A control method for high-pressure direct injection of liquid ammonia and an ammonia fuel supply system

Abstract

The present disclosure provides a control method for high-pressure direct injection of liquid ammonia and an ammonia fuel supply system, the ammonia fuel supply system comprising a liquid ammonia storage module and a high-pressure injection module, the liquid ammonia storage module comprising a nitrogen source of a first air pressure, a liquid ammonia storage tank of a second air pressure, and a liquid ammonia buffer tank of a third air pressure; the control method comprises: using a liquid level gauge on the liquid ammonia buffer tank to measure the liquid level of the liquid ammonia in the liquid ammonia buffer tank in real time; when the liquid level does not meet a preset height range, controlling the working state of the solenoid valve to adjust the injection amount of nitrogen in the nitrogen source into the liquid ammonia storage tank, the injection amount of nitrogen can change the pressure difference between the liquid ammonia storage tank and the liquid ammonia buffer tank, so as to change the speed at which the liquid ammonia in the liquid ammonia storage tank is injected into the liquid ammonia buffer tank; when the liquid level meets the preset height range, pumping the liquid ammonia in the liquid ammonia buffer tank to the high-pressure injection module according to a preset supply amount; the high-pressure injection module injects the preset supply amount of liquid ammonia into the engine cylinder for combustion and work.

Description

Technical Field

[0001] The present disclosure relates to the field of internal combustion engines, and in particular to a control method for high-pressure direct injection of liquid ammonia and an ammonia fuel supply system. Background Art

[0002] Ammonia is a hydrogen-rich carrier fuel other than hydrogen. It contains no carbon and its complete combustion products are only nitrogen and water, making it a clean, renewable alternative fuel. Furthermore, ammonia offers significant advantages due to its low storage and transportation costs and mature production process.

[0003] Ammonia is primarily used as a fuel in internal combustion engines through direct injection. This involves injecting ammonia into the cylinder as a high-pressure liquid, where it burns using a diffusion combustion method similar to that of traditional diesel engines. Compared to traditional internal combustion engines, this method achieves higher combustion efficiency, a higher ammonia fuel replacement rate, and lower nitrogen oxide and unburned ammonia emissions.

[0004] However, due to the extremely high volatility of ammonia, the current high-pressure direct injection diffusion combustion method of liquid ammonia in the cylinder cannot provide a stable and reliable liquid ammonia high-pressure injection system. The internal pressure of fuel storage materials such as liquid ammonia storage tanks and buffer tanks is unstable, and the liquid ammonia fuel is likely to vaporize, thereby affecting the working efficiency of the internal combustion engine. Summary of the Invention

[0005] In view of this, the present disclosure provides a control method for high-pressure direct injection of liquid ammonia and an ammonia fuel supply system.

[0006] According to one aspect of the present disclosure, a control method for high-pressure direct injection of liquid ammonia is provided, which is applied to an ammonia fuel supply system. The ammonia fuel supply system includes a liquid ammonia storage module and a high-pressure injection module. The liquid ammonia storage module includes a nitrogen source at a first pressure, a liquid ammonia storage tank at a second pressure, and a liquid ammonia buffer tank at a third pressure. The method includes:

[0007] The liquid level gauge on the liquid ammonia buffer tank is used to measure the liquid ammonia level in the liquid ammonia buffer tank in real time;

[0008] When the liquid level height does not meet the preset height range, the working state of the solenoid valve is controlled to adjust the injection amount of nitrogen from the nitrogen source into the liquid ammonia storage tank, wherein the injection amount of nitrogen can change the pressure difference between the liquid ammonia storage tank and the liquid ammonia buffer tank, thereby changing the speed at which liquid ammonia in the liquid ammonia storage tank is injected into the liquid ammonia buffer tank;

[0009] When the liquid level is within the preset range, the liquid ammonia in the liquid ammonia buffer tank is pumped to the high-pressure injection module according to the preset supply volume;

[0010] The high-pressure injection module injects a preset amount of liquid ammonia into the engine cylinder for combustion.

[0011] According to an embodiment of the present disclosure, the control method of liquid ammonia high-pressure direct injection further includes:

[0012] Before using the ammonia fuel supply system, the nitrogen in the nitrogen source is injected into the liquid ammonia storage tank separately or injected into the liquid ammonia buffer tank and the liquid ammonia storage tank simultaneously, so that the gas pressure of the liquid ammonia storage tank is the second gas pressure and / or the gas pressure of the liquid ammonia buffer tank is the third gas pressure, so that the liquid ammonia in the liquid ammonia storage tank is always in liquid state during the process of being injected into the liquid ammonia buffer tank.

[0013] According to an embodiment of the present disclosure, the control method of liquid ammonia high-pressure direct injection further includes:

[0014] When the pressure difference does not meet the pressure difference threshold, the amount of nitrogen in the liquid ammonia buffer tank and / or the liquid ammonia storage tank is adjusted.

[0015] According to an embodiment of the present disclosure, the pressure difference threshold includes a lower pressure difference threshold and an upper pressure difference threshold;

[0016] Wherein, when the pressure difference does not meet the pressure difference threshold, adjusting the amount of nitrogen in the liquid ammonia buffer tank and / or the liquid ammonia storage tank includes:

[0017] When the pressure difference is greater than the upper limit of the pressure difference threshold, the nitrogen in the liquid ammonia storage tank is discharged according to the preset discharge volume;

[0018] When the pressure difference is less than the lower limit of the pressure difference threshold, the nitrogen in the liquid ammonia buffer tank is discharged according to the preset discharge volume.

[0019] According to an embodiment of the present disclosure, the pressure difference threshold includes a lower pressure difference threshold and an upper pressure difference threshold;

[0020] Wherein, when the pressure difference does not meet the pressure difference threshold, adjusting the amount of nitrogen in the liquid ammonia buffer tank and / or the liquid ammonia storage tank includes:

[0021] When the pressure difference is greater than the upper limit of the pressure difference threshold, the nitrogen in the nitrogen source is injected into the liquid ammonia buffer tank according to the preset injection amount;

[0022] When the pressure difference is less than the lower limit of the pressure difference threshold, the nitrogen in the nitrogen source is injected into the liquid ammonia storage tank according to the preset injection amount.

[0023] According to an embodiment of the present disclosure, the ammonia fuel supply system for high-pressure direct injection of liquid ammonia further includes: a reflux cooling module;

[0024] The method also includes:

[0025] The reflux cooling module is used to treat the ammonia gas overflowing from the high-pressure injection module to obtain recovered liquid ammonia;

[0026] Injecting the recovered liquid ammonia into the liquid ammonia buffer tank;

[0027] Wherein, the reflux cooling module includes a reflux cooler;

[0028] The process of using a reflux cooling module to process ammonia gas overflowing from the high-pressure injection module to obtain recovered liquid ammonia includes:

[0029] The ammonia gas at the third pressure overflowing from the high-pressure injection module is cooled by a reflux cooler to obtain recovered liquid ammonia at the third pressure.

