A diesel-ammonia dual-fuel engine combustion system and combustion method based on high-low temperature EGR active reforming

Abstract

The application aims to provide a diesel / ammonia dual-fuel engine combustion system and combustion method based on high and low temperature EGR activity reforming, which comprises a common rail dual-injector system, an ammonia fuel injector, a high and low temperature EGR system and the like, in order to realize engine fuel injection precision control, the ammonia fuel is supplied by using an intake port multi-point injection mode, and the diesel fuel is supplied by using a common rail dual-injector high and low flow injection mode. According to the diesel / ammonia dual-fuel engine operating condition, two working modes of pure diesel combustion mode and dual-fuel combustion mode are adopted, and a Miller cycle is used to optimize the engine thermal efficiency, and high and low temperature EGR is used to adjust the fuel combustion activity, so as to improve the engine efficiency and reduce the pollutant emission under the full operating condition of the engine.

Description

TECHNICAL FIELD

[0001] The present application relates to an engine combustion system, in particular a dual-fuel engine combustion system and method. BACKGROUND

[0002] Ammonia, as a nitrogen hydrogen compound, has no carbon emissions in the combustion process, and is currently the largest chemical product in addition to sulfuric acid, with a wide range of sources and low cost. However, ammonia fuel engines are not widely used at present because there are technical problems to be solved, including: ammonia fuel has a high ignition point, a high minimum ignition energy, is prone to generate nitrogen oxide pollutants, and has problems such as insufficient ammonia fuel combustion under low load conditions and increased nitrogen oxide generation under high temperature conditions in the cylinder under high load conditions during the combustion process. SUMMARY

[0003] The purpose of the present application is to provide a diesel / ammonia dual-fuel engine combustion system and combustion method based on high / low temperature EGR active reforming, which can fully utilize the advantages of ammonia fuel, such as low pollution, high octane value, and high economic efficiency, and can balance emissions, power, and economy.

[0004] The purpose of the present application is achieved as follows:

[0005] The diesel / ammonia dual-fuel engine combustion system based on high / low temperature EGR active reforming according to the present application is characterized by comprising a cylinder wall, a cylinder head, a piston, a diesel tank, an ammonia fuel storage tank, and a high / low temperature EGR system. The cylinder wall, the cylinder head, and the piston form a cylinder. The cylinder head is provided with an oil injector a, an oil injector b, an intake valve, and an exhaust valve. The cylinder is connected to an intake manifold through the intake valve and connected to an exhaust manifold through the exhaust valve. The intake manifold is connected to an intake main pipe, and the exhaust manifold is connected to an exhaust main pipe. The diesel tank is sequentially connected to a fuel pump, a fuel filter, a fuel injector pump, and a high-pressure fuel rail. The high-pressure fuel rail is connected to the oil injector a and the oil injector b. The ammonia fuel storage tank is sequentially connected to an ammonia fuel delivery pump, an ammonia fuel filter, an ammonia fuel injector pump, and an ammonia fuel rail. The ammonia fuel rail is connected to an ammonia fuel injector. The high / low temperature EGR system comprises an EGR pipeline system. The two ends of the EGR pipeline system are connected to the intake main pipe and the exhaust main pipe, respectively. An EGR cooler and an EGR flow regulating valve are arranged on the EGR pipeline system. An air flow meter is installed on the intake main pipe before the EGR pipeline system. A back pressure regulating valve is installed on the exhaust main pipe after the EGR pipeline system.

[0006] The diesel / ammonia dual-fuel engine combustion system based on high / low temperature EGR active reforming according to the present application can further comprise:

[0007] 1. The oil injector a is vertically installed on the cylinder head, and the axis is coincident with the center line of the cylinder; the oil injector b is vertically installed on the cylinder head, and the axis is parallel to the axis of the oil injector a; the ammonia fuel injector is obliquely installed on the intake manifold, and the ammonia fuel injection direction is along the intake manifold to the inside of the cylinder.

