Combustion system, gas engine, and combustion system design method

Abstract

A combustion system, comprising a piston (3), a cylinder head (4), a natural gas injector (2) and a fuel injector (1), wherein a combustion chamber (5) is enclosed between the piston (3) and the cylinder head (4), the cylinder head (4) is provided with an air intake duct (41), and the air intake duct (41) is configured to make an airflow in the combustion chamber (5) flow in the form of a vortex in the circumferential direction of the combustion chamber (5); the natural gas injector (2) and the piston (3) are coaxially arranged, and the natural gas injector (2) is provided with a plurality of natural gas spray holes (21) arranged at intervals in a circumferential direction; the intersection point between the central axis of the fuel injector (1) and a first preset plane (100) is a first intersection point, the intersection point between the central axis of the natural gas injector (2) and the first preset plane (100) is a second intersection point, the first preset plane (100) is perpendicular to the central axis of the piston (3), and a connection line between the first intersection point and the second intersection point is a reference line (300); the fuel injector (1) is provided with a first fuel spray hole (11) and a second fuel spray hole (12), the first fuel spray hole (11) and the second fuel spray hole (12) are respectively located on two sides of the reference line (300), an included angle between the central axis of the first fuel spray hole (11) and the reference line (300) is α, and an included angle between the central axis of the second fuel spray hole (12) and the reference line (300) is β, where α>β; a plane which is perpendicular to the reference line (300) and where the central axis of the fuel injector (1) is located is a second preset plane (200), and the first fuel spray hole (11) is located on the side of the second preset plane (200) close to the natural gas injector (2); and an included angle between the spraying direction of a fuel spray from the second fuel spray hole (12) and the tangential direction of an airflow, which flows in the form of a vortex, when flowing through the fuel injector (1) is an acute angle. A fuel spray sprayed from the second fuel spray hole ignites some natural gas jets on the same side as the second fuel spray hole, and under the action of a vortex in the combustion chamber, as the second fuel spray hole continuously sprays fuel, flames formed by the fuel spray igniting the natural gas jets gradually lengthen in the direction of the vortex, so that the fuel spray sprayed from the second fuel spray hole is used to ignite natural gas jets on the side of the natural gas injector facing away from the fuel injector. Further disclosed are a gas engine and a combustion system design method.

Description

Combustion system, gas engine, and combustion system design method

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on January 24, 2024, with application number 202410098925.8, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of engine technology, for example, to a combustion system, a gas engine and a combustion system design method. Background Art

[0003] High-Pressure Direct Injection (HPDI) natural gas engines, also known as high-pressure direct injection (HPDI) engines, inject 5% diesel fuel into the cylinder before compression top dead center (TDC) for ignition. 95% natural gas, injected at 300 bar, is injected into the flame as the primary fuel, burning and producing work. HPDI engines maintain the same power and torque as diesel engines, offering the same dynamic performance as diesel engines, while increasing power and torque by 20% compared to spark-ignition natural gas engines.

[0004] Some HPDI engines employ coupled injectors, meaning that diesel and natural gas injection are performed by the same injector. In HPDI engines employing coupled injectors, because the natural gas channel within the injector must be sealed with diesel fuel, the pressure of the gas rail determines the injection pressure of both diesel and natural gas. Due to the difficulty of gas rail machining, the current pressure is relatively low. While this reduces diesel consumption, the overall injection duration is longer, resulting in poor diesel atomization.

[0005] To this end, a related technology offers a dual-injector combustion system, with natural gas injectors positioned in the center of the combustion chamber and fuel injectors positioned at the edge, allowing for independent diesel and natural gas injection. However, if a dual-injector combustion system ignites a larger natural gas stream with a smaller diesel stream, the natural gas stream facing away from the fuel injector will have difficulty igniting, resulting in lower heat exchange efficiency and poor emissions. Summary of the Invention

[0006] The present application provides a combustion system, a gas engine and a combustion system design method, which can achieve the effect of better igniting multiple natural gas mist beams with a minimum of fuel mist beams, shorten the combustion duration, and improve the combustion efficiency of the gas engine.