[0030] According to an embodiment of the present disclosure, a high-pressure injection module includes a common rail and an injector;

[0031] The high-pressure injection module injects a preset amount of liquid ammonia into the engine cylinder for combustion and work, including:

[0032] The common rail pipe is used to stabilize the pressure of the liquid ammonia output from the liquid ammonia buffer tank to obtain the stabilized liquid ammonia;

[0033] The common rail pipe delivers the stabilized liquid ammonia to the injector;

[0034] The fuel injector injects the preset supply amount of liquid ammonia into the engine cylinder for combustion and work, and / or ammonia gas overflowing from the fuel injector is recycled by a cooling module for treatment.

[0035] According to an embodiment of the present disclosure, the ammonia fuel supply system for high-pressure direct injection of liquid ammonia further includes: a liquid ammonia boosting module;

[0036] The liquid ammonia in the liquid ammonia buffer tank is pumped into the high-pressure injection module in the following manner:

[0037] Using the liquid ammonia boosting module to pressurize the liquid ammonia output from the liquid ammonia buffer tank to obtain liquid ammonia at a fourth pressure;

[0038] The liquid ammonia at the fourth pressure is delivered to the high-pressure injection module.

[0039] According to an embodiment of the present disclosure, the liquid ammonia boosting module includes a compressor, a controller, and a gas-liquid boosting pump;

[0040] The liquid ammonia boosting module is used to pressurize the liquid ammonia output from the liquid ammonia buffer tank to obtain liquid ammonia at the fourth pressure, including:

[0041] Under the control of the controller, the compressor delivers compressed air to the gas-liquid booster pump;

[0042] Compressed air is used to drive the gas-liquid booster pump to operate, so that the gas-liquid booster pump pressurizes the liquid ammonia output from the liquid ammonia buffer tank to obtain liquid ammonia at the fourth pressure.

[0043] Another aspect of the present disclosure provides an ammonia fuel supply system for high-pressure direct injection of liquid ammonia, comprising:

[0044] Liquid ammonia storage module, including:

[0045] a nitrogen source storing nitrogen at a first pressure;

[0046] a liquid ammonia storage tank connected to a nitrogen source via a pipeline provided with a solenoid valve, wherein the liquid ammonia storage tank stores liquid ammonia at a second pressure;

[0047] a liquid ammonia buffer tank, connected to the nitrogen source and the liquid ammonia storage tank through pipelines, wherein the gas pressure of the liquid ammonia buffer tank is the third gas pressure;

[0048] Among them, the liquid ammonia buffer tank is provided with a liquid level gauge, which is constructed as follows:

[0049] Measure the liquid ammonia level in the liquid ammonia buffer tank;

[0050] When the liquid level height does not meet the preset height range, the working state of the solenoid valve is controlled to adjust the injection amount of nitrogen from the nitrogen source into the liquid ammonia storage tank, wherein the injection amount of nitrogen can change the pressure difference between the liquid ammonia storage tank and the liquid ammonia buffer tank, thereby changing the speed at which liquid ammonia in the liquid ammonia storage tank is injected into the liquid ammonia buffer tank;

[0051] The liquid ammonia buffer tank is used to pump the liquid ammonia in the liquid ammonia buffer tank to the high-pressure injection module according to the preset supply volume when the liquid level height is within the preset height range;

[0052] The high-pressure injection module is configured to inject a preset supply amount of liquid ammonia into the engine cylinder for combustion.

[0053] According to an embodiment of the present disclosure, the liquid level height of the liquid ammonia in the liquid ammonia buffer tank is monitored in real time by a liquid level gauge on the liquid ammonia buffer tank. When the liquid level height does not meet the preset height range, the working state of the solenoid valve is controlled to adjust the injection amount of nitrogen in the nitrogen source into the liquid ammonia storage tank, so that the pressure difference between the liquid ammonia storage tank and the liquid ammonia buffer tank remains constant, so that the liquid ammonia inside the liquid ammonia buffer tank and the liquid ammonia output to the high-pressure injection module are always kept liquefied, thereby achieving the stability of the liquid ammonia output, and indirectly improving the working efficiency of the internal combustion engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a flow chart of a liquid ammonia high-pressure direct injection control method according to an embodiment of the present disclosure;

[0055] Figure 2 For application Figure 1 A schematic diagram of the structural composition of the ammonia fuel supply system of the method;

[0056] Figure 3 This is a schematic diagram of the structure of the reflux cooling module according to an embodiment of the present disclosure;

[0057] Figure 4 This is a schematic diagram of the structure of a high-pressure injection module according to an embodiment of the present disclosure;

[0058] Figure 5 This is a schematic diagram of the structure of the liquid ammonia boosting module according to an embodiment of the present disclosure;

[0059] Figure 6 To distinguish from Figure 2 Schematic diagram of the structural composition of the ammonia fuel supply system of an embodiment.

[0060] In the above drawings, the meanings of the reference numerals are:

[0061] 100-Liquid ammonia storage module;

[0062] 101- high-pressure ammonia source;

[0063] 102~103-pressure reducing valve;

[0064] 104- solenoid valve;

[0065] 105-pressure relief valve;

[0066] 106-Liquid ammonia storage tank;

[0067] 107-control valve;

[0068] 108-Liquid ammonia buffer tank;

[0069] 109-Liquid level gauge;

[0070] 110-pressure relief valve;

[0071] 200- reflux cooling module;

[0072] 201- reflux cooler;

[0073] 202~205-control valve;

[0074] 300-high pressure injection module;

[0075] 301-common rail pipe;

[0076] 302-injector;

[0077] 400-Liquid ammonia booster module;

[0078] 401-compressor;

[0079] 402-gas-liquid booster pump;

[0080] 403-Solenoid valve;

[0081] 404-Controller; and

[0082] 405-Control valve. Implementation Method

[0083] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the detailed description below, for ease of explanation, many details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0084] The terms used herein are merely for describing the embodiments and are not intended to limit the present disclosure. The terms "comprise," "include," etc. used herein indicate the presence of the features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0085] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0086] When expressions such as "at least one of A, B and C, etc." are used, they should generally be interpreted in accordance with the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0087] The following will describe the embodiments of the present disclosure in detail in conjunction with the accompanying drawings to fully describe the technical solution of the present disclosure. This embodiment is implemented on the premise of the technical solution of the present disclosure, and a detailed implementation method and operation process are given, but the scope of protection of the present disclosure is not limited to the following embodiments.

[0088] Figure 1 A flow chart of a liquid ammonia high-pressure direct injection control method according to an embodiment of the present disclosure is schematically shown.