[0008] 2. The oil injector a and the oil injector b adopt high-low flow step design, and the maximum flow of the oil injector a is much larger than that of the oil injector b; the nozzle of the oil injector a is single-hole design, and the oil injector b is multi-hole uneven design.

[0009] 3. The ammonia fuel injector is a single-hole injector structure with middle heating and shaft needle, and the heating resistor is installed in the middle of the ammonia fuel injector.

[0010] 4. The opening angle range of the back pressure regulating valve is 0-60°CA, when the opening angle is 0°CA, the back pressure regulating valve is in the fully open state, and when the opening angle is 90°CA, the back pressure regulating valve is in the fully closed state; the relationship between the opening angle of the back pressure regulating valve and the engine output power ratio X is [60*(0.5-X) R ]°CA.

[0011] 5. The opening angle range of the EGR flow regulating valve is 0-90°CA, when the opening angle is 0°CA, the EGR flow regulating valve 28 is in the fully closed state, and when the opening angle is 90°CA, the EGR flow regulating valve is in the fully open state; the relationship between the opening angle of the EGR flow regulating valve and the engine output power ratio X is [90*X Z ]°CA.

[0012] The combustion method of the diesel / ammonia dual-fuel engine based on high-low temperature EGR active reforming has the characteristics that: a pure diesel combustion mode is adopted, only low temperature EGR is used, the opening angle of the EGR flow regulating valve is [90*X Z ]°CA, when the diesel / ammonia dual-fuel engine is in the starting, idling and low load working conditions, the oil injector b is in the working state, the injection start point of the oil injector b is before the compression top dead center, and is delayed with the increase of the load; when the engine is in the medium and high load working conditions, the oil injector a and the oil injector b work simultaneously, and the oil injector a works in the linear characteristic area, the oil injector a starts to inject before the compression top dead center, and the injection start point is delayed with the increase of the load, and the oil injector b injects diesel when the engine output power is greater than 75% of the rated power, so that the power demand of the diesel / ammonia dual-fuel engine is met.

[0013] The combustion method of the diesel / ammonia dual-fuel engine based on high-low temperature EGR active reforming can further include:

[0014] 1. Including dual-fuel combustion mode: diesel / ammonia dual-fuel engine is in medium-high load operation stage, and high-low temperature EGR is used to adjust the fuel activity state in the cylinder, the opening angle of the back pressure regulating valve is [60*(1-X R )]℃A, the opening angle of the EGR flow regulating valve is [90*X Z ]℃A, when the load is low, the exhaust back pressure is increased by adjusting the back pressure regulating valve, the high-temperature exhaust gas retention rate in the cylinder is increased, the initial temperature of ammonia fuel combustion in the cylinder is increased, as the load increases, the opening angle of the back pressure regulating valve is reduced, the opening angle of the EGR flow regulating valve is increased, the proportion of low-temperature exhaust gas in the cylinder is increased, the number of inert gas molecules in the cylinder is increased, the ammonia fuel injector and the oil injector b work together, the ammonia fuel injector injection starting point is between 10℃A-40℃A after the exhaust valve is closed, and is advanced as the engine load increases, the injection end point is between 10℃A-20℃A before the intake valve is closed, the total heat value of the injected ammonia fuel accounts for 80%-85% of the total fuel heat value; the oil injector b sprays in the latter half of the compression stroke before the top dead center of compression, the heat value of the injected diesel fuel accounts for 15%-20% of the total fuel heat value, the ammonia fuel is mixed with air in the intake manifold and enters the cylinder, the high-low temperature EGR adjustment strategy is used, the combustible area is formed in the cylinder by injecting diesel, and the in-cylinder uniform combustion is accelerated.

