Liquid ammonia-hydrogen-electricity hybrid power engine system and working method thereof

Abstract

A liquid ammonia-hydrogen-electricity hybrid power engine system comprises a double direct injection ammonia engine, a power battery, a liquid ammonia evaporator and an ammonia part catalytic cracking device. The double direct injection ammonia engines and the power battery provide power output at the same time or alternatively; the double-direct-injection ammonia engine is provided with two fuel direct-injection inlets, an air inlet and a waste gas outlet, and the two fuel direct-injection inlets are connected with liquid ammonia and ammonia-hydrogen-nitrogen mixed gas respectively; the liquid ammonia evaporator gasifies part of liquid ammonia, and obtained ammonia gas is input into the ammonia part catalytic cracking device and cracked in the ammonia part catalytic cracking device to obtain ammonia-hydrogen-nitrogen mixed gas; a part of output of the double direct injection ammonia engine is converted into electric energy to be stored in the power battery, the power battery provides the electric energy for the electric auxiliary heating cold starting device, and the electric auxiliary heating cold starting device is used for achieving cold starting of the liquid ammonia evaporator and the ammonia part catalytic cracking device. According to the invention, the emission of pollutants can be controlled at a lower level, and the problem that the combustion characteristic is poor when liquid ammonia is used as fuel for ignition is solved at the same time.

Description

Technical Field

[0001] The present invention relates to an ammonia hybrid power engine system, and in particular to a liquid ammonia-hydrogen-electric hybrid power engine system and a working method thereof. Background Art

[0002] The use of carbon-free fuels such as hydrogen and ammonia in the automotive field can reduce carbon dioxide emissions. Hydrogen can be stored and transported in the form of high-pressure gas cylinders, but it is expensive and has a short driving range.

[0003] Ammonia can be synthesized from hydrogen as raw material, and the storage and transportation pressure and temperature parameters are low, and the cost is low. When the engine uses ammonia fuel, in order to increase the engine power, liquid ammonia direct injection is often used to achieve high-power combustion. However, due to the low laminar flame speed and high minimum ignition energy of liquid ammonia combustion, its combustion stability is poor. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a liquid ammonia-hydrogen-electric hybrid engine system and its working method, select the technical route of liquid ammonia vaporization, online partial cracking to produce hydrogen and using ammonia hydrogen nitrogen mixed gas to improve combustion, firstly solve the stability problem of liquid ammonia injection combustion, secondly solve the engine cold start problem by coupling power battery and electric auxiliary heat cold start device, and thirdly improve the system efficiency by using waste heat of exhaust gas and cooling water. In addition, the present invention can also select the operation mode and control the flow rate and cracking volume ratio of ammonia cracking through the central control unit, intelligently control the stable combustion, nitrogen oxides and unburned ammonia hydrogen emissions, achieve zero carbon emissions, and achieve the optimal operation state at the same time.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A liquid ammonia-hydrogen-electric hybrid engine system, comprising a dual direct injection ammonia engine, a power battery, a liquid ammonia evaporator and an ammonia partial catalytic cracking device; the dual direct injection ammonia engine and the power battery provide power output simultaneously or selectively;

[0007] The dual direct injection ammonia engine has two fuel direct injection inlets, one air inlet and one exhaust gas outlet, and the two fuel direct injection inlets are respectively connected to liquid ammonia and ammonia hydrogen nitrogen mixed gas;

[0008] The liquid ammonia evaporator vaporizes part of the liquid ammonia, and the obtained ammonia gas is fed into the ammonia partial catalytic cracking device and cracked therein to obtain the ammonia hydrogen nitrogen mixed gas;

[0009] A portion of the output of the dual direct injection ammonia engine is converted into electrical energy and stored in a power battery, which provides electrical energy for an electric auxiliary heat cold start device, which is used to achieve a cold start of the liquid ammonia evaporator and the ammonia partial catalytic cracking device.

[0010] In one embodiment, the dual direct injection ammonia engine has two fuel supply modes, namely, a liquid ammonia direct injection mode for increasing power and an ammonia-hydrogen-nitrogen mixed gas direct injection mode, in which hydrogen is used as a combustion aid to improve combustion.

