Combustion system of pre-combustion chamber gas engine with double spark plugs and control method

Abstract

The invention discloses a pre-combustion chamber gas engine combustion system with double spark plugs and a control method, belongs to the technical field of gas engines, and solves the technical problems of low combustion speed and high engine thermal load of a traditional spark ignition type natural gas engine. The system comprises a cylinder body, a cylinder cover is arranged at the top of the cylinder body, a cylinder hole is formed in the cylinder body, a piston is arranged in the cylinder hole, a pre-combustion chamber is arranged on the cylinder cover above the axis of the cylinder hole, a main spark plug is arranged in the pre-combustion chamber, and a plurality of first spray holes are formed in the side wall of the pre-combustion chamber. A second spray hole opposite to the combustion center of the main combustion chamber is formed in the bottom of the pre-combustion chamber, and an auxiliary spark plug is arranged on the cylinder cover on one side of the main spark plug and extends to the main combustion chamber. The main spark plug and the auxiliary spark plug can be independently controlled, different combustion control strategies are achieved according to different working conditions of an engine, the in-cylinder combustion speed is effectively controlled, and the problems of low heat efficiency and high exhaust temperature caused by too high or too low combustion speed are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of gas engines, and more specifically, to a pre-combustion chamber gas engine combustion system with dual spark plugs and a control method thereof. Background Art

[0002] Low-cost, low-carbon natural gas engine vehicles are increasingly accepted by customers. However, in order to further reduce carbon emissions and reduce customer usage costs, high-efficiency, low-emission, and high-durability natural gas engines are the eternal pursuit of the industry. Traditional spark-ignition natural gas engines have problems such as slow combustion speed and high engine heat load.

[0003] like Figure 1 As shown in the figure, the traditional spark-ignition natural gas engine uses a single spark plug. Spark plug A extends directly into the cylinder from the cylinder head B. Spark plug A is located in the middle. The cylinder head B on both sides of spark plug A is respectively provided with an intake valve C and an exhaust valve D. The combustion organization in the cylinder is realized through the cylinder head airway and the shape of the piston head. Flame propagation is mainly achieved through the flow in the cylinder. For engines with relatively large cylinder diameters, the flame propagation distance is long and the knock tendency is strong. It is difficult to achieve a higher combustion speed through the organization of the flow field in the cylinder, and the EGR rate that can be introduced is quite limited.

[0004] There is an urgent need for a technology to increase the combustion speed in the cylinder, widen the EGR rate, and reduce the engine exhaust temperature. Summary of the invention

[0005] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art. One purpose of the present invention is to provide a pre-combustion chamber gas engine combustion system with dual spark plugs, which can increase the combustion speed and reduce the thermal load of the engine.

[0006] The second object of the present invention is to provide a control method for a pre-combustion chamber gas engine combustion system with dual spark plugs.

[0007] In order to achieve the above-mentioned first object, the present invention provides a dual spark plug pre-combustion chamber gas engine combustion system, comprising a cylinder body, a cylinder head is provided on the top of the cylinder body, a cylinder hole is provided in the cylinder body, a piston is provided in the cylinder hole, a pre-combustion chamber is provided in the cylinder head above the axis line of the cylinder hole, a main spark plug is provided in the pre-combustion chamber, a plurality of first spray holes are evenly arranged and tilted downwardly toward the main combustion chamber, a second spray hole is provided at the bottom of the pre-combustion chamber and faces the combustion center of the main combustion chamber, an auxiliary spark plug is provided in the cylinder head on one side of the main spark plug, and the auxiliary spark plug extends to the main combustion chamber;

[0008] The mixture in the pre-combustion chamber burns rapidly under the ignition action of the main spark plug, forming a high-temperature, high-pressure gas that is ejected through the first and second nozzle holes. The high-speed airflow quickly fills the main combustion chamber to achieve multi-point combustion. When the piston moves downward, the combustion gas can be quickly brought to the remaining gas around the cylinder head due to the reverse squeeze flow.

[0009] As a further improvement, the number of the first spray holes is 4.

[0010] Furthermore, the number of the first spray holes is 6.