[0089] like Figure 1 As shown, the control method of high-pressure direct injection of liquid ammonia is applied to an ammonia fuel supply system, the ammonia fuel supply system includes a liquid ammonia storage module and a high-pressure injection module, the liquid ammonia storage module includes a nitrogen source of a first pressure, a liquid ammonia storage tank of a second pressure and a liquid ammonia buffer tank of a third pressure, and the method includes operations S101 to S103.

[0090] In operation S101 , the liquid level of the liquid ammonia in the liquid ammonia buffer tank is measured in real time by using a liquid level gauge on the liquid ammonia buffer tank.

[0091] In operation S102, when the liquid level height does not meet the preset height range, the working state of the solenoid valve is controlled to adjust the injection amount of nitrogen in the nitrogen source into the liquid ammonia storage tank, wherein the injection amount of nitrogen can change the pressure difference between the liquid ammonia storage tank and the liquid ammonia buffer tank to change the speed at which liquid ammonia in the liquid ammonia storage tank is injected into the liquid ammonia buffer tank.

[0092] In operation S103 , when the liquid level is within a preset range, the liquid ammonia in the liquid ammonia buffer tank is pumped to the high-pressure injection module according to a preset supply volume.

[0093] In operation S104 , the high-pressure injection module injects a preset supply amount of liquid ammonia into the engine cylinder for combustion.

[0094] Figure 2 Schematically illustrates the application of the embodiment of the present disclosure Figure 1 Schematic diagram of the structural composition of the ammonia fuel supply system of the method.

[0095] like Figure 2 As shown, in the liquid ammonia storage module 100, the nitrogen source 101 stores nitrogen at a first pressure (such as 10 MPa) for providing high-pressure nitrogen to the outside. Figure 2 The nitrogen source 101 is shown in the shape of a tank, but it should be understood that the illustrated components do not limit the shape of the components. In some embodiments of the present disclosure, the nitrogen source 101 can be any component that can provide high-pressure nitrogen, such as a storage tank, a box, or a gas bag.

[0096] Liquid ammonia storage tank 106 maintains a second pressure (e.g., 2.5 MPa), allowing for a certain amount of liquid ammonia to be stored in advance for use as liquid ammonia fuel. Liquid ammonia buffer tank 108 maintains a third pressure (e.g., 2.0 MPa) for compressed storage and transfer of liquid ammonia. Similar to nitrogen source 101, the shapes of liquid ammonia storage tank 106 and liquid ammonia buffer tank 108 are not restricted and can be adapted to meet specific needs.

[0097] It should be understood that there is no upper limit on the first air pressure, the second air pressure, and the third air pressure. This embodiment provides three values ​​of 10 MPa, 2 MPa, and 2.5 MPa, which are only used for examples and to illustrate the concept of pressure difference. Depending on actual usage, any air pressure value that meets the requirements of the method can be selected.

[0098] The liquid level meter 109 is installed in the liquid ammonia buffer tank 108 to measure the liquid level in the tank in real time. The liquid level meter 109 can be any device capable of measuring the liquid level, such as a capacitive sensor, an ultrasonic sensor, a pressure sensor, a float sensor, etc. (for example only).

[0099] The high-pressure injection module 300 is connected to the liquid ammonia storage module 100 and injects a preset amount of liquid ammonia into the engine cylinder for combustion and work.

[0100] In this embodiment, the amount of nitrogen injected into the liquid ammonia storage tank 106 and the liquid ammonia buffer tank 108 is controlled by the solenoid valve 104. It should be understood that the solenoid valve 104 in this embodiment is merely an example and can be replaced with various system-controlled devices that can change the flow of the pipeline, such as a pneumatic valve, an electric butterfly valve, or an electric ball valve, depending on actual usage.

[0101] It should be understood that Figure 2 The number of nitrogen sources, liquid ammonia storage tanks, liquid ammonia buffer tanks, liquid level gauges, and solenoid valves is merely illustrative. Any number of nitrogen sources, liquid ammonia storage tanks, liquid ammonia buffer tanks, liquid level gauges, and solenoid valves may be provided as needed.

[0102] During the operation of the system of this embodiment, the liquid level meter 109 measures the liquid ammonia level in the liquid ammonia buffer tank 108 in real time, and compares and analyzes the measured result with the preset height range to determine whether to pump the liquid ammonia into the subsequent module. For example:

[0103] If the measured liquid level in the tank exceeds the preset range, the opening of solenoid valve 104 is adjusted to control the amount of nitrogen injected into liquid ammonia storage tank 106. This changes the pressure differential between liquid ammonia storage tank 106 and liquid ammonia buffer tank 108, thereby adjusting the rate at which liquid ammonia is injected into liquid ammonia buffer tank 108 and the liquid level in the tank. After adjusting the liquid ammonia level in liquid ammonia buffer tank 108, the level gauge remeasures the liquid level in the tank. If the measured liquid level in the tank does not exceed the preset range, the liquid ammonia in liquid ammonia buffer tank 108 is pumped into the high-pressure injection module at the preset supply rate.

[0104] It should be understood that the preset height range includes: a preset lower limit and a preset upper limit. When the measured value of the liquid level in the tank is less than the preset lower limit, i.e., the amount of liquid ammonia in the tank is too low, the opening of the solenoid valve 104 is increased, thereby increasing the speed at which liquid ammonia is injected into the liquid ammonia buffer tank 108 and raising the liquid level in the tank. When the measured value is greater than the preset upper limit, i.e., the amount of liquid ammonia in the tank is excessive, the opening of the solenoid valve 104 is decreased, thereby slowing the speed at which liquid ammonia is injected into the liquid ammonia buffer tank 108 and lowering the liquid level in the tank. Ultimately, the liquid ammonia level in the liquid ammonia buffer tank 108 is maintained within a stable range, thereby ensuring stable output of liquid ammonia to the high-pressure injection module.

[0105] According to an embodiment of the present disclosure, the liquid level height of the liquid ammonia in the liquid ammonia buffer tank 108 is monitored in real time by the liquid level gauge 109 on the liquid ammonia buffer tank 108. When the liquid level height does not meet the preset height range, the working state of the solenoid valve 104 is controlled to adjust the injection amount of nitrogen in the nitrogen source 101 into the liquid ammonia storage tank 106, so that the pressure difference between the liquid ammonia storage tank 106 and the liquid ammonia buffer tank 108 remains constant, so that the liquid ammonia inside the liquid ammonia buffer tank 108 and the liquid ammonia output to the high-pressure injection module are always kept liquefied, thereby achieving the stability of the liquid ammonia output, and indirectly improving the working efficiency of the internal combustion engine.

