Combustion control system and method for ammonia-diesel dual-fuel engine

Abstract

The invention provides an ammonia diesel dual-fuel engine combustion control system and method, and relates to the technical field of engines. The control system comprises an engine, an ammonia supply device, a control device and a diesel supply device, a cylinder cover of the engine is provided with a diesel electric control nozzle, and an air inlet valve of the engine is communicated with the air inlet pipe. The ammonia supply device comprises an ammonia gas bottle, an ammonia pipeline and a gas ammonia nozzle, and the control device is used for adjusting the energy substitution rate of ammonia by controlling the ammonia fuel injection amount of the gas ammonia nozzle and the diesel oil injection amount of the diesel oil electronic control nozzle and controlling the diesel oil electronic control nozzle to adopt different injection modes under the condition of different ammonia energy substitution rates. The control strategy that the overall excess air coefficient is 1.0 is adopted to reduce emission of nitric oxide and particulate matter in tail gas, different injection modes are adopted according to different ammonia energy replacement rates, the optimal in-cylinder combustion effect is achieved under the different ammonia energy replacement rates, the power of the engine is improved, the emission amount of the nitric oxide and the particulate matter is reduced, and the energy consumption of the engine is reduced. And efficient and stable combustion of the engine is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of engines, and in particular to a combustion control system and method for an ammonia-diesel dual-fuel engine. Background Art

[0002] In recent years, countries around the world have paid increasing attention to the research and application of ammonia fuel. Due to the high natural temperature, large ignition energy, slow combustion speed and other limiting factors of ammonia fuel, it is difficult to use it as a single fuel in the engine. It is usually mixed with high-activity fuel in the engine to expand the applicable working conditions of ammonia fuel. A lot of research has been done on the mixed combustion of ammonia and diesel. At present, the supply of ammonia fuel for the application of ammonia-diesel dual fuel in the engine is divided into low-pressure gas ammonia injection in the intake duct and high-pressure liquid ammonia injection in the cylinder. If low-pressure gas ammonia injection is used, it belongs to premixed combustion. Ammonia and air are mixed more evenly, so that ammonia burns more fully. However, since gas ammonia occupies a part of the air volume in the intake duct, it will increase pumping loss when the ammonia energy substitution rate is high, which is not conducive to the efficient combustion of the engine; if high-pressure liquid ammonia injection is used in the cylinder, it belongs to diffusion combustion. The injection phase can be precisely controlled and does not occupy the air volume of the intake duct, which makes it easier to achieve a high substitution rate of ammonia combustion. However, due to the large latent heat of vaporization of liquid ammonia, the vaporization of liquid ammonia injected into the cylinder will cause the temperature in the cylinder to drop sharply, which is not conducive to flame propagation and combustion of the mixture in the cylinder.

[0003] On the other hand, when the overall excess air coefficient of a pure diesel engine is 1.0, the combustion is rough, the engine shakes greatly, the thermal efficiency is low, and the "black smoke" phenomenon occurs. Generally, a lean burn method is used to increase the oxygen content, which can reduce carbon soot and particulate matter emissions, but it cannot avoid the generation of carbon soot and particulate matter under high load. During the combustion of ammonia-diesel dual fuel, the zero carbon property of ammonia fuel will not increase carbon soot emissions, so the organization strategy of the mixture can be different from that of a diesel engine. In order to solve the above problems, it is necessary to provide a control method for an ammonia-diesel dual fuel engine. Summary of the invention

[0004] The present invention provides an ammonia-diesel dual-fuel engine combustion control system, which is used to solve the problems of low engine efficiency and high emission of nitrogen oxides and particulate matter in the prior art.

[0005] The present invention provides an ammonia-diesel dual-fuel engine combustion control system, comprising: An engine, wherein a cylinder head of the engine is provided with a diesel electronically controlled nozzle, an intake valve of the engine is connected to an intake pipe, and a high-pressure fuel rail pressure of the engine is greater than or equal to 1400 bar; an ammonia supply device, comprising an ammonia cylinder, an ammonia pipeline and an ammonia gas nozzle, wherein the diesel electronically controlled nozzle is connected to the outlet of the ammonia cylinder through the ammonia pipeline, the ammonia gas nozzle is arranged on the intake pipe, and the ammonia gas nozzle is used to spray ammonia gas into the intake pipe, and the spray pressure of the ammonia gas nozzle is greater than or equal to 5 bar and less than or equal to 7 bar; a control device, the control device being electrically connected to the gas ammonia nozzle and the diesel electronically controlled nozzle, the control device being used to adjust the energy substitution rate of ammonia by controlling the ammonia injection amount of the gas ammonia nozzle and the diesel injection amount of the diesel electronically controlled nozzle, and controlling the diesel electronically controlled nozzle to adopt different injection modes under different ammonia energy substitution rates; A diesel supply device is connected to the diesel electronically controlled nozzle, and is used to deliver diesel to the diesel electronically controlled nozzle.