[0007] The present application provides a combustion system comprising a piston, a cylinder head, a natural gas injector, and a fuel injector. A combustion chamber is defined between the piston and the cylinder head. The cylinder head is provided with an air intake duct, the air intake duct being configured to cause airflow within the combustion chamber to flow in a vortex along the circumference of the combustion chamber. The natural gas injector is coaxially arranged with the piston and is provided with a plurality of natural gas injection holes spaced circumferentially.

[0008] The intersection point of the central axis of the fuel injector and the first preset plane is a first intersection point, and the intersection point of the central axis of the natural gas injector and the first preset plane is a second intersection point. The first preset plane is perpendicular to the central axis of the piston, and the line connecting the first intersection point and the second intersection point is a reference line.

[0009] The fuel injector is provided with a first fuel injection hole and a second fuel injection hole, the first fuel injection hole and the second fuel injection hole are respectively located on either side of the reference line, an angle α is included between the central axis of the first fuel injection hole and the reference line, and an angle β is included between the central axis of the second fuel injection hole and the reference line, where α>β;

[0010] A plane perpendicular to the reference line and on which the central axis of the fuel injector lies is a second preset plane, and the first fuel injection hole is located on a side of the second preset plane close to the natural gas injector; an angle between an injection direction of an oil beam from the second fuel injection hole and a tangent direction of an airflow flowing in a vortex form through the fuel injector is an acute angle.

[0011] In one or more embodiments, the diameter of the first fuel injection hole is D1, the diameter of the second fuel injection hole is D2, and D1>D2.

[0012] In one or more embodiments, a central axis of the first fuel injection hole and a central axis of the second fuel injection hole are coplanar.

[0013] In one or more embodiments, the angle between the central axis of the first fuel injection hole and the central axis of the fuel injector is a first injection cone angle, the angle between the central axis of the second fuel injection hole and the central axis of the fuel injector is a second injection cone angle, the first injection cone angle is equal to the second injection cone angle and both are θ, θ≤90°.

[0014] In one or more embodiments, 5°≤α≤60°, 5°≤β≤60°.

[0015] In one or more embodiments, an angle between a central axis of the natural gas injection hole and a central axis of the natural gas injector is γ, and 60°≤γ≤85°.

[0016] In one or more embodiments, eight natural gas injection holes are provided, and the eight natural gas injection holes are evenly distributed along the central axis of the natural gas injector.

[0017] In one or more embodiments, the central axis of each natural gas injection hole and the central axis of the natural gas injector are both located on a third preset plane, and the fuel injector is located in an area surrounded by two adjacent third preset planes.

[0018] The present application also provides a gas engine, comprising a cylinder body and a combustion system as described in any of the above schemes, wherein the cylinder body is connected to the cylinder head, a piston hole is provided on the cylinder body, and the piston is slidably disposed in the piston hole.

[0019] The present application also provides a combustion system design method, which is applied to the combustion system described in any of the above solutions. The combustion system design method includes:

[0020] Construct a three-dimensional model of the combustion system and perform three-dimensional combustion simulation based on the three-dimensional model of the combustion system;

[0021] If the fuel jet injected from the first fuel injection hole can reach the bottom surface of the natural gas injector and / or the top surface of the piston, reducing the angle between the central axis of the first fuel injection hole and the central axis of the fuel injector;

[0022] If the fuel jet injected from the second fuel injection hole can reach the bottom surface of the natural gas injector and / or the top surface of the piston, reducing the angle between the central axis of the second fuel injection hole and the central axis of the fuel injector;

[0023] If the fuel jet injected from the second fuel injection hole can reach the side of the natural gas injector, increasing the angle between the central axis of the second fuel injection hole and the central axis of the fuel injector;

[0024] If the fuel jet injected by the second fuel injection hole cannot ignite the natural gas jet located on the same side of the reference line as the second fuel injection hole and the natural gas jet on the side of the natural gas injector facing away from the fuel injector, increasing the aperture of the second fuel injection hole;

[0025] If the fuel jet injected by the first fuel injection hole cannot ignite other natural gas jets except the natural gas jet on the same side of the reference line as the first fuel injection hole and on the side of the natural gas injector facing away from the fuel injector, the aperture of the first fuel injection hole is increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG1 is a schematic diagram of a combustion system using a coupled injector provided in one embodiment;