[0106] According to an embodiment of the present disclosure, before using the ammonia fuel supply system, the nitrogen in the nitrogen source 101 is injected into the liquid ammonia storage tank 106 separately or simultaneously into the liquid ammonia buffer tank 108 and the liquid ammonia storage tank 106, so that the gas pressure of the liquid ammonia storage tank 106 is the second gas pressure and / or the gas pressure of the liquid ammonia buffer tank 108 is the third gas pressure, so that the liquid ammonia in the liquid ammonia storage tank 106 is always in a liquid state during the process of being injected into the liquid ammonia buffer tank 108.

[0107] Specifically, before filling liquid ammonia buffer tank 108 with liquid ammonia, high-pressure nitrogen from nitrogen source 101 is injected into liquid ammonia storage tank 106 and liquid ammonia buffer tank 108, respectively, to establish a second pressure and a third pressure that are higher than the ammonia saturation pressure. After this filling phase, if liquid level gauge 109 detects that the liquid level in liquid ammonia buffer tank 108 is within a preset range, a preset supply of relatively stable liquid ammonia fuel is pumped into the high-pressure injection module, which then injects it into the engine cylinders for combustion.

[0108] In this embodiment, nitrogen is used to regulate the internal pressure of the two tanks. This ensures that the liquid ammonia in liquid ammonia storage tank 106 and liquid ammonia buffer tank 108 remains liquid and does not vaporize before and during injection. It should be noted that nitrogen injection into liquid ammonia storage tank 106 and liquid ammonia buffer tank 108 can be performed simultaneously, thereby rapidly regulating the tank pressure and facilitating rapid filling of liquid ammonia fuel.

[0109] According to an embodiment of the present disclosure, the injection of high-pressure nitrogen forms a second air pressure and a third air pressure between the liquid ammonia storage tank 106 and the liquid ammonia buffer tank 108. Due to the pressure difference between the second air pressure and the third air pressure, the liquid ammonia in the liquid ammonia storage tank 106 is input into the liquid ammonia buffer tank 108 to realize the filling of liquid ammonia from the liquid ammonia storage tank 106 to the liquid ammonia buffer tank 108.

[0110] During system operation, when the pressure difference between the second air pressure and the third air pressure is too large, the speed at which liquid ammonia is injected into the liquid ammonia buffer tank 108 is faster, and the liquid level in the tank is likely to exceed the preset upper limit; when the pressure difference is too small, the speed at which liquid ammonia is injected into the liquid ammonia buffer tank 108 is slower, and the liquid level in the tank is likely to exceed the preset lower limit, making it impossible to provide a stable supply of liquid ammonia for the high-pressure injection module.

[0111] The embodiment of the present disclosure sets a pressure difference threshold. When the pressure difference does not meet the pressure difference threshold, the amount of nitrogen in the liquid ammonia buffer tank 108 and / or the liquid ammonia storage tank 106 is adjusted so that the pressure difference inside the two tanks meets the pressure difference threshold, thereby ensuring a continuous and stable supply of liquid ammonia.

[0112] According to an embodiment of the present disclosure, the pressure difference threshold includes: an upper pressure difference threshold and a lower pressure difference threshold.

[0113] Wherein, when the pressure difference does not meet the pressure difference threshold, adjusting the amount of nitrogen in the liquid ammonia buffer tank 108 and / or the liquid ammonia storage tank 106 includes:

[0114] When the pressure difference is greater than the upper limit of the pressure difference threshold, the nitrogen in the liquid ammonia storage tank 106 is discharged according to the preset discharge volume.

[0115] When the pressure difference is less than the lower limit of the pressure difference threshold, the nitrogen in the liquid ammonia buffer tank 108 is discharged according to the preset discharge volume.

[0116] Specifically, in an embodiment of the present disclosure, when the pressure difference between the second air pressure and the third air pressure is greater than the upper limit of the pressure difference threshold, excess nitrogen in the liquid ammonia storage tank 106 is discharged through the pressure relief valve 105 to reduce the pressure difference between the two tanks and slow down the speed of liquid ammonia injection into the liquid ammonia buffer tank 108.

[0117] When the pressure difference between the second air pressure and the third air pressure is less than the lower limit of the pressure difference threshold, excess nitrogen in the liquid ammonia buffer tank 108 is discharged through the pressure relief valve 110 to increase the pressure difference between the two tanks and speed up the injection of liquid ammonia into the liquid ammonia buffer tank 108.

[0118] It should be understood that the use of pressure relief valves 105 and 110 in this embodiment is only an example, and the type of pressure relief device is not limited. It can be a spring-type pressure relief valve, a lever-type pressure relief valve, a pilot-type pressure relief valve, or other devices that can relieve excess pressure.

[0119] Furthermore, the connection locations of pressure relief valves 105 and 110 are not fixed; the internal pressures of liquid ammonia storage tank 106 and liquid ammonia buffer tank 108 can be adjusted. In some embodiments of the present disclosure, pressure relief valve 105 can be installed on the nitrogen inlet pipe or the top of the liquid ammonia storage tank 106. Similarly, pressure relief valve 110 can be installed on the nitrogen inlet pipe or the top of the liquid ammonia buffer tank 108.

[0120] The embodiment of the present disclosure adjusts the internal air pressure of the liquid ammonia storage tank 106 and the liquid ammonia buffer tank 108 by means of pressure relief, thereby increasing or decreasing the pressure difference between the two tanks to change the speed at which liquid ammonia is charged into the liquid ammonia buffer tank 108, thereby maintaining the liquid level height in the liquid ammonia buffer tank 108 stable.

[0121] According to an embodiment of the present disclosure, the pressure difference threshold includes: a lower pressure difference threshold and an upper pressure difference threshold.

[0122] Wherein, when the pressure difference does not meet the pressure difference threshold, adjusting the amount of nitrogen in the liquid ammonia buffer tank 108 and / or the liquid ammonia storage tank 106 includes the following operations:

[0123] When the pressure difference is greater than the upper limit of the pressure difference threshold, the nitrogen in the nitrogen source 101 is injected into the liquid ammonia buffer tank 108 according to a preset injection amount.

[0124] When the pressure difference is less than the lower limit of the pressure difference threshold, the nitrogen in the nitrogen source 101 is injected into the liquid ammonia storage tank 106 according to a preset injection amount.

[0125] Specifically, in an embodiment of the present disclosure, when the pressure difference between the second air pressure and the third air pressure is greater than the upper limit of the pressure difference threshold, the difference between the actual pressure difference value and the upper limit of the pressure difference threshold is calculated to obtain the amount of nitrogen to be injected into the liquid ammonia buffer tank 108, and the nitrogen in the nitrogen source 101 is injected into the liquid ammonia buffer tank 108 according to the calculated preset injection amount, so as to reduce the pressure difference between the two tanks and slow down the speed of liquid ammonia injection into the liquid ammonia buffer tank 108.