[0011] Furthermore, the cylinder head corresponding to each of the cylinder holes is provided with two intake valves and two exhaust valves, and the two intake valves and the two exhaust valves are evenly arranged around the circumference.

[0012] Furthermore, the auxiliary spark plug is located between two exhaust valves.

[0013] Furthermore, the auxiliary spark plug is close to the edge of the cylinder hole.

[0014] Furthermore, the cylinder head is a flat-top cylinder head, and a piston combustion chamber is provided on the top of the piston. The piston combustion chamber is a cavity with a small opening and a large interior. Below the opening of the piston combustion chamber is a throat edge, and the first spray hole is aligned with the wall surface of the throat edge of the piston combustion chamber.

[0015] Furthermore, a cylinder liner is provided in the cylinder hole, and the piston is located in the cylinder liner.

[0016] Furthermore, it also includes an air filter, a turbocharger, a controller, an intercooler, an electronic throttle, a gas and EGR mixer, an intake manifold, an EGR valve, an EGR flowmeter, an EGR cooler, an exhaust manifold, and a post-processor. The air filter is connected to the turbocharger, the intercooler, the electronic throttle, the gas and EGR mixer, and the intake manifold in sequence through an intake pipe. The intake manifold is connected to the cylinder head, and the cylinder head is connected to the exhaust manifold. The exhaust manifold is connected to the turbocharger and the post-processor in sequence through an exhaust pipe. The gas and EGR mixer is connected to the EGR valve, the EGR flowmeter, the EGR cooler, and the exhaust pipe connected to the front end of the turbocharger in sequence through an EGR pipe. The controller is electrically connected to the main spark plug, the auxiliary spark plug, the electronic throttle, the EGR valve, and the EGR flowmeter.

[0017] In order to achieve the above-mentioned second objective, the present invention provides a control method for a pre-combustion chamber gas engine combustion system with dual spark plugs, including the following working conditions:

[0018] When the engine is in a high-load condition with a high EGR rate, the controller controls the main spark plug to discharge and ignite the mixture in the pre-combustion chamber to achieve high-speed combustion;

[0019] When the engine is in a high load area with low EGR rate, in order to control the explosion pressure, the flame propagation speed does not need to be too fast. The controller controls the auxiliary spark plug to discharge first to ignite the mixture in the main combustion chamber. After the first set phase, the controller controls the main spark plug to discharge to ignite the mixture in the pre-combustion chamber to accelerate the combustion in the main combustion chamber.

[0020] When the engine is under low load or idling, the mixture in the pre-combustion chamber is difficult to be ignited effectively due to the large amount of residual exhaust gas. At this time, the controller controls the auxiliary spark plug to discharge at the second set phase to ignite the mixture in the main combustion chamber to ensure stable and efficient combustion of the engine under low load or idling.

[0021] Beneficial Effects

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. The present invention adopts a central pre-combustion chamber structure, in which a main spark plug is arranged. The pre-combustion chamber spray hole combined with the combustion chamber can realize high explosion pressure and low exhaust temperature combustion of the natural gas engine, and achieve a higher EGR rate or air-fuel ratio, effectively decoupling the explosion pressure and exhaust temperature coupling of the traditional large-cylinder engine, which makes it difficult to improve the power and thermal efficiency, and the problem of misfire at a large EGR rate or high air-fuel ratio. The use of this technology can achieve an effective thermal efficiency improvement of more than 1%.

[0024] 2. The present invention adopts an auxiliary spark plug arranged on the exhaust side between the two exhaust valves and directly extended into the cylinder, maintaining the advantages of the traditional single spark plug structure and being used for light load ignition. It can effectively solve the problem that the engine cannot be effectively ignited due to the high amount of residual exhaust gas in the pre-combustion chamber at light load. Combined with the large gap spark plug structure, it can effectively reduce the problem of large combustion cycle fluctuations due to the small gap at light load of the traditional single spark plug.