[0006] According to an ammonia-diesel dual-fuel engine combustion control system provided by the present invention, the ammonia supply device further comprises: A first mass flow meter is provided in the ammonia pipeline, and is used to detect the flow rate and quality of ammonia outputted from the ammonia cylinder.

[0007] According to an ammonia-diesel dual-fuel engine combustion control system provided by the present invention, the ammonia supply device further comprises: A pressure reducing valve is arranged at the outlet of the ammonia cylinder, and is used to reduce the pressure of ammonia outputted from the outlet of the ammonia cylinder.

[0008] According to the present invention, an ammonia-diesel dual-fuel engine combustion control system further includes: A first display device, wherein the first display device is electrically connected to the first mass flow meter, and the first display device is used to display the flow rate and quality of ammonia outputted by the ammonia cylinder.

[0009] According to an ammonia-diesel dual-fuel engine combustion control system provided by the present invention, the intake pipe is provided with a pressure regulating valve and a pressure stabilizing tank, the pressure regulating valve is used to adjust the intake pressure of the intake pipe, the pressure regulating valve is electrically connected to the first display device and the control device, the first display device is also used to display the intake pressure of the intake pipe; the pressure stabilizing tank is used to maintain the pressure in the intake pipe stable, and the pressure stabilizing tank is electrically connected to the control device.

[0010] According to the present invention, an ammonia-diesel dual-fuel engine combustion control system further includes: An electric dynamometer, the output shaft of the engine is connected to the electric dynamometer.

[0011] According to an ammonia-diesel dual-fuel engine combustion control system provided by the present invention, the diesel supply device comprises an oil storage tank, an oil pipeline, a filter and a high-pressure oil pump, and the oil storage tank is connected to the diesel electronically controlled nozzle through the oil pipeline; The filter is arranged at the oil inlet of the oil pipeline, and the high-pressure oil pump is connected in series to the oil pipeline.

[0012] According to an ammonia-diesel dual-fuel engine combustion control system provided by the present invention, the cylinder head of the engine is also provided with a liquid ammonia nozzle and a glow plug, the liquid ammonia nozzle is connected to the outlet of the ammonia cylinder through a liquid ammonia pipeline, a boost pump and a second mass flow meter are provided on the liquid ammonia pipeline, the liquid ammonia nozzle and the glow plug are both electrically connected to the control device, and the second mass flow meter is electrically connected to the first display device.

[0013] According to an ammonia-diesel dual-fuel engine combustion control system provided by the present invention, during the operation of the engine, ammonia and diesel form an ammonia-diesel mixed gas inside the engine, and the overall excess air coefficient λ of the ammonia-diesel mixed gas can be calculated by the following formula (1); (1) in, is the theoretical air-fuel ratio of the ammonia-diesel mixture, It can be calculated by the following formula (2); (2) in, is the theoretical air-fuel ratio of pure diesel, is the theoretical air-fuel ratio of pure ammonia, is the mass flow rate of the ammonia fuel, is the flow rate of diesel; is the actual air-fuel ratio of the ammonia-diesel mixture. It can be calculated by the following formula (3); (3) If high-pressure liquid ammonia injection is used, It can be calculated by the following formula (4); (4) in, is the air flow rate in the intake pipe.