[0011] In one embodiment, the liquid ammonia-hydrogen-electric hybrid engine system further includes: a liquid ammonia tank, a liquid ammonia pump, and an ammonia-hydrogen gas compressor;

[0012] The two direct fuel injection inlets are respectively connected to the liquid ammonia pump and the ammonia-hydrogen gas compressor; the liquid ammonia pump is connected to one outlet of the liquid ammonia tank, and the other outlet of the liquid ammonia tank is connected to the liquid ammonia inlet of the liquid ammonia evaporator; the ammonia-hydrogen gas compressor is connected to the mixed gas outlet of the ammonia partial catalytic cracking device.

[0013] In one embodiment, the liquid ammonia-hydrogen-electric hybrid engine system further includes: an exhaust gas heat exchanger;

[0014] The exhaust gas outlet of the dual direct injection ammonia engine is connected to the heat source inlet of the exhaust gas heat exchanger, and the heat source outlet of the exhaust gas heat exchanger is connected to the selective catalytic reduction device and the catalytic oxidation device in sequence; the exhaust gas heat absorbed by the exhaust gas heat exchanger is transferred to the liquid ammonia evaporator and the ammonia partial catalytic cracking device respectively, providing heat for the gasification and cracking of liquid ammonia.

[0015] In one embodiment, the liquid ammonia-hydrogen-electric hybrid engine system further includes: a cooling water heat exchanger;

[0016] The heat source inlet of the cooling water heat exchanger is connected to the cooling water outlet of the cooling water jacket of the dual direct injection ammonia engine. The waste heat of the cooling water absorbed by the cooling water heat exchanger is transferred to the liquid ammonia evaporator and the ammonia partial catalytic cracking device respectively to provide heat for the gasification and cracking of liquid ammonia.

[0017] In one embodiment, the liquid ammonia-hydrogen-electric hybrid engine system further includes: a central control unit;

[0018] The central control unit centrally controls various fuel supply components, valves, sensors, various heat transfers, and detects the composition and content of emissions in the tail gas.

[0019] In one embodiment, the fuel and air supply of the dual direct injection ammonia engine is controlled, wherein the equivalence ratio is controlled to be 1.15, liquid ammonia is directly injected into the cylinder, and gaseous ammonia is controlled to have a cracking volume ratio of 0-30% through an ammonia partial catalytic cracking device.

[0020] The working method of the liquid ammonia-hydrogen-electric hybrid engine system of the present invention comprises:

[0021] When the dual direct injection ammonia engine is started, the power battery provides electric energy to the electric auxiliary heat cold start device, supplies heat to the liquid ammonia evaporator and the ammonia partial catalytic cracking device, supplies liquid ammonia to the liquid ammonia evaporator to evaporate and vaporize, and passes into the ammonia partial catalytic cracking device to partially crack into ammonia hydrogen nitrogen mixed gas, and the ammonia hydrogen nitrogen mixed gas is directly injected into the dual direct injection ammonia engine for ignition. After ignition, liquid ammonia is directly injected into the dual direct injection ammonia engine for combustion. During stable operation, the power proportion of the ammonia hydrogen nitrogen mixed gas injection is controlled within 10%;

[0022] When unstable combustion of liquid ammonia occurs, the liquid ammonia evaporator and the ammonia partial catalytic cracking device are controlled according to the unstable combustion signal received to increase the ammonia flow rate of evaporation, vaporization and cracking and the ammonia cracking volume ratio, thereby increasing the hydrogen ratio in the ammonia-hydrogen-nitrogen mixed gas and improving the combustion stability; at this time, the power proportion of the ammonia-hydrogen-nitrogen mixed gas injection is controlled within 20%, of which the hydrogen volume ratio is controlled within 50%;

[0023] When outputting power, the dual direct injection ammonia engine and the power battery provide power output simultaneously or selectively, and the dual direct injection ammonia engine generates electricity to provide electrical energy to the power battery.

[0024] In one embodiment, after the engine is started, the heat in the combustion exhaust gas is recovered by the exhaust gas heat exchanger and transferred to the liquid ammonia evaporator and the ammonia partial catalytic cracking device respectively;

[0025] The cooling water heat exchanger is used to recover the heat in the cooling water of the dual direct injection ammonia engine and transfer it to the liquid ammonia evaporator and the ammonia partial catalytic cracking unit respectively.