[0126] When the pressure difference between the second air pressure and the third air pressure is less than the lower limit of the pressure difference threshold, the difference between the actual pressure difference value and the lower limit of the pressure difference threshold is calculated to obtain the amount of nitrogen to be injected into the liquid ammonia storage tank 106, and the nitrogen in the nitrogen source 101 is injected into the liquid ammonia storage tank 106 according to the calculated preset injection amount to increase the pressure difference between the two tanks and speed up the injection of liquid ammonia into the liquid ammonia buffer tank 108.

[0127] In this embodiment, the internal pressure of the liquid ammonia storage tank 106 and the liquid ammonia buffer tank 108 is adjusted by adding a preset amount of nitrogen, thereby increasing or decreasing the pressure difference between the two tanks to change the speed at which liquid ammonia is charged into the liquid ammonia buffer tank 108, thereby maintaining a stable liquid level in the liquid ammonia buffer tank 108. The addition of nitrogen according to the preset amount can be achieved by various quantitative methods, such as installing an electromagnetic flowmeter, a mass flowmeter, a gas metering valve, or other devices that can quantitatively represent the amount of fluid.

[0128] According to an embodiment of the present disclosure, the high-pressure injection module injects liquid ammonia into the engine cylinder for combustion and work. During the actual fuel injection process, due to the structural characteristics of the high-pressure injector (i.e., the injector 302 of the present disclosure) (the injection pressure is greater than 35 MPa), when the high-pressure injector is working, part of the ammonia fuel will flow back to the low-pressure end in the form of high-temperature gas.

[0129] The embodiments of the present disclosure disclose a control method for high-pressure direct injection of liquid ammonia, which is applied to an ammonia fuel supply system. The system further includes a reflux cooling module. The control method for high-pressure direct injection of liquid ammonia also includes the following operations:

[0130] The ammonia gas overflowed from the high-pressure injection module is processed by the reflux cooling module to obtain recovered liquid ammonia, which is then injected into the liquid ammonia buffer tank 108 .

[0131] Wherein, the reflux cooling module includes a reflux cooler.

[0132] The reflux cooling module is used to process the ammonia gas overflowing from the high-pressure injection module to obtain recovered liquid ammonia, including the following operations:

[0133] The ammonia gas at the third pressure overflowing from the high-pressure injection module is cooled by a reflux cooler to obtain recovered liquid ammonia at the third pressure.

[0134] The control method for high-pressure direct injection of liquid ammonia provided in the embodiment of the present disclosure utilizes a reflux cooling module to liquefy the high-temperature ammonia gas overflowing from the high-pressure injection module and injects the liquefied gas into the liquid ammonia buffer tank 108, thereby realizing the recycling of ammonia fuel.

[0135] Among them, the reflux cooling module can use the reflux cooler to cool the overflowing high-temperature ammonia. Figure 3 The schematic diagram of the structural composition of the reflux cooling module according to an embodiment of the present disclosure is shown schematically.

[0136] like Figure 3 As shown, high-temperature ammonia gas overflowing from the high-pressure injection module enters the reflux cooler 201 through a pipeline. After being cooled by circulating cooling water, the gaseous high-temperature ammonia gas is converted back into room-temperature liquid ammonia and flows back into the liquid ammonia buffer tank 108. The liquid ammonia buffer tank, the high-pressure injection module, and the reflux cooling module form a closed loop. The liquid ammonia in the liquid ammonia buffer tank, the overflowing ammonia gas, and the cooled liquid ammonia are all at the same pressure (i.e., the third pressure).

[0137] The reflux cooler 201 of the reflux cooling module 200 utilizes circulating cooling water for cooling and operates independently of the ammonia fuel. The circulating cooling water does not directly participate in the circulation of the ammonia fuel, thereby ensuring the purity of the ammonia fuel.

[0138] It should be understood that the circulating cooling water used in this embodiment is only used to illustrate the cooling effect of the reflux cooling module. There is no restriction on the cooling method of this module. Depending on actual usage, it can also be replaced with other methods that can ensure the cooling effect (such as air cooling, etc.).

[0139] In this embodiment, the cooling function of the reflux cooling module 200 and the reflux cooler 201 is utilized to realize the recycling of ammonia fuel, thereby forming a stable liquid ammonia closed cycle to ensure the normal and stable operation of the system.

[0140] According to an embodiment of the present invention, when the reflux cooling module 200 cannot provide sufficient cooling effect (such as the reflux flow is too large, the liquid ammonia is overheated, etc.), the excess high-temperature ammonia can be directly discharged through the exhaust pipe, so that the cooled liquid ammonia has a relatively stable temperature, ensuring the temperature of the fuel in the liquid ammonia buffer tank 108 is stable.

[0141] According to an embodiment of the present disclosure, a preset supply amount of liquid ammonia outputted from a liquid ammonia buffer tank is injected by a high-pressure injection module into an engine cylinder for combustion and work. Due to the strong volatility of ammonia and the relatively high pressure of liquid ammonia outputted from the liquid ammonia buffer tank, part of the liquid ammonia fuel will overflow from the module in a gaseous form.

[0142] The embodiments of the present disclosure disclose a control method for high-pressure direct injection of liquid ammonia, which is applied to an ammonia fuel supply system. The high-pressure injection module of the system includes a common rail and an injector.

[0143] The high-pressure injection module injects a preset amount of liquid ammonia into the engine cylinder for combustion, including the following operations:

[0144] The common rail stabilizes the pressure of liquid ammonia output from the liquid ammonia buffer tank 108 to produce stabilized liquid ammonia. The common rail delivers the stabilized liquid ammonia to the injectors. The injectors inject the stabilized liquid ammonia into the engine cylinders for combustion and / or ammonia gas overflowing the injectors is recycled to the cooling module for recovery.

[0145] Figure 4 The schematic diagram of the structural composition of the high-pressure injection module according to an embodiment of the present disclosure is shown schematically.

[0146] like Figure 4 As shown, after the liquid ammonia buffer tank 108 outputs the liquid ammonia fuel, the common rail 301 stores the high-pressure liquid ammonia fuel output from the liquid ammonia buffer tank 108, stabilizes the pressure, and delivers the stabilized liquid ammonia to the injector 302. Within a specified timeframe, the injector 302 injects a predetermined amount of liquid ammonia at the required pressure into the engine combustion chamber, causing combustion and generating work. Unburned, volatilized ammonia can overflow from the top of the injector 302 for subsequent cooling and recovery.

[0147] It should be noted that the injector 302 in the high pressure injection module 300 may have multiple ( Figure 4 (not shown) to improve the power and combustion efficiency of the engine.