[0015] The advantages of the present application are that: according to the operation condition of the diesel / ammonia dual-fuel engine, two working modes of pure diesel combustion mode and dual-fuel combustion mode are adopted, the engine thermal efficiency is optimized by combining with the Miller cycle, and the fuel combustion activity is adjusted by high-low temperature EGR, the advantages of low-carbon and multi-fuel complementation and synergy of the diesel / ammonia dual-fuel engine are fully utilized, multiple oil injectors are used to work together, the fuel injection precision control of the engine is improved, the emission of nitrogen oxides and pollutants of the engine is reduced, so that the diesel / ammonia dual-fuel engine can consider emission, power and economy under different conditions, realize high-efficiency and clean combustion of ammonia diesel dual-fuel engine, and fully utilize the advantages of ammonia fuel, such as low pollution, high octane value, economy and the like. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the present application;

[0017] Figure 2 It is a high-low temperature EGR system schematic diagram;

[0018] Figure 3 It is an ammonia fuel injector structure schematic diagram;

[0019] Figure 4 It is a cylinder fuel distribution diagram under low load condition in pure diesel combustion mode;

[0020] Figure 5In-cylinder fuel distribution map for medium and high load working condition under pure diesel combustion mode;

[0021] Figure 6 In-cylinder fuel distribution map for engine intake process under dual fuel combustion mode;

[0022] Figure 7 In-cylinder fuel distribution map for medium and high load working condition under dual fuel combustion mode;

[0023] Figure 8 Schematic diagram of fuel injector working phase range under pure diesel combustion mode;

[0024] Figure 9 Schematic diagram of fuel injector working phase range under dual fuel combustion mode;

[0025] Figure 10 Fuel injector working state and valve opening angle under pure diesel combustion mode;

[0026] Figure 11 Fuel injector working state and valve opening angle under dual fuel combustion mode. DETAILED DESCRIPTION

[0027] The application will be described in more detail below with examples and with reference to the accompanying drawings:

[0028] In combination with Figures 1-11 , the application comprises an ammonia fuel injector 7, an oil injector a11, an oil injector b12, a high-pressure oil rail 5, a back pressure regulating valve 22, an EGR cooler 29, an EGR pipeline system 30, an EGR flow regulating valve 28, an intake valve 10, a cylinder head 9, an exhaust valve 13, etc. The oil injector a11 is installed on the cylinder head 9, and its axis coincides with the center line of the cylinder. The oil injector b12 is installed vertically on the cylinder head 9, and its axis is parallel to the axis of the oil injector a11 and keeps a certain distance. The ammonia fuel injector 7 is installed obliquely on the intake manifold 8, and the ammonia fuel injection direction points to the inside of the cylinder along the intake manifold 8. The back pressure regulating valve 22 is installed on the exhaust manifold 23. The combustion method is as follows: according to the working condition of the diesel / ammonia dual fuel engine, two working modes of pure diesel combustion mode and dual fuel combustion mode are adopted, and the Miller cycle is used to optimize the thermal efficiency of the engine and the high and low temperature EGR is used to adjust the activity of in-cylinder fuel combustion. By optimizing the fuel injection amount, injection timing and injection law of the ammonia fuel injector 7, the oil injector a11 and the oil injector b12, the fuel injection precision of the engine is improved, the control of the in-cylinder fuel concentration distribution is realized, the advantages of low carbon and multi-fuel complementation and synergy of the diesel / ammonia dual fuel engine are fully developed, and the economy and power of the engine under the whole working condition are improved.

[0029] The high and low temperature EGR system comprises a back pressure regulating valve 22, an EGR cooler 29, an EGR pipeline system 30, an EGR flow regulating valve 28 and the like; the high and low temperature EGR system can realize high temperature EGR control and low temperature EGR control, the high temperature EGR works in a dual fuel working mode, the back pressure regulating valve 22 is adjusted to change the high temperature exhaust gas retention rate in the cylinder, the initial temperature of fuel combustion in the cylinder is adjusted, and thus the fuel combustion activity in the cylinder is affected; the low temperature EGR adjusts the EGR flow regulating valve 28 to adjust the proportion of low temperature exhaust gas and fresh air in the intake process, so as to adjust the inert gas concentration in the cylinder, reduce the highest temperature and pressure of combustion, and reduce the emission of nitrogen oxides in the emission.