[0027] FIG2 is a schematic diagram of another combustion system using a coupled injector provided in one embodiment;

[0028] FIG3 is a schematic diagram of a combustion system using dual injectors provided in one embodiment;

[0029] FIG4 is a schematic cross-sectional view of a combustion system provided in an embodiment of the present application within a first preset plane;

[0030] FIG5 is a schematic cross-sectional view of another combustion system provided in an embodiment of the present application within a first preset plane;

[0031] FIG6 is a schematic cross-sectional view of a fuel injector provided in an embodiment of the present application within a second preset plane;

[0032] 7 to 9 are state diagrams of a process in which fuel injected by a fuel injector ignites a natural gas stream of a natural gas injector according to an embodiment of the present application;

[0033] FIG10 is a schematic structural diagram of a gas engine provided in an embodiment of the present application;

[0034] FIG11 is a cross-sectional schematic diagram of a combustion system provided in an embodiment of the present application;

[0035] FIG12 is a flow chart of a combustion system design method provided in an embodiment of the present application.

[0036] In the figure: 1000', natural gas injector; 2000', fuel injector; 1, fuel injector; 11, first fuel injection hole; 12, second fuel injection hole; 2, natural gas injector; 21, natural gas injection hole; 3, piston; 4, cylinder head; 41, air intake duct; 5, combustion chamber; 42, intake valve; 6, cylinder liner; 7, cylinder block; 71, piston hole; 100, first preset plane; 200, second preset plane; 300, reference line. DETAILED DESCRIPTION

[0037] The present application is described below in conjunction with the accompanying drawings and embodiments. The embodiments described herein are intended only to explain the present application and are not intended to limit the present application. For ease of description, the accompanying drawings only show portions related to the present application, not all structures.

[0038] In the description of this application, unless otherwise specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections, electrical connections; direct connections, indirect connections through an intermediate medium, and internal connections between two components or interactions between two components. The meanings of the above terms in this application can be understood based on actual circumstances.

[0039] In this application, unless otherwise specified or limited, a first feature being "above" or "below" a second feature may include the first feature being in direct contact with the second feature, or may include the first feature being in contact with the second feature through another feature between them instead of being in direct contact. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0040] In the description of this embodiment, the terms "upper," "lower," "right," and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplified operation. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meanings.

[0041] In one embodiment, some HPDI engines use coupled injectors, i.e., diesel and natural gas injection are performed by the same injector. The arrangement is shown in Figures 1 and 2 . The injector adopts a double-row hole design, wherein the lower row of injection holes are diesel injection holes, and the upper row of injection holes are natural gas injection holes. Multiple natural gas injection holes and multiple diesel injection holes are spaced apart along the circumference of the injector, and the multiple natural gas injection holes and multiple diesel injection holes are distributed in a one-to-one correspondence. The central axis of the natural gas injection hole and the central axis of the corresponding diesel injection hole are located in the same plane and are parallel. The diesel gas beam injected from the diesel injection hole is shorter than the natural gas gas beam injected from the natural gas injection hole.

[0042] In HPDI engines using coupled injectors, the natural gas passages within the injectors must be sealed with diesel fuel. The gas rail pressure determines the injection pressure of both diesel and natural gas. Due to the difficulty of gas rail machining, the current pressure is relatively low. While this reduces diesel usage, the overall injection duration is longer, resulting in poor diesel atomization.

[0043] To this end, another embodiment proposes a dual-injector combustion system, as shown in Figure 3. A natural gas injector 1000' is arranged in the center of the combustion chamber, and a fuel injector 2000' is arranged at the edge. Diesel injection and natural gas injection are separated to solve the problem that the diesel injection pressure is affected by the natural gas rail pressure, thereby achieving the purpose of increasing the diesel injection pressure, shortening the injection duration, and improving the fuel injection atomization effect.

[0044] In the aforementioned dual-injector combustion system, due to the fuel injectors' placement at the edge, diesel injection holes can only be placed facing the natural gas. Positioning them facing away from the natural gas would not only fail to ignite the fuel, but would also result in diesel spraying onto the cylinder liner. If a smaller diesel jet ignites a larger natural gas jet, the natural gas jet facing away from the fuel injector would inevitably have difficulty igniting, resulting in lower heat exchange efficiency and poor emissions.