[0014] The present invention also provides an ammonia-diesel dual-fuel engine combustion control method, the control method is based on any of the above-mentioned ammonia-diesel dual-fuel engine combustion control systems, the engine adopts a control strategy with an overall excess air coefficient of 1.0, and the compression ratio of the engine is 18-23 to reduce the emission of nitrogen oxides and particulate matter in the exhaust gas, and the control method comprises: When the ammonia replacement rate is less than 30%, the diesel electronically controlled nozzle is controlled to perform pre-injection 10°-20°CA before the top dead center, and the diesel electronically controlled nozzle is controlled to perform main injection 2°-4°CA before the top dead center; When the ammonia replacement rate is between 30% and 70%, the diesel electronically controlled nozzle is controlled to perform pre-injection at 20° to 60° CA before the top dead center, the diesel electronically controlled nozzle is controlled to perform main injection at 2° to 4° CA before the top dead center, and the diesel electronically controlled nozzle is controlled to perform post-injection at 10° to 40° CA before the top dead center; When the ammonia replacement rate is between 70% and 100%, the diesel electronically controlled nozzle is controlled to perform main injection at 0° to 10° CA before the top dead center, and the liquid ammonia nozzle is controlled to perform liquid ammonia injection at 20° to 300° CA before the top dead center.

[0015] The ammonia-diesel dual-fuel engine combustion control system provided by the present invention adopts different injection methods according to different ammonia energy replacement rates, achieves the optimal in-cylinder combustion effect under different ammonia energy replacement rates, improves the engine power, reduces the amount of nitrogen oxides and particulate matter emissions, and realizes efficient and stable combustion of the engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a structural schematic diagram of the ammonia-diesel dual-fuel engine combustion control system provided by the present invention.

[0018] Figure 2 It is a schematic diagram of the IMEP of an engine with different overall excess air coefficients provided by the present invention.

[0019] Figure 3 It is a schematic diagram of nitrogen oxide emissions with different overall excess air coefficients provided by the present invention.

[0020] Figure 4 It is a schematic diagram of particulate matter emission when the overall excess air coefficient provided by the present invention is 1.0.

[0021] Figure 5 It is a structural schematic diagram of an ammonia-diesel dual-fuel engine combustion control system provided by another embodiment of the present invention.

[0022] Reference numerals: 10. Engine; 11. Diesel electronically controlled nozzle; 12. Intake pipe; 13. Pressure regulating valve; 14. Pressure regulating tank; 15. Liquid ammonia nozzle; 16. Glow plug; 17. Liquid ammonia pipeline; 18. Booster pump; 19. Second mass flow meter; 20. Ammonia supply device; 21. Ammonia cylinder; 22. Ammonia pipeline; 23. Ammonia nozzle; 24. First mass flow meter; 30. Control device; 40. Diesel supply device; 41. Oil storage tank; 42. Oil pipeline; 50. First display device; 60. Electric dynamometer; 70. Combustion analyzer; 71. Emission analyzer; 72. Engine particle analyzer; 73. Second display device. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limitations on the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0025] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0026] In the embodiments of the present invention, unless otherwise clearly specified and limited, the first feature being "above" or "below" the second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0027] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0028] Combine the following Figure 1-Figure 5 The specific structure and working principle of the ammonia-diesel dual-fuel engine combustion control system of the present invention are described.

[0029] Figure 1 The structural schematic diagram of the ammonia-diesel dual-fuel engine combustion control system provided by the present invention is illustrated as follows: Figure 1As shown, the combustion control system of the ammonia-diesel dual-fuel engine includes an engine 10, an ammonia supply device 20, a control device 30 and a diesel supply device 40. The cylinder head of the engine 10 is provided with a diesel electronically controlled nozzle 11. The intake valve of the engine 10 is connected to the intake pipe 12. The pressure of the high-pressure rail of the engine 10 is greater than or equal to 1400 bar. The ammonia supply device 20 includes an ammonia cylinder 21, an ammonia pipeline 22 and an ammonia gas nozzle 23. The diesel electronically controlled nozzle 11 is connected to the outlet of the ammonia cylinder 21 through the ammonia pipeline 22. The ammonia gas nozzle 23 is provided in the intake pipe 12. The ammonia gas nozzle 23 is used to spray ammonia into the intake pipe 12. The injection pressure of the ammonia gas nozzle 23 is greater than or equal to 5 bar and less than or equal to 7 bar. The control device 30 is electrically connected to the gas ammonia nozzle 23 and the diesel electronically controlled nozzle 11. The control device 30 is used to adjust the energy substitution rate of ammonia by controlling the ammonia injection amount of the gas ammonia nozzle 23 and the diesel injection amount of the diesel electronically controlled nozzle 11, and control the diesel electronically controlled nozzle 11 to adopt different injection methods under different ammonia energy substitution rates. The diesel supply device 40 is connected to the diesel electronically controlled nozzle 11, and the diesel supply device 40 is used to deliver diesel to the diesel electronically controlled nozzle 11.