[0030] The common rail dual injector system is composed of a high pressure oil rail 5, an injector a 11, an injector b 12 and the like; the injector a 11 and the injector b 12 are connected with the high pressure oil rail; the injector a 11 and the injector b 12 adopt high and low flow step design, and the maximum flow of the injector a 11 is much larger than that of the injector b 12; the injector a 11 nozzle is designed as a single injection hole, and the injector b 12 is designed as a multi-injection hole non-uniform design; the diesel injection amount of the injector a 11 can meet the fuel supply demand of the engine under high load and high speed; the diesel of the injector b 12 is uniformly distributed in the cylinder, and the injection amount meets the fuel supply accurate control under the engine low load and low speed working condition, starting condition, idling condition, ammonia fuel active reforming and pilot working condition.

[0031] The Miller cycle is used to improve the economy of the dual fuel engine, and long expansion stroke and short compression stroke design is adopted, that is, the opening period of the intake valve 10 is shortened in the intake process, and the intake valve is closed before the piston runs to the bottom dead center, so that the compression ratio of the cylinder is less than the expansion ratio, and the thermal efficiency of the engine is improved.

[0032] The ammonia fuel injector 7 has a middle section heating and a needle type single hole injector structure, a heating resistor 31 is installed in the middle section of the ammonia fuel injector 7, which works in the ammonia fuel injection stage, promotes ammonia fuel vaporization, and strengthens the disturbance between ammonia fuel and air in the intake stage to make the mixture uniform.

[0033] The combustion method is to change the proportion distribution, concentration and combustion mode of the fuel in the combustion process by comprehensively adjusting the injection amount, injection timing and injection law of the oil injector a11, the oil injector b12 and the ammonia fuel injector 7; at the same time, the opening degree of the EGR flow regulating valve 28 and the back pressure regulating valve 22 is flexibly adjusted to realize the optimization of engine operating performance. The diesel / ammonia dual fuel engine of the patent can realize two working modes of pure diesel combustion mode and dual fuel combustion mode, and the specific implementation scheme is:

[0034] (1) In the pure diesel combustion mode: because the diesel fuel combustion mode is compression ignition, the distribution state in the cylinder is locally high concentration, therefore, only low temperature EGR is used in the pure diesel mode, the opening angle of the EGR flow regulating valve 28 is [90*XZ]℃A, the proportion of inert gas in the cylinder is adjusted according to the engine load state, the highest temperature and pressure of combustion are reduced, and the generation of nitrogen oxides in the exhaust pollutants is reduced. When the diesel / ammonia dual fuel engine is in the starting, idling and low load working condition, the oil injector b12 is in the working state, the injection start point of the oil injector b12 is before the compression top dead center, and gradually delays with the increase of load to optimize the combustion timing, by using the small flow injector and making the oil injector b12 work in the linear characteristic area, using less fuel to form an easy-to-burn environment in the cylinder, and realizing accurate control of the injection amount through multiple injection of diesel, the engine economy is improved; when the engine is in the medium and high load working condition, in order to solve the problem that the injection amount of the oil injector b12 cannot meet the fuel flow demand of the engine, the oil injector a11 and the oil injector b12 are used simultaneously, and the oil injector a11 is ensured to work in the linear characteristic area, the oil injector a11 starts to inject before the compression top dead center, and the injection start point gradually delays with the increase of load to optimize the combustion timing, at the same time, in order to prevent the oil injector b12 from generating carbon deposition or ablation due to high temperature combustion, the oil injector b12 injects diesel when the engine output power is greater than 75% of the rated power, which meets the power demand of the diesel / ammonia dual fuel engine.