[0026] In one embodiment, the ammonia power range of the dual direct injection ammonia engine is 100-300 kW, and the thermal efficiency of the entire system is close to 60%.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] Compared with the prior art, the liquid ammonia-hydrogen-electric hybrid engine system of the present invention improves combustion stability by gasifying liquid ammonia and partially cracking ammonia through an ammonia catalytic cracking device to form an ammonia-hydrogen mixed gas. By coupling the power battery, an electric auxiliary heat cold start device is used to solve the cold start problem of the liquid ammonia evaporator and the ammonia partial catalytic cracking device. The system efficiency is improved by utilizing the waste heat of exhaust gas and cooling water. The present invention can also select the operating mode and control the flow rate and cracking volume ratio of ammonia cracking through a central control unit, intelligently control stable combustion, nitrogen oxides and unburned ammonia hydrogen emissions, achieve zero carbon emissions, and achieve the optimal operating state. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the system structure of the present invention. DETAILED DESCRIPTION

[0030] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0031] Traditional ammonia fuel engines have poor combustion stability and low overall system efficiency. To this end, the present invention provides a liquid ammonia-hydrogen-electric hybrid engine system, which uses an "ammonia-hydrogen co-combustion" concept to regulate the ammonia flame with hydrogen. On the one hand, the high activity of hydrogen promotes the stability of ammonia combustion. On the other hand, hydrogen is obtained by cracking ammonia downstream, and combustion does not require strict requirements on the purity of hydrogen, ultimately achieving decarbonization of the fuel system.

[0032] like Figure 1 As shown, the present invention is a liquid ammonia-hydrogen-electric hybrid engine system, which mainly includes a dual direct injection ammonia engine 3, a power battery 4, a liquid ammonia evaporator 10 and an ammonia partial catalytic cracking device 11. The power of the dual direct injection ammonia engine 3 and the power battery 4 are in a parallel relationship, and can provide power output 5 simultaneously or selectively.

[0033] The dual direct injection ammonia engine 3 of the present invention has two fuel direct injection inlets, namely a liquid fuel direct injection inlet and a gaseous fuel direct injection inlet, which are connected to liquid ammonia and ammonia hydrogen nitrogen mixed gas respectively. Accordingly, there are two fuel supply modes, namely a liquid ammonia direct injection mode and an ammonia hydrogen nitrogen mixed gas direct injection mode. The liquid ammonia direct injection mode can increase power, and the hydrogen injected in the ammonia hydrogen nitrogen mixed gas direct injection mode can be used as a combustion aid to improve combustion. At the same time, the dual direct injection ammonia engine 3 also has an air inlet for injecting air, and an exhaust gas outlet for discharging exhaust gas.

[0034] The liquid ammonia evaporator 10 is a device that uses heat energy to evaporate and gasify liquid ammonia. The ammonia gas obtained is sent to the ammonia partial catalytic cracking device 11, and the ammonia gas is cracked in the ammonia partial catalytic cracking device 11 to obtain an ammonia hydrogen nitrogen mixed gas.

[0035] That is, the present invention directly injects a portion of liquid ammonia into the dual direct injection ammonia engine 3, and takes another portion of liquid ammonia for evaporation and gasification, catalytic cracking to obtain ammonia hydrogen nitrogen mixed gas, and the ammonia hydrogen nitrogen mixed gas is also injected into the dual direct injection ammonia engine 3, and the ammonia hydrogen nitrogen mixed gas is used for ignition and combustion stability is improved. The present invention can control pollutant emissions at a relatively low level, and at the same time solves the problem of poor combustion characteristics when liquid ammonia is used as fuel for ignition.

[0036] The power battery 4 of the present invention can be charged by external power, or a part of the energy output by the dual direct injection ammonia engine 3 can be converted into electric energy and stored in the power battery 4. In addition to providing power output 5, the power battery 4 can also provide electric energy for the electric auxiliary heat cold starting device 13, and the cold starting of the liquid ammonia evaporator 10 and the ammonia partial catalytic cracking device 11 can be achieved through the electric auxiliary heat cold starting device 13.