[0030] The ammonia-diesel dual-fuel engine combustion control system provided by the present invention adopts different injection methods according to different ammonia energy replacement rates, achieves the optimal in-cylinder combustion effect under different ammonia energy replacement rates, improves the power of the engine 10, reduces the amount of nitrogen oxides and particulate matter emissions, and realizes efficient and stable combustion of the engine 10.

[0031] In one embodiment of the present invention, the control device 30 is an ECU control unit. Of course, the specific type of the control device 30 is not limited thereto, and other types of control devices 30 may also be used.

[0032] The gas ammonia nozzle 23 sprays ammonia into the intake pipe 12, and the injection pressure is not less than 5 bar and less than or equal to 7 bar. Diesel is injected into the cylinder of the engine 10 through the diesel electronically controlled nozzle 11 by direct injection, wherein the high-pressure rail pressure should be not less than 1400 bar to obtain a long penetration distance. According to the intake volume and the ammonia energy ratio, the control device 30 controls the ammonia injection amount of the gas ammonia nozzle 23 and the diesel injection amount of the diesel electronically controlled nozzle 11. According to the intake volume and power requirements of the engine 10, the overall excess air coefficient of the ammonia-diesel dual fuel is always maintained at 1.0, and the corresponding injection strategy is adopted under different engine 10 operating conditions to achieve the optimal in-cylinder combustion effect, and realize efficient, clean and stable combustion of the engine 10.

[0033] In one embodiment of the present invention, the ammonia supply device 20 further includes a first mass flow meter 24, which is disposed in the ammonia pipeline 22 and is used to detect the flow rate and quality of ammonia outputted from the ammonia cylinder 21. The control device 30, the first mass flow meter 24 and the ammonia nozzle 23 cooperate to realize closed-loop control, thereby accurately controlling the ammonia injection amount.

[0034] In one embodiment of the present invention, the ammonia supply device 20 further includes a pressure reducing valve, which is disposed at the outlet of the ammonia cylinder 21 and is used to reduce the ammonia pressure output from the outlet of the ammonia cylinder 21 to meet the combustion requirements of the engine 10. Since the storage of ammonia is based on liquid storage, the natural gasification speed of liquid ammonia is slow, and the pressure reducing valve plays a key role in this process, increasing the gasification speed of ammonia and solving the fuel supply problem of the ammonia-diesel engine 10.

[0035] In one embodiment of the present invention, the ammonia-diesel dual-fuel engine combustion control system further includes a first display device 50, which is electrically connected to the first mass flow meter 24, and is used to display the flow rate and quality of ammonia outputted by the ammonia cylinder 21. The first mass flow meter 24 is a high-precision measuring device that can measure the flow quality and volume flow of ammonia. The first display device 50 displays the flow rate and quality of ammonia outputted by the ammonia cylinder 21 in real time, which is essential for monitoring the combustion efficiency of the engine 10 and ensuring the safe operation of the engine 10. The control device 30 can adjust the fuel supply, optimize the combustion process, and improve the combustion efficiency of the engine 10 through these data.

[0036] In one embodiment of the present invention, the intake pipe 12 is provided with a pressure regulating valve 13 and a pressure stabilizing tank 14. The pressure regulating valve 13 is used to adjust the intake pressure of the intake pipe 12. The pressure regulating valve 13 is electrically connected to the first display device 50 and the control device 30. The first display device 50 is also used to display the intake pressure of the intake pipe 12. The control device 30 can accurately control the intake amount of the intake pipe 12 by controlling the pressure regulating valve 13. The pressure stabilizing tank 14 is used to maintain the pressure in the intake pipe 12 stable. The pressure stabilizing tank 14 is electrically connected to the control device 30. The pressure regulating valve 13 and the pressure stabilizing tank 14 work together. The pressure regulating valve 13 is responsible for adjusting the pressure as needed, while the pressure stabilizing tank 14 is responsible for providing a buffer when the pressure fluctuates to maintain the pressure in the intake pipe 12 stable.