[0045] As shown in Figures 4 to 11, an embodiment of the present application provides a combustion system comprising a piston 3, a cylinder head 4, a natural gas injector 2, and a fuel injector 1. A combustion chamber 5 is defined between the piston 3 and the cylinder head 4. The cylinder head 4 is provided with an air intake duct 41, which is configured to cause airflow within the combustion chamber 5 to flow in a swirling manner along the circumference of the combustion chamber 5. The natural gas injector 2 is coaxially arranged with the piston 3 and is provided with a plurality of natural gas injection holes 21 spaced circumferentially. Designing the air intake duct 41 so that airflow entering the combustion chamber 5 through the air intake duct 41 flows in a swirling manner along the circumference of the combustion chamber 5 is a related art and will not be further described here.

[0046] The intersection point of the central axis of the fuel injector 1 and the first preset plane 100 is the first intersection point, and the intersection point of the central axis of the natural gas injector 2 and the first preset plane 100 is the second intersection point. The first preset plane 100 is perpendicular to the central axis of the piston 3, and the line connecting the first intersection point and the second intersection point is the reference line 300.

[0047] The fuel injector 1 is provided with a first fuel injection hole 11 and a second fuel injection hole 12. The first fuel injection hole 11 and the second fuel injection hole 12 are respectively located on both sides of the reference line 300. The angle between the central axis of the first fuel injection hole 11 and the reference line 300 is α, and the angle between the central axis of the second fuel injection hole 12 and the reference line 300 is β, where α>β.

[0048] The plane perpendicular to the reference line 300 and on which the central axis of the fuel injector 1 lies is the second preset plane 200. The first fuel injection hole 11 is located on the side of the second preset plane 200 close to the natural gas injector 2. The angle between the injection direction of the fuel beam from the second fuel injection hole 12 and the tangent direction of the airflow flowing in the form of a vortex as it passes through the fuel injector 1 is an acute angle.

[0049] The combustion system has a natural gas injector 2 coaxial with a piston 3, and a fuel injector 1 is arranged on one side of the natural gas injector 2. The first fuel injection hole 11 and the second fuel injection hole 12 are respectively located on both sides of the reference line 300 and α>β. The angle between the injection direction of the oil beam of the second fuel injection hole 12 and the tangent direction of the air flow flowing in the form of a vortex when passing through the fuel injector 1 is an acute angle. The oil beam injected by the second fuel injection hole 12 ignites the part of the natural gas beam on the same side of the second fuel injection hole 12, and under the action of the vortex in the combustion chamber 5, the second fuel injection hole 12 ignites the natural gas beam. The hole 12 continuously sprays oil beams, and the flame formed by the oil beam igniting the natural gas beam gradually becomes longer along the vortex direction, so that the oil beam injected by the second fuel injection hole 12 ignites the natural gas beam on the side of the natural gas injector 2 facing away from the fuel injector 1; the oil beam injected through the first fuel injection hole 11 ignites the remaining natural gas beams, so that the oil beams injected by the fuel injector 1 on both sides of the reference line 300 can achieve the maximum ignition effect, and all natural gas beams are ignited by using the least amount of oil beams, thereby improving the ignition effect of using fuel to ignite natural gas, and having higher thermal efficiency and lower emissions.

[0050] In some embodiments, the diameter of the first fuel injection hole 11 is D1, and the diameter of the second fuel injection hole 12 is D2, where D1>D2. Because the fuel jet injected from the first fuel injection hole 11 is directed against the vortex direction, the vortex-like airflow within the combustion chamber 5 limits the spray distance of the fuel jet injected from the first fuel injection hole 11. By limiting D1>D2, the fuel jet injected from the first fuel injection hole 11 can ignite other natural gas jets located on the same side of the reference line 300 as the second fuel injection hole 12, excluding the natural gas jet on the side of the natural gas injector 2 facing away from the fuel injector 1.