[0148] The control method for high-pressure direct injection of liquid ammonia provided in the embodiment of the present disclosure utilizes the common rail pipe 301 and the injector 302 to stabilize the pressure of the liquid ammonia, and then injects it into the engine cylinder for combustion and work, thereby reducing the overflow of ammonia. The high-temperature ammonia that is not completely burned can be recovered after overflowing through the injector 302, thereby improving the utilization rate of the fuel and reducing fuel loss.

[0149] According to an embodiment of the present disclosure, when the rail pressure in the common rail pipe 301 is too high, the pressure relief valve in the exhaust pipe opens to release some of the pressure, thereby maintaining a stable rail pressure. Similarly, the pressure relief valve in this embodiment is merely an example and can be replaced with various devices that can achieve a pressure relief function depending on actual use.

[0150] According to an embodiment of the present disclosure, the opening and closing of the injector in the above-mentioned high-pressure injection module is controlled by an electronic control system (ECU) to realize actions such as starting and ending injection of ammonia fuel.

[0151] According to an embodiment of the present disclosure, the injector in the above-mentioned high-pressure injection module is installed inside the engine cylinder block, located at the top of the engine cylinder, to ensure that high-pressure liquid ammonia is sprayed into the engine cylinder (combustion chamber).

[0152] According to an embodiment of the present disclosure, when the control method of high-pressure direct injection of liquid ammonia and the corresponding liquid ammonia supply system are applied to a large internal combustion engine (i.e., the engine of the present disclosure), the high-pressure injection module 300 is used to inject the liquid ammonia of the third pressure output by the liquid ammonia buffer tank 108 into the engine cylinder for combustion and work. However, the liquid ammonia of the third pressure may still not meet the use requirements of a large in-cylinder high-pressure direct injection compression ignition engine.

[0153] An embodiment of the present disclosure discloses an ammonia fuel supply system that applies a control method for high-pressure direct injection of liquid ammonia. The system includes a liquid ammonia boosting module.

[0154] The liquid ammonia in the liquid ammonia buffer tank 108 is pumped into the high-pressure injection module 300 in the following manner:

[0155] The liquid ammonia boosting module is used to pressurize the liquid ammonia output from the liquid ammonia buffer tank 108 to obtain liquid ammonia at a fourth pressure.

[0156] The liquid ammonia at the fourth pressure is delivered to the high-pressure injection module 300 .

[0157] The control method for high-pressure direct injection of liquid ammonia provided in the embodiment of the present disclosure utilizes a liquid ammonia boosting module to further pressurize the third-pressure liquid ammonia output from the liquid ammonia storage module, and delivers the pressurized (fourth-pressure) liquid ammonia to the high-pressure injection module 300, thereby meeting the use requirements of large-scale in-cylinder high-pressure direct injection compression ignition engines.

[0158] According to an embodiment of the present disclosure, an ammonia fuel supply system applying a control method for high-pressure direct injection of liquid ammonia is disclosed. The system includes: a liquid ammonia boosting module.

[0159] Among them, the liquid ammonia boosting module includes: a compressor, a controller and a gas-liquid boosting pump.

[0160] The liquid ammonia boosting module is used to pressurize the liquid ammonia output from the liquid ammonia buffer tank 108 to obtain liquid ammonia at the fourth pressure, including:

[0161] Under the control of the controller, the compressor delivers compressed air to the gas-liquid booster pump.

[0162] The compressed air is used to drive the gas-liquid booster pump to operate, so that the gas-liquid booster pump pressurizes the liquid ammonia output from the liquid ammonia buffer tank 108 to obtain liquid ammonia at the fourth pressure.

[0163] Figure 5 The figure schematically shows the composition of the liquid ammonia boosting module of the ammonia fuel supply system according to the embodiment of the present disclosure.

[0164] like Figure 5 As shown, during the operation of the liquid ammonia boosting module, the compressor 401 compresses the air, the controller 404 controls the pressure of the compressed air, and transmits it to the gas-liquid boosting pump 402 to drive the operation of the gas-liquid boosting pump 402; the liquid ammonia in the liquid ammonia storage module enters the gas-liquid boosting pump 402, and is further pressurized under the drive of the compressed air, and enters the high-pressure injection module 300 after reaching the set pressure (i.e., the fourth air pressure).

[0165] It should be understood that the compressed air driving method of the gas-liquid booster pump 402 is only an example. According to actual usage, the gas-liquid booster pump 402 can also be replaced by other driving devices that meet the boosting requirements, such as an electric booster pump, a chlorine booster pump, etc.

[0166] In this embodiment, the gas-liquid boost pump 402 of the liquid ammonia boost module 400 uses compressed air to drive and pressurize, which can effectively prevent ammonia corrosion and has strong wear resistance; the compressed air and liquid ammonia operate independently, and the compressed air does not directly participate in the circulation of liquid ammonia to ensure the purity of the liquid ammonia; by pressurizing the liquid ammonia output from the liquid ammonia buffer tank 108, the use requirements of large-scale in-cylinder high-pressure direct injection compression ignition engines are met.

[0167] According to an embodiment of the present disclosure, the gas-liquid booster pump 402 can boost the ammonia fuel to a high-pressure state of more than 50 MPa through proportional boosting, thereby realizing a high-pressure injection process of liquid ammonia near the top dead center of compression of the engine and achieving direct injection diffusion combustion of liquid ammonia.

[0168] According to an embodiment of the present disclosure, an ammonia fuel supply system for high-pressure direct injection of liquid ammonia is disclosed, comprising:

[0169] The liquid ammonia storage module includes a nitrogen source storing nitrogen at a first pressure; a liquid ammonia storage tank connected to the nitrogen source via a pipeline equipped with a solenoid valve, wherein the liquid ammonia storage tank stores liquid ammonia at a second pressure; and a liquid ammonia buffer tank connected to the nitrogen source and the liquid ammonia storage tank via pipelines, wherein the liquid ammonia buffer tank is at a third pressure.

[0170] The liquid ammonia buffer tank is provided with a liquid level gauge, which is configured to measure the liquid level of the liquid ammonia in the liquid ammonia buffer tank.

[0171] When the liquid level height does not meet the preset height range, the working state of the solenoid valve is controlled to adjust the injection amount of nitrogen in the nitrogen source into the liquid ammonia storage tank, wherein the injection amount of nitrogen can change the pressure difference between the liquid ammonia storage tank and the liquid ammonia buffer tank to change the speed at which liquid ammonia in the liquid ammonia storage tank is injected into the liquid ammonia buffer tank.

[0172] Among them, the liquid ammonia buffer tank is used to pump the liquid ammonia in the liquid ammonia buffer tank to the high-pressure injection module according to a preset supply amount when the liquid level height meets the preset height range.

[0173] The high-pressure injection module is configured to inject the preset supply amount of liquid ammonia into the engine cylinder for combustion and work.

