WPDI combustion chamber capable of reducing methane emission, engine and working method
By setting steps, cyclone structure and fish belly structure in the WPDI combustion chamber, the gas flow path is optimized, and the problems of uneven gas distribution and high methane emissions are solved, and more efficient combustion and lower methane emissions are achieved.
Patent Information
- Application Number
- CN202510531568.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-25
- Publication Date
- 2025-08-15
AI Technical Summary
The existing WPDI combustion chamber structure leads to high methane emissions, uneven gas distribution, and high uncombustible fuel emissions, making it difficult to meet engine demand.
Steps, cyclone structures and fish belly structures are arranged between the combustion chamber pit and the side of the piston. The recesses formed by the fish belly structure promote full diffusion and mixing of gas, reducing the diffusion of gas to the side gaps. Combined with the small inclination step design, the gas flow path is optimized, the compression gap ratio is reduced, and the gas and air mixing is promoted.
Improves the uniformity of gas distribution in the combustion chamber, improves thermal efficiency, and reduces the emission of unburned fuel, especially methane emissions.
Smart Images
Figure CN120488317A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of engines, and in particular to a WPDI combustion chamber, an engine and a working method for reducing methane emissions. Background Art
[0002] Natural gas, methanol, hydrogen and other fuels are used as engine fuels to solve the energy crisis and environmental pollution because their combustion products are relatively clean and easier to obtain and cheaper than oil. The direct injection dual-fuel technology (WPDI) mainly uses a small amount of diesel directly injected into the cylinder to ignite the main fuel (natural gas, methanol, hydrogen, etc.) directly injected into the cylinder. The engine has higher thermal efficiency and avoids the detonation problem of traditional spark-ignition engines.
[0003] Taking natural gas WPDI as an example, high methane emissions are a problem that needs to be solved urgently. The existing WPDI combustion chamber structure is shown in the figure below. Figure 1 As shown in the figure, it is characterized by a large-angle step, a small combustion chamber opening diameter, and a large proportion of the compression clearance. The disadvantage of this design is that after the natural gas is injected into the throat and split up and down, the natural gas above the throat is easily guided by the large-angle step and moves towards the compression clearance and the piston side clearance. The gas in the piston side clearance is difficult to be ignited by diesel, which is the main reason for high methane emissions. Figure 2 As shown; In addition, a larger compression clearance will generate a greater negative pressure at the compression clearance position when the piston moves downward, sucking more gas into the compression clearance and the piston side clearance, further increasing methane emissions; Finally, the gas above the throat mainly diffuses into the compression clearance and the piston side clearance, and the gas below the throat mainly diffuses in the bottom pit, which will cause the area above the combustion chamber pit ( Figure 2 The rounded rectangular area (shown by the dotted line) contains less gas, and the gas distribution in the entire combustion chamber is uneven, which will inevitably lead to incomplete combustion of natural gas and is another important cause of methane emissions. This also results in high unburned fuel emissions in the WPDI engine, making it difficult to meet engine requirements. Summary of the Invention
[0004] The purpose of the present invention is to address the defects of the prior art and provide a WPDI combustion chamber, engine and working method for reducing methane emissions. A step, a vortex structure and a fish belly structure are provided between the combustion chamber pit and the piston side. A vortex structure is provided at the end of the step to reduce the diffusion of gas to the side gap and can guide a part of the gas to the center of the combustion chamber to improve the mixing in the cylinder. A fish belly structure is provided between the vortex structure and the top surface of the piston. On the one hand, the recess formed by the fish belly structure is more conducive to the full diffusion and mixing of the gas here. On the other hand, the recess formed by the fish belly structure causes the gas to undergo rotational disturbance here, further reducing the diffusion of gas to the side gap. In addition, by providing the fish belly structure, the proportion of the compression gap can be reduced, and the suction of gas into the compression gap and the piston side gap when the piston moves downward can be reduced, thereby promoting the mixing of gas and air in the combustion chamber, improving thermal efficiency and reducing the emission of unburned fuel.
[0005] The first object of the present invention is to provide a WPDI combustor that reduces methane emissions by:
[0006] It includes a combustion chamber pit, and along the radial direction away from the combustion chamber axis, a step, a vortex structure and a fish belly structure are sequentially provided between the combustion chamber pit and the side surface of the piston. The fish belly structure is a recessed portion sunken in the top surface of the piston, and the tangent of the step is inclined relative to the top surface of the piston. The step and the fish belly structure extend obliquely toward the top surface of the piston to form a vortex structure, and a groove is formed at the connection position between the step and the vortex structure to guide part of the gas flowing through the vortex structure to return toward the axis of the combustion chamber and part of the gas to cross the vortex structure and move toward the fish belly structure.
[0007] Furthermore, the position where the edge of the combustion chamber pit is adjacent to the step is the throat, and along the radial direction of the combustion chamber, the length of the throat from the end of the swirl structure is less than the length of the fish belly structure and less than the length of the combustion chamber axis from the throat.