[0025] 3. The present invention can realize independent control of the main spark plug and auxiliary spark plug of a single cylinder, and implement different combustion control strategies according to different areas of the engine, so as to effectively control the combustion speed in the cylinder and avoid the problems of low thermal efficiency and high exhaust temperature caused by too fast or too slow combustion speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the structure using a traditional single spark plug;

[0027] Figure 2 This is a schematic diagram of the structure of the present invention using dual spark plugs;

[0028] Figure 3 It is a structural schematic diagram of the bottom of the cylinder head in the present invention;

[0029] Figure 4 It is a schematic diagram of the structure of the system in the present invention.

[0030] Among them: 1-cylinder block, 2-cylinder head, 3-piston, 4-pre-combustion chamber, 5-main spark plug, 6-first spray hole, 7-second spray hole, 8-auxiliary spark plug, 9-intake valve, 10-exhaust valve, 11-piston combustion chamber, 12-cylinder liner, 13-air filter, 14-turbocharger, 15-controller, 16-intercooler, 17-electronic throttle, 18-gas and EGR mixer, 19-intake manifold, 20-EGR valve, 21-EGR flowmeter, 22-EGR cooler, 23-exhaust manifold, 24-post-processor, 25-intake pipe, 26-exhaust pipe, 27-EGR pipe. DETAILED DESCRIPTION

[0031] The present invention will be further described below with reference to the specific embodiments in the accompanying drawings.

[0032] See also Figure 2 to Figure 4 A dual spark plug pre-combustion chamber gas engine combustion system comprises a cylinder block 1, a cylinder head 2 is arranged on the top of the cylinder block 1, a cylinder hole is arranged in the cylinder block 1, and a piston 3 is arranged in the cylinder hole. A pre-combustion chamber 4 is arranged in the cylinder head 2 above the axis of the cylinder hole, and a main spark plug 5 is arranged in the pre-combustion chamber 4. The side wall of the pre-combustion chamber 4 is provided with a plurality of first spray holes 6 that are evenly arranged and tilted downward to spray toward the main combustion chamber, and a second spray hole 7 facing the combustion center of the main combustion chamber is arranged at the bottom of the pre-combustion chamber 4. The main combustion chamber is a combustion chamber cavity composed of the piston 2, the cylinder hole and the cylinder head 2. The cylinder head 2 on one side of the main spark plug 5 is provided with an auxiliary spark plug 8, and the auxiliary spark plug 8 extends to the main combustion chamber.

[0033] The mixture in the pre-combustion chamber 4 burns rapidly under the ignition action of the main spark plug 5, forming a high-temperature, high-pressure gas that is ejected through the first spray hole 6 and the second spray hole 7. The high-speed airflow quickly fills the main combustion chamber to achieve multi-point combustion. When the piston 3 moves downward, the combustion gas can be quickly brought to the periphery of the cylinder head 2 to burn the remaining gas due to the reverse squeezing effect.

[0034] In one embodiment, the number of the first spray holes 6 is 4, that is, the pre-combustion chamber adopts a 4+1 single-row hole structure.

[0035] In one embodiment, the number of the first spray holes 6 is 6, that is, the pre-combustion chamber adopts a 6+1 single-row hole structure.

[0036] In one embodiment, the cylinder head 2 corresponding to each cylinder hole is provided with two intake valves 9 and two exhaust valves 10, and the two intake valves 9 and the two exhaust valves 10 are evenly arranged around the circumference.

[0037] Preferably, the auxiliary spark plug 8 is located between the two exhaust valves 10, and the auxiliary spark plug 8 is close to the edge of the cylinder hole. When only the auxiliary spark plug 8 is working, the mixed gas around the auxiliary spark plug 8 is fully burned, and the fully burned gas is discharged first during exhaust, and the remaining part of the incompletely burned gas is used for the next combustion work, which can reduce the combustion temperature in the cylinder and reduce pollution.

[0038] Furthermore, the cylinder head 2 is a flat-top cylinder head, and a piston combustion chamber 11 is provided on the top of the piston 3. The piston combustion chamber 11 is a chamber with a small opening and a large interior. The piston combustion chamber 11 occupies a large proportion of the main combustion chamber, which can enhance the reverse squeeze flow effect when the piston 3 moves downward. Below the opening of the piston combustion chamber 11 is the throat edge, and the first spray hole 6 is aligned with the wall of the throat edge of the piston combustion chamber 11.