[0037] In one embodiment of the present invention, the combustion control system of the ammonia-diesel dual-fuel engine further includes an electric dynamometer 60, the output shaft of the engine 10 is connected to the electric dynamometer 60, and the electric dynamometer 60 is electrically connected to the control device 30. The electric dynamometer 60 measures the mechanical energy output by the engine 10 and converts it into electrical energy for measurement. This energy conversion process enables the electric dynamometer 60 to accurately measure the power output of the engine 10. The electric dynamometer 60 optimizes combustion efficiency and reduces emissions by testing and evaluating the performance of the engine 10.

[0038] In one embodiment of the present invention, the diesel supply device 40 includes an oil storage tank 41 and an oil delivery pipe 42 , and the oil storage tank 41 is connected to the diesel electronically controlled nozzle 11 through the oil delivery pipe 42 .

[0039] In one embodiment of the present invention, the diesel supply device 40 also includes a filter and a high-pressure oil pump. The filter is arranged at the oil inlet of the oil delivery pipe 42, and its main function is to filter impurities and water in the fuel. This is essential for protecting precision parts such as the injection pump and the injector from wear and blockage. The high-pressure oil pump is connected in series to the oil delivery pipe 42. The function of the high-pressure oil pump is to pressurize the low-pressure fuel that has been preliminarily filtered to a certain pressure, and to deliver the diesel to the diesel electronically controlled nozzle 11 at a certain pressure, flow rate and cleanliness. This is essential for the stable combustion and performance of the ammonia-diesel dual-fuel engine 10, because the injection of diesel must be precisely synchronized with the injection of ammonia to achieve optimal combustion efficiency and minimum emissions.

[0040] In one embodiment of the present invention, Figure 5 The structural diagram of the combustion control system of an ammonia-diesel dual-fuel engine provided by another embodiment of the present invention is illustrated as follows Figure 5As shown, the cylinder head of the engine 10 is further provided with a liquid ammonia nozzle 15 and a glow plug 16. The liquid ammonia nozzle 15 is connected to the outlet of the ammonia cylinder 21 through a liquid ammonia pipeline 17. A booster pump 18 and a second mass flow meter 19 are provided on the liquid ammonia pipeline 17. The liquid ammonia nozzle 15 and the glow plug 16 are both electrically connected to the control device 30, and the second mass flow meter 19 is electrically connected to the first display device 50. The second mass flow meter 19 is used to detect the flow and mass of the liquid ammonia output from the ammonia cylinder 21, the liquid ammonia nozzle 15 is used to spray liquid ammonia onto the surface of the glow plug 16, and the glow plug 16 is used to heat the liquid ammonia. At a high replacement rate of 70% to 100%, the combustion of ammonia will dominate. If the intake pipe gas supply method is adopted, it will occupy the air volume of the intake pipe, increase the pump air loss, and is not conducive to the improvement of the engine thermal efficiency. Therefore, the liquid ammonia supply method is adopted, through the liquid ammonia pipeline 17 and the boost pump 18, and then directly injected into the cylinder through the liquid ammonia nozzle 15, the injection pressure is 200~1000bar. The injection time is adjusted at 20°CA~300°CA before the top dead center. Due to the large latent heat of vaporization of ammonia, the temperature in the cylinder will drop sharply when liquid ammonia enters the cylinder. Therefore, the electric glow plug 16 is added for heating, so that the liquid ammonia is sprayed on the electric glow plug 16 to make up for the heat absorbed by the vaporization of liquid ammonia, increase the temperature in the cylinder, promote the full combustion of ammonia fuel, and reduce the emission of unburned ammonia. In order to improve the combustion efficiency of ammonia fuel, the compression ratio of the engine must be a high compression ratio of 18~23.