[0037] Through combination, the system of the present invention has multiple power output forms, namely, direct output of the dual direct injection ammonia engine 3, direct output of the power battery 4, and coupled output of the dual direct injection ammonia engine 3 and the power battery 4. The power of the power battery 4 can come from the power generation and charging input of the dual direct injection ammonia engine 3.

[0038] In the embodiments of the present invention, continue to refer to Figure 1 The liquid ammonia-hydrogen-electric hybrid engine system may also include: a liquid ammonia tank 1, a liquid ammonia pump 2 and an ammonia-hydrogen gas compressor 12.

[0039] The liquid ammonia tank 1 is used to store and provide the liquid ammonia required by the system. It has two outlets. One outlet is connected to the liquid fuel direct injection inlet of the dual direct injection ammonia engine 3 through the liquid ammonia pump 2, and the liquid ammonia is injected into the dual direct injection ammonia engine 3 under pressure through the liquid ammonia pump 2. The other outlet is connected to the liquid ammonia evaporator 10 to provide liquid ammonia for evaporation. The ammonia hydrogen gas compressor 12 is connected to the mixed gas output pipeline of the ammonia partial catalytic cracking device 11, and the obtained ammonia hydrogen nitrogen mixed gas is injected into the dual direct injection ammonia engine 3 under pressure.

[0040] That is, the dual direct injection ammonia engine 3 of the present invention has two fuel sources, one is that the liquid ammonia pump 2 directly pressurizes the liquid ammonia in the liquid ammonia tank 1 and directly injects it. The other is that the liquid ammonia is vaporized by the liquid ammonia evaporator 10, partially cracked into ammonia hydrogen nitrogen mixed gas by the ammonia partial catalytic cracking device 11, and then directly injected after passing through the ammonia hydrogen gas compressor 12.

[0041] In the embodiments of the present invention, continue to refer to Figure 1 The liquid ammonia-hydrogen-electric hybrid engine system may further include: an exhaust gas heat exchanger 6. The exhaust gas heat exchanger 6 is used to recover the exhaust gas waste heat of the dual direct injection ammonia engine 3 and provide it to the liquid ammonia evaporation and catalytic cracking process.

[0042] Specifically, the heat source inlet of the exhaust gas heat exchanger 6 is connected to the exhaust gas outlet of the dual direct injection ammonia engine 3, and the heat source outlet of the exhaust gas heat exchanger 6 is connected to the selective catalytic reduction device 7 and the catalytic oxidation device 8 in sequence, and the exhaust gas after heat exchange is discharged to the selective catalytic reduction device 7, and then flows to the catalytic oxidation device 8. The functions of the selective catalytic reduction device 7 and the catalytic oxidation device 8 are to treat the exhaust gas after heat exchange so that the tail gas finally discharged from the system meets the environmental protection requirements. Specifically, the selective catalytic reduction device 7 converts the nitrogen oxides contained in the exhaust gas into nitrogen, and the conversion efficiency reaches 100%. The catalytic oxidation device 8 oxidizes the unburned ammonia and hydrogen in the exhaust gas into nitrogen and water, and the conversion efficiency reaches 100%. The main components of the final emission are nitrogen and water vapor, and zero carbon and pollution-free emission are achieved. The exhaust gas heat exchanger 6 has two cold source outlets, which are respectively connected to the liquid ammonia evaporator 10 and the ammonia partial catalytic cracking device 11, so that the exhaust heat absorbed by the cold source is transferred to these two devices to provide heat for the gasification and cracking of liquid ammonia.

[0043] In the embodiments of the present invention, continue to refer to Figure 1 The liquid ammonia-hydrogen-electric hybrid engine system may further include: a cooling water heat exchanger 9. The cooling water heat exchanger 9 is used to recover the cooling water heat of the dual direct injection ammonia engine 3 and provide it to the liquid ammonia evaporation and catalytic cracking process.

[0044] Specifically, the heat source inlet of the cooling water heat exchanger 9 is connected to the cooling water outlet of the cooling water jacket of the dual direct injection ammonia engine 3, and the cold source outlet of the cooling water heat exchanger 9 is respectively connected to the liquid ammonia evaporator 10 and the ammonia partial catalytic cracking device 11, so that the cooling water heat absorbed by the cold source is transferred to these two devices to provide heat for the gasification and cracking of liquid ammonia.