[0174] Please refer to the system operation process Figure 2 , pressure reducing valve 102 is opened, and nitrogen at a first pressure from nitrogen source 101 is injected into liquid ammonia storage tank 106. This creates a second pressure in liquid ammonia storage tank 106, creating a pressure differential with the third pressure in liquid ammonia buffer tank 108. Under this pressure differential, the liquid ammonia in liquid ammonia storage tank 106 is fed into liquid ammonia buffer tank 108 through the bottom pipe. Liquid level meter 109 monitors the liquid ammonia level in the tank in real time. When the measured value falls within a preset range, liquid ammonia is quantitatively pumped into the high-pressure injection module. If the measured value does not fall within the preset range, the opening of solenoid valve 104 is controlled to adjust the amount of nitrogen injected into liquid ammonia storage tank 106, thereby changing the pressure differential between liquid ammonia storage tank 106 and liquid ammonia buffer tank 108 and the injection rate of liquid ammonia into liquid ammonia buffer tank 108, thereby controlling the liquid level in liquid ammonia buffer tank 108.

[0175] According to an embodiment of the present disclosure, the liquid level height of the liquid ammonia in the liquid ammonia buffer tank 108 is monitored in real time by the liquid level gauge 109 on the liquid ammonia buffer tank 108. When the liquid level height does not meet the preset height range, the working state of the solenoid valve 104 is controlled to adjust the injection amount of nitrogen in the nitrogen source 101 into the liquid ammonia storage tank 106, so that the pressure difference between the liquid ammonia storage tank 106 and the liquid ammonia buffer tank 108 remains constant, so that the liquid ammonia inside the liquid ammonia buffer tank 108 and the liquid ammonia output to the high-pressure injection module are always kept liquefied, thereby achieving the stability of the liquid ammonia output, and indirectly improving the working efficiency of the internal combustion engine.

[0176] Figure 6 The schematic diagram of the structural composition of the ammonia fuel supply system according to an embodiment of the present disclosure is schematically shown.

[0177] According to an embodiment of the present disclosure, the ammonia fuel supply system further includes: at least two pressure gauges ( Figure 6 (not shown), respectively arranged in the liquid ammonia storage tank 106 and the liquid ammonia buffer tank 108, at least two pressure gauges are configured to detect the pressure difference between the liquid ammonia storage tank 106 and the liquid ammonia buffer tank 108, and adjust the amount of nitrogen in the liquid ammonia buffer tank 108 and / or the liquid ammonia storage tank 106 when the pressure difference does not meet the pressure difference threshold.

[0178] According to an embodiment of the present disclosure, the ammonia fuel supply system further includes: an emptying pipe is provided on the liquid ammonia storage tank 106 and the liquid ammonia buffer tank 108, wherein the emptying pipe is used to discharge part of the nitrogen in the liquid ammonia storage tank 106 and the liquid ammonia buffer tank 108.

[0179] According to an embodiment of the present disclosure, the ammonia fuel supply system further includes: a control valve 107 provided on the pipeline between the liquid ammonia buffer tank 106 and the nitrogen source 101 , and the control valve is used to control the nitrogen in the nitrogen source 101 to be charged into the liquid ammonia buffer tank 108 .

[0180] According to an embodiment of the present disclosure, the ammonia fuel supply system further includes: a reflux cooling module 200, which is respectively connected to the high-pressure injection module 300 and the liquid ammonia buffer tank 108. The reflux cooling module 200 processes the ammonia gas overflowing from the high-pressure injection module 300 to obtain recovered liquid ammonia, and injects the recovered liquid ammonia into the liquid ammonia buffer tank 108.

[0181] According to an embodiment of the present disclosure, the reflux cooling module 200 of the ammonia fuel supply system includes: a reflux cooler 201, the input end of the reflux cooler 201 is connected to the overflow port of the high-pressure injection module 300, and the output end of the reflux cooler 201 is connected to the bottom of the liquid ammonia buffer tank 108. The reflux cooler 201 is used to cool and recover the overflowed ammonia gas.

[0182] According to an embodiment of the present disclosure, the high-pressure injection module 300 of the ammonia fuel supply system includes:

[0183] The common rail pipe 301 is connected to the liquid ammonia buffer tank 108 and is used to stabilize the pressure of the liquid ammonia output from the liquid ammonia buffer tank 108 .

[0184] The fuel injector 302 has an overflow port connected to the reflux cooling module 200 , and a fuel inlet of the fuel injector 302 is connected to the outlet of the common rail pipe 301 . The fuel injector 302 is used to inject liquid ammonia into the engine cylinder for combustion and work.

[0185] According to an embodiment of the present disclosure, the ammonia fuel supply system further includes: a liquid ammonia boosting module 400; the input end and the output end of the liquid ammonia boosting module 400 are respectively connected to the bottom of the liquid ammonia buffer tank 108 and the high-pressure injection module 300, and the liquid ammonia boosting module 400 is used to pressurize the liquid ammonia.

[0186] According to an embodiment of the present disclosure, the liquid ammonia boosting module 400 of the ammonia fuel supply system includes:

[0187] The compressor 401 is used to output compressed air.

[0188] The controller 404 is used to control the working state of the compressor 401 so that the compressor 401 outputs compressed air.

[0189] The gas-liquid booster pump 402 is driven by compressed air and is configured to pressurize the liquid ammonia output from the liquid ammonia buffer tank 108 .

[0190] It should be noted that the ammonia fuel supply system part in the embodiment of the present disclosure corresponds to the control method part of the liquid ammonia high-pressure direct injection in the embodiment of the present disclosure. The description of the ammonia fuel supply system part specifically refers to the control method part of the liquid ammonia high-pressure direct injection, which will not be repeated here.

[0191] The ammonia fuel supply system provided by the present disclosure can realize high-pressure direct injection of ammonia fuel into the cylinder, which helps to achieve stable ignition and efficient combustion of the ammonia fuel engine, thereby realizing efficient and clean utilization of ammonia fuel in the internal combustion engine; when the operating conditions suddenly change, the excess gas in the system can be fully or partially discharged through the emptying pipe, thereby improving the stability and reliability of the entire system.

[0192] Thus far, the embodiments of the present disclosure have been described in detail with reference to the accompanying drawings. It should be noted that any implementations not depicted or described in the drawings or the main body of the specification are known to those of ordinary skill in the art and are not described in detail. Furthermore, the terms "first" and "second" mentioned above are merely descriptions of the embodiments and are not intended to limit the scope of the present disclosure.