[0041] In one embodiment of the present invention, the diesel supply device 40 also includes a combustion analyzer 70, an emission analyzer 71, an engine particle analyzer DMS500 and a second display device 73, where the engine particle analyzer DMS500 is referred to as the engine particle analyzer 72. The exhaust valve of the engine 10 is connected to the exhaust pipe, and the combustion analyzer 70, the emission analyzer 71 and the engine particle analyzer 72 are all connected to the exhaust pipe. The combustion analyzer 70, the emission analyzer 71 and the engine particle analyzer 72 are all electrically connected to the second display device 73. The combustion analyzer 70 is used to measure and analyze various parameters in the combustion process of the engine 10, such as combustion efficiency, combustion stability and combustion temperature. These parameters are very important for optimizing the combustion process of the engine 10, improving combustion efficiency and reducing emissions. By accurately controlling the combustion process, the generation of harmful emissions can be reduced and the utilization rate of fuel can be improved. The emission analyzer 71 is used to measure and analyze the gas components emitted by the engine 10, including but not limited to carbon dioxide, carbon monoxide, nitrogen oxides, hydrocarbons, etc. These data are very important for evaluating the environmental performance of the engine 10 and complying with emission standards. The emission analyzer 71 can help engineers understand the composition of the emissions and take appropriate measures to reduce the emission of pollutants. The engine particle analyzer 72 is used to measure the particulate matter in the emissions of the engine 10. The engine particle analyzer 72 can measure particles ranging in size from 5 nanometers to 2.5 microns and provide real-time particle size, quantity and mass data.

[0042] In one embodiment of the present invention, during the operation of the engine 10, ammonia and diesel form an ammonia-diesel mixture inside the engine 10, and the overall excess air coefficient λ of the ammonia-diesel mixture can be calculated by the following formula (1): (1) in, is the theoretical air-fuel ratio of the ammonia-diesel mixture, It can be calculated by the following formula (2); (2) in, is the theoretical air-fuel ratio of pure diesel, The value of is 14.5; is the theoretical air-fuel ratio of pure ammonia, The value of is 6.17; is the mass flow rate of ammonia fuel, is the flow rate of diesel; is the actual air-fuel ratio of the ammonia-diesel mixture. It can be calculated by the following formula (3); (3) If high-pressure liquid ammonia injection is used, It can be calculated by the following formula (4); (4) in, is the air flow rate in the intake pipe.

[0043] When using formula (3) to calculate the actual air-fuel ratio, since ammonia is injected into the intake pipe, it will occupy a part of the air mass flow. Therefore, in the calculation of the actual air-fuel ratio, the mass of ammonia in the intake pipe needs to be subtracted.

[0044] The ammonia-diesel dual-fuel engine combustion control system provided by the present invention adopts different injection methods according to different ammonia energy replacement rates, achieves the optimal in-cylinder combustion effect under different ammonia energy replacement rates, improves the power of the engine 10, reduces the amount of nitrogen oxides and particulate matter emissions, and realizes efficient and stable combustion of the engine 10.

[0045] The present invention also provides an ammonia-diesel dual-fuel engine combustion control method, the control method is based on the ammonia-diesel dual-fuel engine combustion control system described in any one of the above embodiments, the engine adopts a control strategy with an overall excess air coefficient of 1.0, and the compression ratio of the engine is 18-23 to reduce nitrogen oxides and particulate matter emissions in the exhaust gas. The ammonia-diesel dual-fuel engine combustion control method includes: When the ammonia replacement rate is less than 30%, the diesel electronically controlled nozzle 11 is controlled to perform pre-injection 10°-20°CA before the top dead center, and the diesel electronically controlled nozzle 11 is controlled to perform main injection 2°-4°CA before the top dead center; It should be noted here that when the ammonia replacement rate is less than 30%, the diesel combustion accounts for a large proportion, and the diesel electronically controlled nozzle 11 is controlled to perform a pre-injection 10°-20°CA before the compression top dead center. The heat released by the combustion of this part of the diesel increases the overall temperature in the engine cylinder, so that the diesel entering the cylinder during the main injection (2°-4°CA before the top dead center) can ignite faster, reduce the proportion of diesel premixed combustion, reduce the maximum pressure rise rate, and avoid rough combustion.

[0046] When the ammonia replacement rate is between 30% and 70%, the diesel electronically controlled nozzle 11 is controlled to perform pre-injection at 20°-60°CA before the top dead center, the diesel electronically controlled nozzle 11 is controlled to perform main injection at 2°-4°CA before the top dead center, and the diesel electronically controlled nozzle 11 is controlled to perform post-injection at 10°-40°CA before the top dead center; It should be noted here that when the ammonia replacement rate is between 30% and 70%, the pre-injection timing can be further advanced to 20°-60°CA before top dead center. By advancing the hot atmosphere of the mixture in the cylinder at the time of pre-injection, the ammonia combustion efficiency is improved. At the same time, an additional post-injection (10-40°CA after top dead center) is added to ignite the unburned ammonia near the cylinder wall and reduce the emission of unburned ammonia. The timing of the post-injection should not be too late to reduce the impact on the thermal efficiency of the engine 10.