[0051] In some embodiments, 5°≤α≤60°, and 5°≤β≤60°. This prevents the oil jet injected from the first fuel injection hole 11 from contacting the side of the natural gas injector 2, and the oil jet injected from the second fuel injection hole 12 from contacting the side of the natural gas injector 2, thereby extending the service life of the natural gas injector 2.

[0052] α can be any value between 5° and 60°, such as 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, and 60°. β can be any value between 5° and 60°, such as 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, and 60°.

[0053] In some embodiments, the central axis of the first fuel injection hole 11 and the central axis of the second fuel injection hole 12 are coplanar. The angle between the central axis of the first fuel injection hole 11 and the central axis of the fuel injector 1 is the first injection cone angle, and the angle between the central axis of the second fuel injection hole 12 and the central axis of the fuel injector 1 is the second injection cone angle. The first injection cone angle is equal to the second injection cone angle and both are θ, where θ ≤ 90°. This arrangement allows the fuel jet injected from the first fuel injection hole 11 to contact the natural gas jet located on the same side of the reference line 300 as the first fuel injection hole 11, and the fuel jet injected from the second fuel injection hole 12 to contact the natural gas jet located on the same side of the reference line 300 as the second fuel injection hole 12.

[0054] In some embodiments, the combustion chamber 5 includes a combustion chamber pit provided on the top surface of the piston 3, a central boss provided at the bottom of the combustion chamber pit, an annular boss provided on the circumferential side wall of the combustion chamber pit surrounding the central boss, and a first pit formed between the annular boss and the bottom of the combustion chamber pit; the angle between the central axis of the natural gas injection hole 21 and the central axis of the natural gas injector 2 is γ, 60°≤γ≤85°.

[0055] γ can select any value between 60° and 85°, for example, γ can select any value among 60°, 65°, 70°, 75°, 80°, and 85°.

[0056] Such an arrangement enables the natural gas injection hole 21 to inject natural gas into the first pit, and forms a vortex under the drainage effect of the second pit, thereby improving the uniformity of the natural gas in the first pit.

[0057] In some embodiments, the cross-section of the combustion chamber 5 in any predetermined symmetry plane is symmetrically arranged about the central axis of the combustion chamber 5, and the central axis of the combustion chamber 5 is located in the predetermined symmetry plane. In this way, the entire combustion chamber 5 has a symmetrical structure.

[0058] In some embodiments, eight natural gas injection holes 21 are provided, and the eight natural gas injection holes 21 are evenly distributed circumferentially along the central axis of the natural gas injector 2. The eight natural gas injection holes 21 evenly distributed along the circumference of the natural gas injector 2, combined with the symmetrical arrangement of the combustion chamber 5, can improve the uniformity of natural gas in the combustion chamber 5.

[0059] In some embodiments, the central axis of each natural gas injection hole 21 and the central axis of the natural gas injector 2 lie on a third predetermined plane, and the fuel injector 1 is located within the area bounded by two adjacent third predetermined planes. This arrangement ensures that the fuel jets injected by the first and second fuel injection holes 11, 12 ignite all natural gas, improving the ignition efficiency of natural gas ignition using fuel. Assuming there are eight natural gas injection holes 21, the eight natural gas injection holes 21 correspond to eight third predetermined planes, and the plane where the centers of the natural gas injection holes 21 and the central axis of the natural gas injector 2 lie is the third predetermined plane.

[0060] An embodiment of the present application further provides a gas engine comprising a cylinder body 7 and a combustion system according to any of the above-described embodiments. The cylinder body 7 is provided with a piston bore 71, and a piston 3 is axially movable within the piston bore 71. This gas engine has the same technical effects as the above-described combustion system and will not be further described here. The fuel injector 1 of this gas engine can be a diesel injector, and the natural gas injected by the natural gas injector 2 can be methanol, methane, or the like, without limitation. The gas engine also includes an intake valve 42, a cylinder liner 6, and the like.

[0061] FIG12 is a flow chart of a combustion system design method provided in an embodiment of the present application. As shown in FIG10 , an embodiment of the present application further provides a combustion system design method, which includes the following steps:

[0062] S1. Construct a three-dimensional model of the combustion system.

[0063] S2. Perform three-dimensional combustion simulation based on the three-dimensional model of the combustion system.