[0193] The embodiments of the present disclosure are described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Although each embodiment has been described separately above, this does not mean that the measures in each embodiment cannot be used in combination to advantage. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A control method for high-pressure direct injection of liquid ammonia, applied to an ammonia fuel supply system, wherein the ammonia fuel supply system includes a liquid ammonia storage module, a liquid ammonia boosting module, a high-pressure injection module, and a reflux cooling module. The liquid ammonia storage module includes a nitrogen source at a first pressure, a liquid ammonia storage tank at a second pressure, and a liquid ammonia buffer tank at a third pressure. The method includes: Using the liquid level gauge on the liquid ammonia buffer tank to measure the liquid level of the liquid ammonia in the liquid ammonia buffer tank in real time; When the liquid level height does not meet the preset height range, the working state of the solenoid valve is controlled to adjust the injection amount of nitrogen in the nitrogen source into the liquid ammonia storage tank, wherein the injection amount of the nitrogen can change the pressure difference between the liquid ammonia storage tank and the liquid ammonia buffer tank, so as to change the speed at which the liquid ammonia in the liquid ammonia storage tank is injected into the liquid ammonia buffer tank. When the pressure difference does not meet a pressure difference threshold, adjusting the amount of nitrogen in the liquid ammonia buffer tank and / or the liquid ammonia storage tank, wherein the pressure difference threshold includes a lower pressure difference threshold and an upper pressure difference threshold; When the pressure difference is greater than the upper limit of the pressure difference threshold, discharging the nitrogen in the liquid ammonia storage tank according to a preset discharge volume; When the pressure difference is less than the lower limit of the pressure difference threshold, discharging the nitrogen in the liquid ammonia buffer tank according to the preset discharge volume; When the liquid level is within the preset height range, the liquid ammonia in the liquid ammonia buffer tank is pressurized by the liquid ammonia boosting module, and the pressurized liquid ammonia is pumped to the high-pressure injection module according to a preset supply amount; The high-pressure injection module injects the preset amount of liquid ammonia into the engine cylinder for combustion and work. The reflux cooling module is then used to treat the ammonia gas overflowing from the high-pressure injection module to obtain recovered liquid ammonia, which is then injected into the liquid ammonia buffer tank.

2. The method according to claim 1, further comprising: Before using the ammonia fuel supply system, the nitrogen in the nitrogen source is injected into the liquid ammonia storage tank separately or simultaneously into the liquid ammonia buffer tank and the liquid ammonia storage tank, so that the gas pressure of the liquid ammonia storage tank is the second gas pressure and / or the gas pressure of the liquid ammonia buffer tank is the third gas pressure, so that the liquid ammonia in the liquid ammonia storage tank is always in a liquid state during the process of being injected into the liquid ammonia buffer tank.

3. The method according to claim 1, wherein the pressure difference threshold comprises a lower pressure difference threshold and an upper pressure difference threshold; in, When the pressure difference does not meet the pressure difference threshold, adjusting the amount of nitrogen in the liquid ammonia buffer tank and / or the liquid ammonia storage tank includes: In a case where the pressure difference is greater than the upper pressure difference threshold, injecting the nitrogen in the nitrogen source into the liquid ammonia buffer tank according to the preset injection amount; When the pressure difference is less than the lower limit of the pressure difference threshold, the nitrogen in the nitrogen source is injected into the liquid ammonia storage tank according to the preset injection amount.

4. The method according to claim 1, wherein The reflux cooling module includes a reflux cooler; The method of using the reflux cooling module to process the ammonia gas overflowing from the high-pressure injection module to obtain recovered liquid ammonia includes: The reflux cooler is used to cool the ammonia gas at the third pressure overflowing from the high-pressure injection module to obtain recovered liquid ammonia at the third pressure.

5. The method according to claim 4, wherein the high-pressure injection module comprises a common rail and an injector; in, The high-pressure injection module injects the preset supply amount of liquid ammonia into the engine cylinder for combustion and work, including: Using the common rail pipe to perform pressure stabilization on the liquid ammonia output from the liquid ammonia buffer tank to obtain pressure-stabilized liquid ammonia; The common rail pipe transports the pressure-stabilized liquid ammonia to the injector; The injector injects the preset supply amount of liquid ammonia into the engine cylinder for combustion and work, and / or the ammonia gas overflows from the injector to be recovered and processed by the reflux cooling module.

6. The method according to any one of claims 1 to 5, wherein The liquid ammonia in the liquid ammonia buffer tank is pumped into the high-pressure injection module in the following manner: pressurizing the liquid ammonia output from the liquid ammonia buffer tank using the liquid ammonia boosting module to obtain liquid ammonia at a fourth pressure; The liquid ammonia at the fourth pressure is delivered to the high-pressure injection module.

7. The method according to claim 6, wherein the liquid ammonia boosting module comprises a compressor, a controller and a gas-liquid boosting pump; in, The step of pressurizing the liquid ammonia outputted from the liquid ammonia buffer tank by using the liquid ammonia boosting module to obtain liquid ammonia at a fourth pressure includes: Under the control of the controller, the compressor delivers compressed air to the gas-liquid booster pump; The compressed air is used to drive the gas-liquid booster pump to operate, so that the gas-liquid booster pump pressurizes the liquid ammonia output from the liquid ammonia buffer tank to obtain liquid ammonia at the fourth pressure.

8. An ammonia fuel supply system for high-pressure direct injection of liquid ammonia, comprising: Liquid ammonia storage module, including: a nitrogen source, wherein the nitrogen source stores nitrogen at a first pressure; a liquid ammonia storage tank, connected to the nitrogen source via a pipeline provided with a solenoid valve, wherein the liquid ammonia storage tank stores liquid ammonia at a second pressure; a liquid ammonia buffer tank, connected to the nitrogen source and the liquid ammonia storage tank through pipelines, wherein the gas pressure of the liquid ammonia buffer tank is the third gas pressure; Wherein, the liquid ammonia buffer tank is provided with a liquid level gauge, and the liquid level gauge is constructed as follows: Measuring the liquid level of the liquid ammonia in the liquid ammonia buffer tank; When the liquid level height does not meet the preset height range, controlling the working state of the solenoid valve to adjust the injection amount of nitrogen in the nitrogen source into the liquid ammonia storage tank, wherein the injection amount of the nitrogen can change the pressure difference between the liquid ammonia storage tank and the liquid ammonia buffer tank, thereby changing the speed at which the liquid ammonia in the liquid ammonia storage tank is injected into the liquid ammonia buffer tank; The liquid ammonia buffer tank is used to pressurize the liquid ammonia in the liquid ammonia buffer tank using the liquid ammonia booster module when the liquid level height is within the preset height range, and pump the pressurized liquid ammonia to the high-pressure injection module according to the preset supply amount; The high-pressure injection module is configured to inject the preset supply amount of liquid ammonia into the engine cylinder for combustion and work. The reflux cooling module is then used to treat the ammonia gas overflowing from the high-pressure injection module to obtain recovered liquid ammonia, which is then injected into the liquid ammonia buffer tank.

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