[0045] Therefore, there are three sources of heat for the liquid ammonia evaporator 10 and the ammonia partial catalytic cracking device 11 of the present invention. During cold start, the heat comes from the electric auxiliary heat cold start device 13 driven by the power battery 4. When the dual direct injection ammonia engine 3 is working, the waste heat of the exhaust gas is supplied to the liquid ammonia evaporator 10 and the ammonia partial catalytic cracking device 11 respectively through the exhaust gas heat exchanger 6. The waste heat in the cooling water of the dual direct injection ammonia engine 3 is supplied to the liquid ammonia evaporator 10 and the ammonia partial catalytic cracking device 11 respectively through the cooling water heat exchanger 9. By utilizing the above waste heat, the thermal efficiency of the system is improved.

[0046] In the embodiments of the present invention, continue to refer to Figure 1The liquid ammonia-hydrogen-electric hybrid engine system may also include: a central control unit 14. The central control unit 14 is a master control part that can uniformly control various fuel supply components, valves, sensors, various heat transfers, and detect the composition and content of exhaust emissions. In this embodiment, automatic control is added, that is, the central control unit 14. The central control unit 14 detects the composition and content of the exhaust gas, and then adjusts the supply amount of each fuel to make the thermal efficiency of the dual direct injection ammonia engine 3 at a better performance and the emissions at a lower level.

[0047] For example, the fuel and air supply of the dual direct injection ammonia engine 3 can be controlled by the central control unit 14, wherein the equivalence ratio is controlled to be about 1.15, liquid ammonia is directly injected into the cylinder, and the gaseous ammonia is controlled to have a cracking volume ratio of 0-30% through the ammonia partial catalytic cracking device 11. Under this condition, the system can achieve a better operation. The ammonia power range of the dual direct injection ammonia engine 3 is 100-300kW, and the thermal efficiency of the entire system is close to 60%.

[0048] The working method of the liquid ammonia-hydrogen-electric hybrid engine system of the present invention comprises:

[0049] When the dual direct injection ammonia engine 3 is started, the power battery 4 provides electric energy to the electric auxiliary heat cold start device 13, supplies heat to the liquid ammonia evaporator 10 and the ammonia partial catalytic cracking device 11, and the liquid ammonia tank 1 supplies liquid ammonia to the liquid ammonia evaporator 10 to evaporate and vaporize it under heat, and passes it into the ammonia partial catalytic cracking device 11 to partially crack it into an ammonia hydrogen nitrogen mixture. The ammonia hydrogen nitrogen mixture is directly injected into the dual direct injection ammonia engine 3 through the ammonia hydrogen gas compressor 12, and the ignition energy and stability are reduced by hydrogen. After ignition, the liquid ammonia is pressurized and directly injected from the liquid ammonia tank 1 through the liquid ammonia pump 2 to the dual direct injection ammonia engine 3 for combustion. During stable operation, the power proportion of the ammonia hydrogen nitrogen mixture injection is controlled within 10%.

[0050] After the engine is started, in order to realize heat recycling, the combustion exhaust gas is passed into the exhaust gas heat exchanger 6, and the exhaust gas heat exchanger 6 is used to recover the heat in the combustion exhaust gas, and the heat is respectively transferred to the liquid ammonia evaporator 10 and the ammonia partial catalytic cracking device 11, so as to realize energy cascade utilization. The cooling water in the cooling water jacket of the dual direct injection ammonia engine 3 is passed into the cooling water heat exchanger 9, and the heat in the cooling water of the dual direct injection ammonia engine 3 is recovered by the cooling water heat exchanger 9, and the heat is respectively transferred to the liquid ammonia evaporator 10 and the ammonia partial catalytic cracking device 11, so as to realize energy cascade utilization. The exhaust gas heat exchanger 6 and the cooling water heat exchanger 9 can be used at the same time, or one of them can be used selectively.

[0051] When unstable combustion of liquid ammonia occurs, the liquid ammonia evaporator 10 and the ammonia partial catalytic cracking device 11 are controlled according to the unstable combustion signal received by the central control unit 14 to increase the ammonia flow rate and the ammonia cracking volume ratio of evaporation, vaporization and cracking, thereby increasing the hydrogen ratio in the ammonia-hydrogen-nitrogen mixed gas, improving the combustion stability, and achieving the purpose of improving the combustion stability. At this time, the power proportion of the ammonia-hydrogen-nitrogen mixed gas injection is controlled within 20%, wherein the hydrogen volume ratio is controlled within 50%.