[0064] S3. Determine whether the fuel jet injected from the first fuel injection hole 11 can reach the bottom surface of the natural gas injector 2 and / or the top surface of the piston. If so, reduce the angle between the central axis of the first fuel injection hole 11 and the central axis of the fuel injector 1 to update the three-dimensional model of the combustion system, and return to S3. If not, execute S4.

[0065] S4. Determine whether the fuel jet injected from the second fuel injection hole 12 can reach the bottom surface of the natural gas injector 2 and / or the top surface of the piston. If so, reduce the angle between the central axis of the second fuel injection hole 12 and the central axis of the fuel injector 1 to update the three-dimensional model of the combustion system, and return to S3. If not, execute S5.

[0066] S5. Determine whether the fuel jet injected from the second fuel injection hole 12 can reach the side of the natural gas injector 2. If so, increase the angle between the central axis of the second fuel injection hole 12 and the reference line 300 to update the three-dimensional model of the combustion system, and return to S3. If not, execute S6.

[0067] S6. Determine whether the fuel jet injected from the second fuel injection hole 12 can ignite the natural gas jet located on the same side of the reference line 300 as the second fuel injection hole 12, as well as the natural gas jet on the side of the natural gas injector 2 facing away from the fuel injector 1. If so, execute S7. If not, increase the aperture of the second fuel injection hole 12 to update the three-dimensional model of the combustion system, and return to S3.

[0068] S7. Determine whether the fuel jet injected from the first fuel injection hole 11 can ignite other natural gas jets located on the same side of the baseline 300 as the first fuel injection hole 11 and excluding the natural gas jet on the side of the natural gas injector 2 facing away from the fuel injector 1. If so, the fuel system design is complete. If not, increase the aperture of the first fuel injection hole 11 to update the three-dimensional model of the combustion system, and return to S3.

[0069] In step S3, the combustion simulation results are used to determine whether the fuel jet injected from the first fuel injection hole 11 can reach the bottom surface of the natural gas injector 2 and / or the top surface of the piston. In step S4, the combustion simulation results are used to determine whether the fuel jet injected from the second fuel injection hole 12 can reach the bottom surface of the natural gas injector 2 and / or the top surface of the piston. In step S5, the combustion simulation results are used to determine whether the fuel jet injected from the second fuel injection hole 12 can reach the side of the natural gas injector 2. In step S6, the combustion simulation results are used to determine whether the fuel jet injected from the second fuel injection hole 12 can ignite the natural gas jet located on the same side of the reference line 300 as the second fuel injection hole 12, as well as the natural gas jet on the side of the natural gas injector 2 facing away from the fuel injector 1. In step S7, the combustion simulation results are used to determine whether the fuel jet injected from the first fuel injection hole 11 can ignite other natural gas jets, excluding the natural gas jet located on the same side of the reference line 300 as the first fuel injection hole 11 and facing away from the fuel injector 1. As for how to make the above judgment based on the combustion simulation results, it can be observed by human eyes and will not be introduced here.

[0070] The combustion system design method provided in this embodiment enables rapid design of combustion systems tailored to the requirements of different engine models, achieving optimized combustion system design through three-dimensional combustion simulation. This method is faster and less costly than experimental selection. By optimizing the combustion system, natural gas and air can be uniformly mixed within the combustion chamber, and ignited uniformly by the fuel injector 1, shortening the combustion duration and improving the engine's thermal efficiency.