[0039] In one embodiment, a cylinder liner 12 is provided in the cylinder hole, and the piston 3 is located in the cylinder liner 12 .

[0040] Specifically, the system further includes an air filter 13, a turbocharger 14, a controller 15, an intercooler 16, an electronic throttle 17, a gas and EGR mixer 18, an intake manifold 19, an EGR valve 20, an EGR flowmeter 21, an EGR cooler 22, an exhaust manifold 23, and a post-processor 24. The air filter 13 is connected to the turbocharger 14, the intercooler 16, the electronic throttle 17, the gas and EGR mixer 18, the intake manifold 19, and the intake manifold 19 in sequence through the intake pipe 25. 9 is connected to the cylinder head 2, the cylinder head 2 is connected to the exhaust manifold 23, the exhaust manifold 23 is connected to the turbocharger 14 and the post-processor 24 in sequence through the exhaust pipe 26, the gas and EGR mixer 18 is connected to the EGR valve 20, the EGR flowmeter 21, the EGR cooler 22 in sequence through the EGR pipe 27, and the exhaust pipe 26 connected to the front end of the turbocharger 14, and the controller 15 is electrically connected to the main spark plug 5, the auxiliary spark plug 8, the electronic throttle 17, the EGR valve 20, and the EGR flowmeter 21.

[0041] A control method for a dual spark plug pre-combustion chamber gas engine combustion system includes the following working conditions:

[0042] When the engine is in a high-load condition with a high EGR rate, the controller 15 controls the main spark plug 5 to discharge and ignite the mixed gas in the pre-combustion chamber 4 to achieve high-speed combustion;

[0043] When the engine is in a high load area with low EGR rate, in order to control the explosion pressure, the flame propagation speed does not need to be too fast. The controller 15 controls the auxiliary spark plug 8 to discharge first to ignite the mixture in the main combustion chamber. After the first set phase, the controller 15 controls the main spark plug 5 to discharge and ignite the mixture in the pre-combustion chamber 4 to accelerate the combustion of the main combustion chamber. The first set phase is 5 to 10 degrees of crankshaft angle.

[0044] When the engine is under low load or idling, the mixture in the pre-combustion chamber 4 is difficult to be effectively ignited due to the large amount of residual exhaust gas. At this time, the controller 15 controls the auxiliary spark plug 8 to discharge in the second set phase to ignite the mixture in the main combustion chamber to ensure that the engine can burn stably and efficiently under low load or idling. Specifically, the second set phase can be calibrated according to the bench test. When the engine is under low load or idling, the engine speed does not change much, and the same second set phase can be used.

[0045] The present invention independently controls the main spark plug and the auxiliary spark plug and implements different combustion control strategies according to different areas of the engine, thereby effectively controlling the combustion speed in the cylinder and avoiding the problems of low thermal efficiency and high exhaust temperature caused by too fast or too slow combustion speed.

[0046] The above are only preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the structure of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A dual spark plug pre-combustion chamber gas engine combustion system, comprising a cylinder block (1), a cylinder head (2) being arranged on the top of the cylinder block (1), a cylinder hole being arranged in the cylinder block (1), a piston (3) being arranged in the cylinder hole, characterized in that: The cylinder head (2) above the axis line of the cylinder hole is provided with a pre-combustion chamber (4), a main spark plug (5) is provided in the pre-combustion chamber (4), a side wall of the pre-combustion chamber (4) is provided with a plurality of first spray holes (6) evenly arranged and tilted downwardly spraying toward the main combustion chamber, a second spray hole (7) facing the combustion center of the main combustion chamber is provided at the bottom of the pre-combustion chamber (4), and an auxiliary spark plug (8) is provided on the cylinder head (2) on one side of the main spark plug (5), and the auxiliary spark plug (8) extends to the main combustion chamber; The mixed gas in the pre-combustion chamber (4) burns rapidly under the ignition action of the main spark plug (5), forming high-temperature, high-pressure gas that is ejected through the first spray hole (6) and the second spray hole (7). The high-speed airflow quickly fills the main combustion chamber to achieve multi-point combustion. When the piston (3) moves downward, the combustion gas can be quickly brought to the periphery of the cylinder head (2) to burn the remaining gas due to the reverse squeezing effect.

