circuit, the lubricating oil tank 46 is connected to the engine, and the engine is connected to the lubricating oil pump 45 and connected to the radiator 44.

[0036] The post-processor and the cracker form a multi-element coupling with the engine heat recovery unit. The heat recovery unit includes a multi-stage heat recovery component, a thermal cracker 40, an SCR post-processing device 36, and multiple heat exchangers. The exhaust pipe is divided into two parts, one of which is connected to the turbocharger and to the No. 2 heat exchanger, and finally connected to the SCR post-processor 36. The thermal design involved in this path is: the ammonia storage tank is connected to the No. 2 ammonia supply pump, the ammonia supply pump is connected to the heat exchanger, and connected to the multi-stage heat recovery component, the expansion end is connected to the No. 3 heat exchanger, and is respectively connected to the SCR reductant supply end and the thermal cracker 40 through a three-way valve; the other exhaust pipe does not pass through the turbocharger, but is directly connected to the three-way valve, and is respectively connected to the No. 1 heat exchanger for liquid ammonia fuel overheating control and the No. 3 heat exchanger for reheating the ammonia expanded by the multi-stage heat recovery component, and is connected downward to the expansion valve, and finally connected to the SCR post-processing device 36.

[0037] Figure 6 This is an ammonia-hydrogen fuel engine operation control method based on a liquid ammonia thermal management supply system. For the example proposed in the present invention, the operation process and control method of the entire engine are as follows:

[0038] When the engine is started, the hydrogen fuel enters the hydrogen pipeline after passing through the pressure reducing valve 27 in the hydrogen storage tank, and is stabilized in the buffer tank 28 to maintain a stable hydrogen supply. Due to the cold start of the engine and the difficulty in igniting the ammonia fuel, the hydrogen fuel enters the mixer 30 through the electromagnetic three-way valve 29, and enters the engine combustion chamber through the intake duct to play a role in combustion. The ammonia fuel is stored in the ammonia storage tank 11 in a high-pressure liquid state and is transported to the ammonia supply pipeline by the ammonia supply pump 12. The exhaust gas introduced from the engine exhaust port 5 can be regulated in the No. 1 heat exchanger 13 before the ammonia fuel enters the cylinder. The superheat is monitored by the sensor 14. After the hydrogen enters the pre-combustion chamber 21, it is ignited by the spark plug, and then enters the cylinder to ignite the high-ignition-point ammonia spray, and the engine is started and ignited.

[0039] When the engine is running stably, the hydrogen in the hydrogen storage tank 26 comes from the ammonia cracking reaction, so the hydrogen storage tank 26 itself only stores a small amount of hydrogen for starting to ensure the safety of the engine. The energy for online hydrogen production of ammonia comes from the waste heat recovery after the engine is running stably. A large amount of waste heat is fully utilized through the heat recovery unit 6. One of the engine exhaust waste heat mainly serves the overheating control of the liquid ammonia supply unit and the energy demand of the reducing agent ammonia in the ammonia cracker 40 and the SCR treatment device 36 to meet the temperature requirements of ammonia cracking or reduction. At the same time, through the action on ammonia, the engine shaft work compensation is realized. The ammonia coming out of the No. 2 heat exchanger 32 can convert heat into mechanical energy through the turbine 33. The high-temperature exhaust gas discharged from the engine exhaust port 5 is preheated by the three-way valve 38 to the ammonia fuel entering the cylinder according to the working conditions. The working fluid coming out of the turbine 33 is in a gas-liquid coexistence state with a higher temperature than liquid ammonia. The primary waste heat of the heat exchanger 39 is used to raise the ammonia to a higher temperature before entering the ammonia cracker 40. The exhaust gas after heat exchange from the heat exchanger 39 enters the SCR post-treatment system 36 through the expansion valve 35, completing the two-way exhaust gas recovery. The ammonia cracker 40 cracks ammonia into nitrogen and hydrogen, and the hydrogen enters the hydrogen storage tank 26 for storage. The nitrogen and cracked exhaust gas enter the post-treatment device after the thermal energy is converted into mechanical energy by the turbine 34. The other route mainly serves the exhaust turbine to pressurize the air. The high-temperature exhaust gas discharged from the engine exhaust port 4 pressurizes the air through the exhaust turbine 1 to increase the cylinder intake, and then enters the cylinder through the intercooler 2 and the heat exchanger 30.