Claims

1. A combustion system, comprising a piston (3), a cylinder head (4), a natural gas injector (2) and a fuel injector (1). A combustion chamber (5) is defined between the piston (3) and the cylinder head (4). An air intake passage (41) is provided on the cylinder head (4), and the air intake passage (41) is configured to make the air flow in the combustion chamber (5) flow in a swirling form along the circumferential direction of the combustion chamber (5). The natural gas injector (2) is coaxially arranged with the piston (3), and a plurality of natural gas injection holes (21) are circumferentially and spacedly arranged on the natural gas injector (2). The intersection point of the central axis of the fuel injector (1) and a first preset plane (100) is a first intersection point, and the intersection point of the central axis of the natural gas injector (2) and the first preset plane (100) is a second intersection point. The first preset plane (100) is perpendicular to the central axis of the piston (3), and the line connecting the first intersection point and the second intersection point is a reference line (300). The fuel injector (1) is provided with a first fuel injection hole (11) and a second fuel injection hole (12). The first fuel injection hole (11) and the second fuel injection hole (12) are respectively located on both sides of the reference line (300). The included angle between the central axis of the first fuel injection hole (11) and the reference line (300) is α, and the included angle between the central axis of the second fuel injection hole (12) and the reference line (300) is β, where α > β. The plane perpendicular to the reference line (300) and where the central axis of the fuel injector (1) is located is a second preset plane (200). The first fuel injection hole (11) is located on the side of the second preset plane (200) close to the natural gas injector (2). The included angle between the fuel injection direction of the second fuel injection hole (12) and the air flow tangential direction when the air flow flowing in a swirling form passes through the fuel injector (1) is an acute angle.

2. The combustion system according to claim 1, wherein, The diameter of the first fuel injection hole (11) is D1, and the diameter of the second fuel injection hole (12) is D2, where D1 > D2.

3. The combustion system according to claim 1, wherein, The central axes of the first fuel injection hole (11) and the second fuel injection hole (12) are coplanar.

4. The combustion system according to claim 1, wherein, The included angle between the central axis of the first fuel injection hole (11) and the central axis of the fuel injector (1) is a first injection cone angle, and the included angle between the central axis of the second fuel injection hole (12) and the central axis of the fuel injector (1) is a second injection cone angle. The first injection cone angle is equal to the second injection cone angle and both are θ, where θ ≤ 90°.

5. The combustion system according to claim 1, wherein, 5°≤α≤60°，5°≤β≤60°。 6. The combustion system according to claim 1, wherein, The included angle between the central axis of the natural gas injection hole (21) and the central axis of the natural gas injector (2) is γ, where 60° ≤ γ ≤ 85°.

7. The combustion system according to claim 1, wherein, There are eight natural gas injection holes (21), and the eight natural gas injection holes (21) are evenly distributed circumferentially along the central axis of the natural gas injector (2).

8. The combustion system according to claim 7, wherein, The central axis of each of the natural gas injection holes (21) and the central axis of the natural gas injector (2) are both located in a third preset plane, and the fuel injector (1) is located in the region surrounded by two adjacent third preset planes.

9. A gas engine, comprising a cylinder block (7) and a combustion system according to any one of claims 1 to 8, wherein the cylinder block (7) is connected to the cylinder head (4), and a piston hole (71) is provided on the cylinder block (7), and the piston (3) is slidably disposed in the piston hole (71).

10. A combustion system design method applied to the combustion system according to any one of claims 1 to 8, the combustion system design method comprising: Constructing a three-dimensional model of the combustion system and performing three-dimensional combustion simulation based on the three-dimensional model of the combustion system; In response to the fuel spray from the first fuel injection hole (11) being able to reach at least one of the bottom surface of the natural gas injector (2) or the top surface of the piston, reducing the angle between the central axis of the first fuel injection hole (11) and the central axis of the fuel injector (1); In response to the fuel spray from the second fuel injection hole (12) being able to reach at least one of the bottom surface of the natural gas injector (2) or the top surface of the piston, reducing the angle between the central axis of the second fuel injection hole (12) and the central axis of the fuel injector (1); In response to the fuel spray from the second fuel injection hole (12) being able to reach the side surface of the natural gas injector (2), increasing the angle between the central axis of the second fuel injection hole (12) and the reference line (300); In response to the fuel spray from the second fuel injection hole (12) being unable to ignite the natural gas jets on the same side of the second fuel injection hole (12) as the reference line (300), and the natural gas jets on the side of the natural gas injector (2) facing away from the fuel injector (1), increasing the aperture of the second fuel injection hole (12); In response to the fuel spray from the first fuel injection hole (11) being unable to ignite the natural gas jets on the same side of the first fuel injection hole (11) as the reference line (300) and other natural gas jets except the natural gas jets on the side of the natural gas injector (2) facing away from the fuel injector (1), increasing the aperture of the first fuel injection hole (11).

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