[0035] (2) In dual-fuel combustion mode: In dual-fuel combustion mode, the diesel / ammonia dual-fuel engine is in the medium and high load operation stage, and the high and low temperature EGR cooperative working mode is adopted to adjust the fuel activity state in the cylinder. The opening angle of the back pressure regulating valve 22 is [60*(1-XR)]℃A, and the opening angle of the EGR flow regulating valve 28 is [90*XZ]℃A. When the load is low, the exhaust back pressure is increased by adjusting the back pressure regulating valve 22, the high temperature exhaust gas retention rate in the cylinder is increased, the initial temperature of ammonia fuel combustion in the cylinder is increased, ammonia fuel combustion is promoted, and as the load increases, the opening angle of the back pressure regulating valve 22 gradually decreases, the opening angle of the EGR flow regulating valve 28 gradually increases, the proportion of low temperature exhaust gas in the intake gas is increased, the number of inert gas molecules in the cylinder is increased, the highest temperature and pressure of combustion are reduced, and the emission of nitrogen oxides in the exhaust is reduced. The ammonia fuel injector 7 and the oil injector b12 work cooperatively, the ammonia fuel injector 7 sprays between 10℃A-40℃A after the exhaust valve 13 is closed, and gradually advances as the engine load increases, the injection end is between 10℃A-20℃A before the intake valve 10 is closed, and the total heat value of the sprayed ammonia fuel accounts for 80%-85% of the total fuel heat value; The oil injector b12 sprays multiple times before the compression top dead center and in the latter half of the compression stroke, and the heat value of the sprayed diesel fuel accounts for 15%-20% of the total fuel heat value. The ammonia fuel is mixed with air in the intake manifold 8 and enters the cylinder. In order to improve the combustion activity of ammonia fuel, the high and low temperature EGR adjustment strategy is adopted, multiple diesel injections are made, multiple combustible areas are formed in the cylinder, uniform combustion in the cylinder is achieved, flame propagation speed is accelerated, combustion is completed in a short time, emissions are reduced, and at the same time, the engine provides strong power.

Claims

1. A diesel and ammonia dual-fuel engine combustion system based on high and low temperature EGR active reforming, characterized by: The engine comprises a cylinder wall, a cylinder head, a piston, a diesel fuel tank, an ammonia fuel storage tank, and a high and low temperature EGR system. The cylinder wall, cylinder head, and piston form a cylinder. The cylinder head is provided with an injector a, an injector b, an intake valve, and an exhaust valve. The cylinder is connected to the intake manifold via the intake valve, and the cylinder is connected to the exhaust manifold via the exhaust valve. The intake manifold is connected to the intake manifold, and the exhaust manifold is connected to the exhaust manifold. The diesel fuel tank is connected to the fuel pump, the fuel filter, the fuel injection pump, and the high-pressure fuel rail in sequence. The high-pressure fuel rail is connected to the fuel injector a, the fuel injection pump, and the high-pressure fuel rail respectively. b, the ammonia fuel storage tank is sequentially connected to the ammonia fuel delivery pump, the ammonia fuel filter, the ammonia injection pump, and the ammonia fuel rail, the ammonia fuel rail is connected to the ammonia fuel injector, the high and low temperature EGR system includes an EGR pipeline system, the two ends of the EGR pipeline system are respectively connected to the intake manifold and the exhaust manifold, an EGR cooler and an EGR flow regulating valve are provided on the EGR pipeline system, an air flow meter is installed on the intake manifold before the EGR pipeline system, and a back pressure regulating valve is installed on the exhaust manifold after the EGR pipeline system; Injector a and injector b adopt a high-low flow step design, and the maximum flow of injector a is much greater than the maximum flow of injector b. The nozzle of injector a is a single-spray hole design, and the nozzle of injector b is a multi-spray hole non-uniform design.

2. The diesel and ammonia dual-fuel engine combustion system based on high and low temperature EGR active reforming according to claim 1 is characterized by: Injector a is installed vertically on the cylinder head, with its axis coinciding with the center line of the cylinder; injector b is installed vertically on the cylinder head, with its axis parallel to the axis of injector a; the ammonia fuel injector is installed obliquely on the intake manifold, with the ammonia fuel injection direction pointing along the intake manifold into the cylinder.