[0040] When the engine is running, the low-pressure return ammonia fuel enters the ammonia storage tank 11 through self-boosting after passing through the valve group 31. At the same time, it can also enter the mixer 30 through the return ammonia control valve group 31, enter the engine through the intake duct, and cooperate with the hydrogen fuel supply unit to enter the mixer 30 through the electromagnetic three-way valve 29 to form a fuel self-compensation mechanism. The full range of operating conditions can be adapted by ammonia hydrogen fuel variable ratio compensation. When the engine load is large, a large concentration of ammonia fuel compensation can be performed through this mechanism to improve the power performance of the engine. When the load is small or when starting, a large concentration of hydrogen fuel compensation can be performed. When the engine is running stably, the combustion compensation pipeline can be closed, and the low-pressure return ammonia enters the gas-liquid separator 23 through the three-way valve 22. The ammonia is stored and stabilized before entering the buffer tank 24 before entering the self-boosting pump 25, and then pressurized to convert into liquid ammonia and return to the ammonia storage tank 11.

[0041] As can be seen from the above description, the present invention adopts the efficient coupling of the ammonia hydrogen engine body and the heat recovery unit, making full use of the waste heat energy of the engine, which not only improves the energy utilization efficiency but also completes the carbon-free emission of the system. The coupling of two injection modes, mainly direct injection in the cylinder and supplemented by intake port injection, is realized to strengthen the combustion in the engine cylinder, and realize the adjustable injection mode of multiple working conditions to adapt to the various injection requirements of the engine. The heat recovery unit is used to adjust the ammonia hydrogen fuel engine supply system to solve the inherent properties of ammonia fuel with high ignition point and slow combustion speed. Waste heat is utilized by exhaust gas turbocharging, preheating by waste heat recovery and ammonia energy supplement, and shaft power compensation is realized by the output shaft work of the turbine, which provides energy for thermal cracking of ammonia and exhaust gas post-treatment, and realizes engine integration and improves safety to a certain extent. The synergistic effect of the ammonia hydrogen engine system and the heat recovery unit greatly improves the thermal efficiency of the engine, and realizes zero carbon emissions of the entire power system.

Claims

1. An ammonia-hydrogen fuel engine based on a liquid ammonia thermal management supply system, characterized by: The invention comprises an ammonia hydrogen fuel engine, a heat recovery unit, a cooling unit and a turbocharger. The turbocharger is connected between the ammonia hydrogen fuel engine and the heat recovery unit. The ammonia hydrogen fuel engine comprises an ammonia storage tank, a hydrogen storage tank, an ammonia fuel common rail pipe, an engine body, an ammonia return control valve group and a mixer. The ammonia storage tank is connected to the ammonia fuel common rail pipe, the hydrogen storage tank is connected to the hydrogen gas rail through a hydrogen buffer tank, cylinders, ammonia fuel injectors and active pre-combustion chambers are respectively arranged in the engine body, the ammonia fuel injectors and the active pre-combustion chambers are respectively connected to the cylinders, the ammonia fuel common rail pipe is connected to the ammonia fuel injectors, the hydrogen gas rail is connected to the active pre-combustion chamber, the ammonia return control valve group comprises a first, a second and a third electronic expansion valve with controllable opening, the first electronic expansion valve is connected to the third electronic expansion valve in parallel, and both are connected to the second electronic expansion valve, the first electronic expansion valve and the third electronic expansion valve are respectively connected to the first electromagnetic three-way valve, the first electromagnetic three-way valve is connected to the ammonia storage tank through the ammonia buffer tank, the first electronic expansion valve is also connected to the ammonia fuel injector, the third electronic expansion valve is also connected to the mixer, and the mixer is respectively connected to the pipeline between the turbocharger and the hydrogen buffer tank and the hydrogen gas rail; when the first electronic expansion valve is opened and the second and third electronic expansion valves are closed, the return ammonia is collected into the ammonia storage tank through the return ammonia control valve group, when the first electronic expansion valve and the second electronic expansion valve are opened at the same time or the second electronic expansion valve is opened alone and the third electronic expansion valve is closed, the amount of ammonia entering the mixer is controlled by adjusting the opening of the second electronic expansion valve, and the third electronic expansion valve cooperates with the first electromagnetic three-way valve, and when the second electronic expansion valve fails, the adjustment function of the valve group can still be realized through the first electronic expansion valve and the first electromagnetic three-way valve; The heat recovery unit includes an SCR post-processing device, a turbine, a steam turbine, and a thermal cracker. The waste heat discharged from the exhaust gas turbocharger is discharged into the SCR post-processing device after heat exchange by the second heat exchanger. Part of the ammonia from the ammonia storage tank is converted from liquid to ammonia vapor after absorbing the waste heat by the second heat exchanger, and then enters the steam turbine for expansion and conversion into mechanical energy output; The ammonia entering the heat recovery unit absorbs the exhaust gas in the third heat exchanger for superheating and becomes gaseous ammonia, and then passes through a three-way valve. One path can enter the thermal cracker to decompose the ammonia into nitrogen and hydrogen. The hydrogen enters the hydrogen storage tank as a pilot fuel, and the exhaust gas generated by the cracking is converted into shaft power by a turbine coaxial with the steam turbine and then discharged; the other path after passing through the three-way valve enters the SCR post-processing device through a three-way valve, and the waste heat discharged from the engine exhaust port passes through the third heat exchanger and the expansion valve into the SCR post-processing device.