[0008] Furthermore, a first inclination angle α is formed between the tangent of the step and the plane where the piston top surface is located, and a second inclination angle β is formed between the tangent of the convoluted structure close to the step and the plane where the piston top surface is located, α≤β.
[0009] Furthermore, the convoluted structure is a protrusion located between the step and the fish belly structure, 0<α≤30°, 30°≤β<90°.
[0010] Furthermore, the distance between the top of the gyratory structure and the bottom plate of the cylinder head is H1, and the distance between the bottom of the fish belly structure and the bottom plate of the cylinder head is H2, and H1<H2.
[0011] Further, wherein, 0
[0012] The overall width of the combustion chamber is L, the piston radius is D, and 0.6D≤L≤0.9D.
[0013] Furthermore, the tangent of the swirling structure close to the step side is inclined toward the axis of the combustion chamber, and the swirling structure protrudes from the step and the fish belly structure, the protruding end is a smooth surface, and the bottom surface of the fish belly structure is an arc-shaped curved surface.
[0014] A second object of the present invention is to provide an engine comprising the WPDI combustion chamber for reducing methane emissions as described in the first object.
[0015] A third object of the present invention is to provide a method for operating a WPDI combustor for reducing methane emissions as described in the first object, comprising:
[0016] The gas is injected into the throat at the edge of the combustion chamber pit. The throat diverts the gas. The gas below the throat rotates and diffuses in the combustion chamber pit, while the gas above the throat moves toward the swirling structure under the guidance of the step.
[0017] Under the guidance of the swirling structure, part of the gas that reaches the swirling structure moves back toward the axis of the combustion chamber, and the other part of the gas passes over the swirling structure and moves toward the fish belly structure;
[0018] The gas rotates under the guidance of the fish belly structure, reducing the diffusion of gas to the compression clearance and piston side clearance.
[0019] Furthermore, the gas is guided by a groove at the junction of the step and the gyratory structure, and the groove has a smooth transition.
[0020] Compared with the prior art, the present invention has the following advantages and positive effects:
[0021] In response to the current problem of high unburned fuel emissions in WPDI engines, a step, a vortex structure and a fish belly structure are set between the combustion chamber pit and the piston side. A vortex structure is set at the end of the step to reduce the diffusion of gas to the side gap, and a part of the gas can be diverted to the center of the combustion chamber to improve the mixing in the cylinder. A fish belly structure is set between the vortex structure and the top surface of the piston. On the one hand, the recess formed by the fish belly structure is more conducive to the full diffusion and mixing of the gas here. On the other hand, the recess formed by the fish belly structure causes the gas to undergo rotational disturbance here, further reducing the diffusion of gas to the side gap. In addition, by setting the fish belly structure, the proportion of the compression gap can be reduced, and the suction of gas into the compression gap and the piston side gap when the piston moves downward can be reduced, thereby promoting the mixing of gas and air in the combustion chamber, improving thermal efficiency, and reducing the emission of unburned fuel.
[0022] In addition, the inclination angle of the step is reduced, which reduces the amount of gas diverted to the compression gap and piston side clearance after being diverted through the throat. Combined with the recess formed by the step and the swirl structure, the diffusion of gas to the side clearance is reduced, and part of the gas can be diverted to the center of the combustion chamber to improve the mixing in the cylinder. Through the design of small inclination step + swirl structure + fish belly structure + small compression clearance, the diffusion of gas to the compression gap and piston side clearance is significantly reduced, and the gas and air in the entire combustion chamber are mixed more evenly, the combustion is more complete, the thermal efficiency is higher, and the methane emissions are lower. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.
[0024] Figure 1 It is a schematic diagram of the structure of an existing WPDI combustion chamber in the background technology of the present invention.
[0025] Figure 2 This is a schematic diagram of the existing WPDI combustion chamber structure in the background technology of the present invention for guiding the gas.
[0026] Figure 3 Schematic diagram of the structure of a WPDI combustor for reducing methane emissions in one or more embodiments of the present invention.
[0027] Figure 4 A schematic diagram illustrating the dimensions of a WPDI combustor for reducing methane emissions in accordance with one or more embodiments of the present invention.
[0028] Figure 5 Schematic diagram of gas flow in a WPDI combustor for reducing methane emissions in one or more embodiments of the present invention.
[0029] Among them, 1. Combustion chamber axis; 2. Combustion chamber pit; 3. Throat; 4. Step; 5. Convolute structure; 6. Fish belly structure; 7. Piston top surface; 8. Compression clearance; 9. Piston side clearance; 10. Groove. DETAILED DESCRIPTION
[0030] Example 1
[0031] In a typical embodiment of the present invention, Figure 3-Figure 5 As shown, a WPDI combustor with reduced methane emissions is provided.