[0052] When outputting power, in various strategies, the dual direct injection ammonia engine 3 and the power battery 4 can provide power output 5 simultaneously or selectively, wherein a part of the output of the dual direct injection ammonia engine 3 is used for work, and a part is converted into electrical energy and stored in the power battery 4. In low working conditions, the power battery 4 can provide heat for the liquid ammonia evaporator 10 and the ammonia partial catalytic cracking device 11 through the electric auxiliary heat cold start device 13 and the waste heat of the dual direct injection ammonia engine 3. The coupling control strategy of the waste heat of the dual direct injection ammonia engine 3 and the electric auxiliary heat is provided by the central control unit 14.

[0053] In summary, the system can improve combustion stability by gasifying liquid ammonia and partially cracking ammonia online through an ammonia catalytic cracking device to form an ammonia-hydrogen mixed gas. By coupling the power battery system, on the one hand, the cold start problem of the liquid ammonia evaporator and the ammonia partial catalytic cracking device is solved through the electric auxiliary heat cold start device. The waste heat utilization of exhaust gas and cooling water improves the system efficiency. The present invention can also select the operating mode and control the flow rate and cracking volume ratio of ammonia cracking through a central control unit, intelligently control stable combustion, nitrogen oxides and unburned ammonia hydrogen emissions, achieve zero carbon emissions, and achieve a better operating state.

[0054] The above are only preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solution and invention concept of the present invention within the scope disclosed by the present invention, which are within the protection scope of the present invention.

Claims

1. A liquid ammonia-hydrogen-electric hybrid engine system, characterized in that: It comprises a dual direct injection ammonia engine (3), a power battery (4), a liquid ammonia evaporator (10) and an ammonia partial catalytic cracking device (11); the dual direct injection ammonia engine (3) and the power battery (4) provide power output (5) simultaneously or selectively; The dual direct injection ammonia engine (3) has two fuel direct injection inlets, an air inlet and an exhaust gas outlet, and the two fuel direct injection inlets are respectively connected to liquid ammonia and ammonia hydrogen nitrogen mixed gas; The liquid ammonia evaporator (10) vaporizes part of the liquid ammonia, and the obtained ammonia gas is input into the ammonia partial catalytic cracking device (11) and cracked therein to obtain the ammonia hydrogen nitrogen mixed gas; A portion of the output of the dual direct injection ammonia engine (3) is converted into electrical energy and stored in a power battery (4). The power battery (4) provides electrical energy for an electric auxiliary heat cold start device (13). The electric auxiliary heat cold start device (13) is used to achieve cold start of the liquid ammonia evaporator (10) and the ammonia partial catalytic cracking device (11).

2. The liquid ammonia-hydrogen-electric hybrid engine system according to claim 1, characterized in that: The dual direct injection ammonia engine (3) has two fuel supply modes, namely a liquid ammonia direct injection mode for increasing power and an ammonia hydrogen nitrogen mixed gas direct injection mode, in which hydrogen is used as a combustion aid to improve combustion.

3. The liquid ammonia-hydrogen-electric hybrid engine system according to claim 1, characterized in that: The liquid ammonia-hydrogen-electric hybrid engine system further comprises: a liquid ammonia tank (1), a liquid ammonia pump (2) and an ammonia-hydrogen gas compressor (12); The two fuel direct injection inlets are respectively connected to the liquid ammonia pump (2) and the ammonia hydrogen gas compressor (12); the liquid ammonia pump (2) is connected to one outlet of the liquid ammonia tank (1); the other outlet of the liquid ammonia tank (1) is connected to the liquid ammonia inlet of the liquid ammonia evaporator (10); the ammonia hydrogen gas compressor (12) is connected to the mixed gas outlet of the ammonia partial catalytic cracking device (11).