2. The ammonia-hydrogen fuel engine based on the liquid ammonia thermal management supply system according to claim 1 is characterized in that: The cooling unit includes a first radiator, a second radiator, a lubricating oil tank, a water tank, a cooling water pump, and a lubricating oil pump. The two ends of the first radiator are respectively connected to the water tank and the cooling water pump, the water tank is connected to the engine cooling water inlet, and the cooling water pump is connected to the engine cooling water outlet. The two ends of the second radiator are respectively connected to the lubricating oil tank and the lubricating oil pump, and the lubricating oil tank and the lubricating oil pump are both connected to the ammonia hydrogen fuel engine.

3. An operation control method of an ammonia-hydrogen fuel engine based on the liquid ammonia thermal management supply system according to claim 1 or 2, characterized in that: When the engine is started, the liquid ammonia supply unit supplies liquid ammonia fuel to the ammonia fuel common rail and the ammonia fuel in-cylinder direct injection device. The hydrogen fuel is used as the ignition and combustion-supporting fuel of the ammonia fuel. At this time, the ammonia fuel cracker is not running. The hydrogen fuel is operated through the hydrogen stored in the hydrogen storage tank. Part of the hydrogen fuel is supplied to the in-cylinder injection device. After ignition, the jet ignites the ammonia fuel injected into the cylinder, and the other part enters the combustion chamber through the intake duct for combustion support.

4. The operation control method of an ammonia-hydrogen fuel engine based on a liquid ammonia thermal management supply system according to claim 3 is characterized in that: When the engine is running, the liquid ammonia supplied by the liquid ammonia supply component enters the cylinder injection device after completing overheat control, and the other part of the ammonia fuel is gasified into ammonia and enters the multi-stage heat recovery component, the ammonia cracker and the SCR post-treatment device. The exhaust heat energy of the internal combustion engine provides energy for the ammonia cracking reaction in the ammonia cracker and the SCR post-treatment device. During operation, the ammonia cracker works, and the hydrogen produced after the ammonia cracking reaction meets the needs of the internal combustion engine. At the same time, the additional exhaust gas is compensated for shaft work through the turbine. If the hydrogen fuel meets the use requirements at this time, the liquid ammonia supply component stops supplying, and the fuel cylinder injection device injects the hydrogen, ammonia and nitrogen mixture produced after the ammonia cracking reaction from the hydrogen storage tank into the cylinder of the ammonia-hydrogen internal combustion engine, and at the same time enters the combustion chamber through the mixer of the intake duct as ammonia combustion-supporting fuel.

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