[0047] When the ammonia replacement rate is between 70% and 100%, the diesel electronically controlled nozzle 11 is controlled to perform main injection at 0°-10° CA before the top dead center, and the liquid ammonia nozzle 15 is controlled to perform liquid ammonia injection at 20°-300° CA before the top dead center.

[0048] When the ammonia replacement rate is higher than 70%, the diesel injection volume is reduced and the rough combustion phenomenon is weakened, so no diesel pre-injection is performed to improve the combustion isochoricity, reduce excessive heat transfer losses, and thus improve combustion efficiency. At this time, the main injection is performed in a low temperature environment and has a longer ignition delay period, so the main injection timing needs to be appropriately relaxed to 0-10 °CA before compression top dead center.

[0049] Figure 2 The schematic diagram of the engine IMEP with different overall excess air coefficients provided by the present invention is illustrated. Figure 3 The schematic diagram of nitrogen oxide emission with different overall excess air coefficients provided by the present invention is illustrated. Figure 4 The schematic diagram of particulate matter emission when the overall excess air coefficient provided by the present invention is 1.0 is illustrated as follows: Figures 2 to 4 As shown, the combustion control method of the ammonia-diesel dual-fuel engine of the present invention controls the diesel injection amount according to the intake amount and the ammonia replacement rate, so that the overall excess air coefficient is controlled to 1.0. The control strategy of using the overall excess air coefficient of 1.0 can effectively reduce the emission of nitrogen oxides and particulate matter in the exhaust gas through combustion means, while improving the IMEP (Indicated mean effective pressure) of the engine 10.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An ammonia-diesel dual-fuel engine combustion control system, characterized in that: include: An engine (10), wherein a cylinder head of the engine (10) is provided with a diesel electronically controlled nozzle (11), an intake valve of the engine (10) is in communication with an intake pipe (12), and a high-pressure fuel rail pressure of the engine (10) is greater than or equal to 1400 bar; An ammonia supply device (20) comprises an ammonia cylinder (21), an ammonia pipeline (22) and an ammonia gas nozzle (23), wherein the diesel electronically controlled nozzle (11) is connected to the outlet of the ammonia cylinder (21) via the ammonia pipeline (22), the ammonia gas nozzle (23) is arranged on the air intake pipe (12), and the ammonia gas nozzle (23) is used to spray ammonia gas into the air intake pipe (12), and the spray pressure of the ammonia gas nozzle (23) is greater than or equal to 5 bar and less than or equal to 7 bar; a control device (30), the control device (30) being electrically connected to the gas ammonia nozzle (23) and the diesel electronically controlled nozzle (11), the control device (30) being used to adjust the energy replacement rate of ammonia by controlling the ammonia injection amount of the gas ammonia nozzle (23) and the diesel injection amount of the diesel electronically controlled nozzle (11), and controlling the diesel electronically controlled nozzle (11) to adopt different injection modes under different ammonia energy replacement rate conditions; A diesel supply device (40), the diesel supply device (40) being in communication with the diesel electronically controlled nozzle (11), the diesel supply device (40) being used to deliver diesel to the diesel electronically controlled nozzle (11).

2. The combustion control system of the ammonia-diesel dual-fuel engine according to claim 1, characterized in that: The ammonia supply device (20) further comprises: A first mass flow meter (24), the first mass flow meter (24) being arranged on the ammonia pipeline (22), the first mass flow meter (24) being used to detect the flow rate and quality of ammonia gas outputted from the ammonia gas bottle (21).

3. The combustion control system of the ammonia-diesel dual-fuel engine according to claim 2, characterized in that: The ammonia supply device (20) further comprises: A pressure reducing valve, the pressure reducing valve being arranged at the outlet of the ammonia cylinder (21), the pressure reducing valve being used to reduce the pressure of ammonia outputted from the outlet of the ammonia cylinder (21).

4. The combustion control system of the ammonia-diesel dual-fuel engine according to claim 2, characterized in that: Also includes: A first display device (50), the first display device (50) is electrically connected to the first mass flow meter (24), and the first display device (50) is used to display the flow rate and mass of ammonia outputted by the ammonia cylinder (21).