2. A dual spark plug pre-combustion chamber gas engine combustion system according to claim 1, characterized in that: The number of the first spray holes (6) is four.

3. A dual spark plug pre-combustion chamber gas engine combustion system according to claim 1, characterized in that: The number of the first spray holes (6) is 6.

4. A dual spark plug pre-combustion chamber gas engine combustion system according to claim 1, characterized in that: The cylinder head (2) corresponding to each cylinder hole is provided with two intake valves (9) and two exhaust valves (10), and the two intake valves (9) and the two exhaust valves (10) are evenly arranged around the circumference.

5. A dual spark plug pre-combustion chamber gas engine combustion system according to claim 4, characterized in that: The auxiliary spark plug (8) is located between the two exhaust valves (10).

6. A dual spark plug pre-combustion chamber gas engine combustion system according to claim 5, characterized in that: The auxiliary spark plug (8) is close to the edge of the cylinder hole.

7. A dual spark plug pre-chamber gas engine combustion system according to any one of claims 1 to 6, characterized in that: The cylinder head (2) is a flat-top cylinder head, and a piston combustion chamber (11) is provided on the top of the piston (3). The piston combustion chamber (11) is a chamber with a small opening and a large interior. Below the opening of the piston combustion chamber (11) is a throat edge, and the first spray hole (6) is aligned with the wall surface of the throat edge of the piston combustion chamber (11).

8. A dual spark plug pre-chamber gas engine combustion system according to claim 1, characterized in that: A cylinder sleeve (12) is arranged in the cylinder hole, and the piston (3) is located in the cylinder sleeve (12).

9. A dual spark plug pre-combustion chamber gas engine combustion system according to claim 1, characterized in that: The invention also comprises an air filter (13), a turbocharger (14), a controller (15), an intercooler (16), an electronic throttle valve (17), a gas and EGR mixer (18), an intake manifold (19), an EGR valve (20), an EGR flow meter (21), an EGR cooler (22), an exhaust manifold (23), and a post-processor (24). The air filter (13) is connected to the turbocharger (14), the intercooler (16), the electronic throttle valve (17), the gas and EGR mixer (18), and the intake manifold (19) in sequence through an intake pipe (25). The intake manifold (19) is connected to the cylinder head (2 ), the cylinder head (2) is connected to the exhaust manifold (23), the exhaust manifold (23) is connected to the turbocharger (14) and the post-processor (24) in sequence through the exhaust pipe (26), the fuel gas and EGR mixer (18) are connected to the EGR valve (20), the EGR flowmeter (21), the EGR cooler (22), and the exhaust pipe (26) connected to the front end of the turbocharger (14) in sequence through the EGR pipe (27), and the controller (15) is electrically connected to the main spark plug (5), the auxiliary spark plug (8), the electronic throttle (17), the EGR valve (20), and the EGR flowmeter (21).

10. A control method for a dual spark plug pre-combustion chamber gas engine combustion system, characterized in that: The following conditions are included: When the engine is in a high-load operating condition with a high EGR rate, the controller (15) controls the main spark plug (5) to discharge and ignite the mixed gas in the pre-combustion chamber (4) to achieve high-speed combustion; When the engine is in a high load region with a low EGR rate, in order to control the explosion pressure, the flame propagation speed does not need to be too fast. The controller (15) controls the auxiliary spark plug (8) to discharge first to ignite the mixed gas in the main combustion chamber. After the first set phase is continued, the controller (15) controls the main spark plug (5) to discharge to ignite the mixed gas in the pre-combustion chamber (4), thereby accelerating the combustion in the main combustion chamber. When the engine is under low load or idling, the mixed gas in the pre-combustion chamber (4) is difficult to be effectively ignited due to the large amount of residual exhaust gas. At this time, the controller (15) controls the auxiliary spark plug (8) to discharge at the second set phase to ignite the mixed gas in the main combustion chamber to ensure stable and efficient combustion of the engine under low load or idling.

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