4. The liquid ammonia-hydrogen-electric hybrid engine system according to claim 2 or 3, characterized in that: The liquid ammonia-hydrogen-electric hybrid engine system further comprises: an exhaust gas heat exchanger (6); The exhaust gas outlet of the dual direct injection ammonia engine (3) is connected to the heat source inlet of the exhaust gas heat exchanger (6), and the heat source outlet of the exhaust gas heat exchanger (6) is connected to the selective catalytic reduction device (7) and the catalytic oxidation device (8) in sequence; the exhaust gas heat absorbed by the exhaust gas heat exchanger (6) is transferred to the liquid ammonia evaporator (10) and the ammonia partial catalytic cracking device (11) respectively, so as to provide heat for the gasification and cracking of the liquid ammonia.

5. The liquid ammonia-hydrogen-electric hybrid engine system according to claim 4, characterized in that: The liquid ammonia-hydrogen-electric hybrid engine system further comprises: a cooling water heat exchanger (9); The heat source inlet of the cooling water heat exchanger (9) is connected to the cooling water outlet of the cooling water jacket of the dual direct injection ammonia engine (3), and the waste heat of the cooling water absorbed by the cooling water heat exchanger (9) is respectively transferred to the liquid ammonia evaporator (10) and the ammonia partial catalytic cracking device (11), thereby providing heat for the vaporization and cracking of the liquid ammonia.

6. The liquid ammonia-hydrogen-electric hybrid engine system according to claim 5, characterized in that: The liquid ammonia-hydrogen-electric hybrid engine system further comprises: a central control unit (14); The central control unit (14) centrally controls various fuel supply components, valves, sensors, various heat transfers, and detects the composition and content of emissions in the tail gas.

7. The liquid ammonia-hydrogen-electric hybrid engine system according to claim 1, characterized in that: The fuel and air supply amounts of the dual direct injection ammonia engine (3) are controlled, wherein the equivalence ratio is controlled to be 1.15, liquid ammonia is directly injected into the cylinder, and gaseous ammonia is controlled to be cracked by the ammonia partial catalytic cracking device (11) at a volume ratio of 0-30%.

8. The operating method of the liquid ammonia-hydrogen-electric hybrid engine system according to any one of claims 1 to 7, characterized in that: When the dual direct injection ammonia engine (3) is started, the power battery (4) provides electric energy to the electric auxiliary heat cold start device (13), supplies heat to the liquid ammonia evaporator (10) and the ammonia partial catalytic cracking device (11), supplies liquid ammonia to the liquid ammonia evaporator (10) to evaporate and vaporize, and passes into the ammonia partial catalytic cracking device (11) to partially crack into ammonia hydrogen nitrogen mixed gas, and the ammonia hydrogen nitrogen mixed gas is directly injected into the dual direct injection ammonia engine (3) for ignition. After ignition, liquid ammonia is directly injected into the dual direct injection ammonia engine (3) for combustion, and during stable operation, the power proportion of the ammonia hydrogen nitrogen mixed gas injection is controlled within 10%; When unstable combustion of liquid ammonia occurs, the liquid ammonia evaporator (10) and the ammonia partial catalytic cracking device (11) are controlled according to the received unstable combustion signal to increase the flow rate of ammonia gas vaporized and cracked and the ammonia cracking volume ratio, thereby increasing the proportion of hydrogen in the ammonia-hydrogen-nitrogen mixed gas and improving the combustion stability; At this time, the power ratio of the ammonia-hydrogen-nitrogen mixed gas injection is controlled within 20%, among which the volume ratio of hydrogen is controlled within 50%; When outputting power, the dual direct injection ammonia engine (3) and the power battery (4) provide power output (5) simultaneously or selectively, and the dual direct injection ammonia engine (3) generates electricity to provide electric energy to the power battery (4).

9. The working method according to claim 8, characterized in that: After the engine is started, the heat in the combustion exhaust gas is recovered by using the exhaust gas heat exchanger (6) and transferred to the liquid ammonia evaporator (10) and the ammonia partial catalytic cracking device (11) respectively; A cooling water heat exchanger (9) is used to recover heat from cooling water of a dual direct injection ammonia engine (3), and the heat is transferred to a liquid ammonia evaporator (10) and an ammonia partial catalytic cracking device (11) respectively.

10. The working method according to claim 8, characterized in that: The ammonia power of the dual direct injection ammonia engine (3) is in the range of 100-300 kW, and the thermal efficiency of the entire system is close to 60%.

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