3. The diesel and ammonia dual-fuel engine combustion system based on high and low temperature EGR active reforming according to claim 1 is characterized by: The ammonia fuel injector is a single-hole injector structure with mid-section heating and an axis needle type. A heating resistor is installed in the middle of the ammonia fuel injector.

4. The diesel and ammonia dual-fuel engine combustion system based on high and low temperature EGR active reforming according to claim 1 is characterized by: The back pressure regulating valve opening angle range is 0~60℃A. When the opening angle is 0℃A, the back pressure regulating valve is in a fully open state. When the opening angle is 90℃A, the back pressure regulating valve is in a fully closed state. The relationship between the back pressure regulating valve opening angle and the engine output power ratio X is [60*(0.5-X) R ]℃A.

5. The diesel and ammonia dual-fuel engine combustion system based on high and low temperature EGR active reforming according to claim 1 is characterized by: The opening angle range of the EGR flow control valve is 0-90°A. When the opening angle is 0°A, the EGR flow control valve 28 is in a fully closed state. When the opening angle is 90°A, the EGR flow control valve is in a fully open state. The relationship between the opening angle of the EGR flow control valve and the engine output power ratio X is [90*X Z ]℃A.

6. A combustion method for a diesel and ammonia dual-fuel engine combustion system based on high and low temperature EGR active reforming according to claim 1, characterized in that: Including pure diesel combustion mode: only low temperature EGR is used, and the opening angle of the EGR flow control valve is [90*X Z ]℃A, when the diesel / ammonia dual-fuel engine is in starting, idling and low-load conditions, injector b is in working state, the injection start point of injector b is before compression top dead center, and is delayed as the load increases; when the engine is in medium and high load conditions, injector a and injector b are used in simultaneous working mode, and injector a is operated in the linear characteristic area, injector a starts to inject before compression top dead center, and the injection start point is delayed as the load increases. Injector b injects diesel when the engine output power is greater than 75% of the rated power, meeting the power requirements of the diesel / ammonia dual-fuel engine.

7. The combustion method of a diesel and ammonia dual-fuel engine combustion system based on high and low temperature EGR active reforming according to claim 6, characterized in that: Including dual fuel combustion mode: diesel / ammonia dual fuel engine is in the medium and high load operation stage, and the high and low temperature EGR is used to work together to adjust the fuel activity state in the cylinder, and the back pressure regulating valve opening angle is [60*(1-X R )]℃A, the opening angle of the EGR flow control valve is [90*X Z ]℃A, when the load is low, the exhaust back pressure is increased by adjusting the back pressure regulating valve, the high temperature exhaust gas retention rate in the cylinder is increased, and the initial combustion temperature of the ammonia fuel in the cylinder is increased. As the load increases, the opening angle of the back pressure regulating valve is reduced, the opening angle of the EGR flow regulating valve is increased, the proportion of low temperature exhaust gas in the inlet gas is increased, and the number of inert gas molecules in the cylinder is increased. The ammonia fuel injector and injector b work together. The injection starting point of the ammonia fuel injector is between 10℃A and 40℃A after the exhaust valve is closed, and as the engine load increases The injection endpoint is advanced, between 10℃A and 20℃A before the closing of the intake valve, and the total calorific value of the injected ammonia fuel accounts for 80%-85% of the total fuel calorific value; injector b injects before the compression top dead center and in the second half of the compression stroke, and the calorific value of the injected diesel fuel accounts for 15%-20% of the total fuel calorific value. The ammonia fuel is mixed with the air at the intake manifold and then enters the cylinder. A high and low temperature EGR simultaneous adjustment strategy is adopted. By injecting diesel, a flammable area is formed in the cylinder, which makes the cylinder burn evenly and accelerates the flame propagation speed.

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