5. The combustion control system of the ammonia-diesel dual-fuel engine according to claim 4, characterized in that: The air intake pipe (12) is provided with a pressure regulating valve (13) and a pressure stabilizing tank (14); the pressure regulating valve (13) is used to regulate the air intake pressure of the air intake pipe (12); the pressure regulating valve (13) is electrically connected to the first display device (50) and the control device (30); the first display device (50) is also used to display the air intake pressure of the air intake pipe (12); the pressure stabilizing tank (14) is used to maintain the pressure in the air intake pipe (12) stable; the pressure stabilizing tank (14) is electrically connected to the control device (30).

6. The combustion control system of an ammonia-diesel dual-fuel engine according to any one of claims 1 to 5, characterized in that: Also includes: An electric dynamometer (60), to which the output shaft of the engine (10) is connected.

7. The combustion control system of an ammonia-diesel dual-fuel engine according to any one of claims 1 to 5, characterized in that: The diesel supply device (40) comprises an oil storage tank (41), an oil delivery pipe (42), a filter and a high-pressure oil pump; the oil storage tank (41) is connected to the diesel electronically controlled nozzle (11) via the oil delivery pipe (42); the filter is arranged at the oil inlet of the oil delivery pipe (42), and the high-pressure oil pump is connected in series to the oil delivery pipe (42).

8. The combustion control system of an ammonia-diesel dual-fuel engine according to claim 4 or 5, characterized in that: The cylinder head of the engine (10) is further provided with a liquid ammonia nozzle (15) and a glow plug (16); the liquid ammonia nozzle (15) is connected to the outlet of the ammonia cylinder (21) via a liquid ammonia pipeline (17); a booster pump (18) and a second mass flow meter (19) are provided on the liquid ammonia pipeline (17); the liquid ammonia nozzle (15) and the glow plug (16) are both electrically connected to the control device (30); and the second mass flow meter (19) is electrically connected to the first display device (50).

9. The combustion control system of an ammonia-diesel dual-fuel engine according to any one of claims 1 to 5, characterized in that: During the operation of the engine (10), ammonia and diesel form an ammonia-diesel mixed gas inside the engine (10), and the overall excess air coefficient λ of the ammonia-diesel mixed gas can be calculated by the following formula (1); （1） in, is the theoretical air-fuel ratio of the ammonia-diesel mixture, It can be calculated by the following formula (2); （2） in, is the theoretical air-fuel ratio of pure diesel, is the theoretical air-fuel ratio of pure ammonia, is the mass flow rate of ammonia in the intake pipe, is the flow rate of diesel; is the actual air-fuel ratio of the ammonia-diesel mixture. It can be calculated by the following formula (3); （3） If high-pressure liquid ammonia injection is used, It can be calculated by the following formula (4); （4） in, is the air flow rate in the intake pipe.

10. A combustion control method for an ammonia-diesel dual-fuel engine, the control method being based on the combustion control system for an ammonia-diesel dual-fuel engine according to any one of claims 1 to 9, characterized in that: The engine adopts a control strategy with an overall excess air coefficient of 1.0, and the compression ratio of the engine is 18-23 to reduce the emission of nitrogen oxides and particulate matter in the exhaust gas. The control method includes: When the ammonia replacement rate is less than 30%, the diesel electronically controlled nozzle (11) is controlled to perform pre-injection 10°-20°CA before the top dead center, and the diesel electronically controlled nozzle (11) is controlled to perform main injection 2°-4°CA before the top dead center; When the ammonia replacement rate is between 30% and 70%, the diesel electronically controlled nozzle (11) is controlled to perform pre-injection at 20° to 60° CA before the top dead center, the diesel electronically controlled nozzle (11) is controlled to perform main injection at 2° to 4° CA before the top dead center, and the diesel electronically controlled nozzle (11) is controlled to perform post-injection at 10° to 40° CA before the top dead center; When the ammonia replacement rate is between 70% and 100%, the diesel electronically controlled nozzle (11) is controlled to perform main injection at 0° to 10° CA before the top dead center, and the liquid ammonia nozzle (15) is controlled to perform liquid ammonia injection at 20° to 300° CA before the top dead center.

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