[0032] like Figure 1 、 Figure 2As shown, in WPDI engines, such as natural gas WPDI engines, improper combustion chamber structural design can lead to high methane emissions. Based on this, this embodiment provides a WPDI combustion chamber with reduced methane emissions. By combining a low-angle step 4, a swirling structure 5, and a fish-belly structure 6 with a small compression clearance 8, this embodiment improves existing WPDI combustion chambers, namely, the problem of high methane emissions and uneven gas distribution caused by the tendency of gas to move toward the compression clearance 8 and piston side clearance 9. This embodiment alters the gas flow path and distribution, significantly reducing gas diffusion toward the compression clearance 8 and piston side clearance 9. Furthermore, the gas and air in the entire combustion chamber are more evenly mixed, resulting in more complete combustion, improved thermal efficiency, and reduced gas emissions.
[0033] like Figure 3 、 Figure 4 and Figure 5 As shown, the WPDI combustion chamber for reducing methane emissions includes a combustion chamber pit 2 distributed on the piston top surface 7. A step 4, a swirling structure 5 and a fish belly structure 6 are also provided on the piston top surface 7 outside the combustion chamber pit 2. It can be understood that the combustion chamber pit 2 in this embodiment can also be used as a bottom pit, and the part formed by the step 4, the swirling structure 5 and the fish belly structure 6 can be used as an upper pit, which together constitute the pit of the combustion chamber. In this embodiment, for the convenience of description and analysis, the pit below the throat 3 is called the combustion chamber pit 2, and the parts above the throat 3 are named as the step 4, the swirling structure 5 and the fish belly structure 6 respectively.
[0034] Specifically, such as Figure 3 As shown, along the radial direction away from the combustion chamber axis 1, a step 4, a swirl structure 5 and a fish belly structure 6 are sequentially provided between the combustion chamber recess 2 and the piston side. The fish belly structure 6 is a recessed portion sunken in the piston top surface 7. The tangent of the step 4 is inclined relative to the piston top surface 7. The step 4 and the fish belly structure 6 extend obliquely toward the piston top surface 7 to form the swirl structure 5. A groove 10 is formed at the connection position between the step 4 and the swirl structure 5 to guide part of the gas flowing through the swirl structure 5 to return toward the combustion chamber axis 1 and part of the gas to cross the swirl structure 5 and move toward the fish belly structure 6.
[0035] For step 4, combine Figure 3 and Figure 5 The tangent of step 4 is inclined relative to piston top surface 7, guiding the flow of gas. In existing structures, the steeply inclined step 4 causes gas to move toward compression clearance 8 and piston side clearance 9. However, the inclined step 4 in this embodiment changes the initial flow direction of the gas, preventing excessive gas from directly diffusing into the side clearance.
[0036] Regarding the swirling structure 5, a groove 10 is formed at the junction of the step 4 and the swirling structure 5. The swirling structure 5 serves two main functions. First, it reduces the tendency of the gas to diffuse into the side gap, allowing the gas to be blocked and guided by the swirling structure 5 during its flow, thus changing its direction of movement. Second, the groove 10 can redirect a portion of the gas flowing through the swirling structure 5 back toward the combustion chamber axis 1, guiding the gas toward the center of the combustion chamber. This improves the mixing of the gas within the cylinder, making the gas distribution more uniform and facilitating sufficient combustion. At the same time, some of the gas can flow beyond the swirling structure 5 toward the fish belly structure 6, further adjusting the gas distribution.
[0037] The fish-belly structure 6 is a recessed portion recessed into the piston top surface 7. Firstly, this recessed portion facilitates the thorough diffusion and mixing of the gas there, as its unique shape provides greater space and surface area, promoting better contact and mixing between the gas and air. Secondly, the gas undergoes rotational disturbance within the recessed portion, further reducing its diffusion into the side gaps. This allows more of the gas to participate in combustion within the combustion chamber, rather than leaking into the side gaps and remaining unignited. Thirdly, the inclusion of the fish-belly structure 6 reduces the proportion of the compression clearance 8.
[0038] A larger compression clearance 8 generates a greater negative pressure when the piston descends, drawing more gas into the compression clearance 8 and piston side clearance 9, increasing methane emissions. In this embodiment, the fish belly structure 6 increases the diameter of the combustion chamber opening, thereby reducing the proportion of the compression clearance 8. This, in turn, reduces the adverse effects of gas being drawn into the compression clearance 8 and piston side clearance 9 when the piston descends, promoting mixing of gas and air within the combustion chamber, improving thermal efficiency, and reducing unburned fuel emissions.
[0039] Specific, combined Figure 4 and Figure 5 , the overall width of the combustion chamber is L, 0.6D≤L≤0.9D, and D is the piston radius.
[0040] The distance from the combustion chamber axis 1 to the throat 3 is L1. The length of L1 is determined by the injection rail pressure. Lower rail pressure shortens the injection distance, and consequently, L1 decreases. Increasing L1 reduces the proportion of compression clearance 8, minimizing the draw of gas into the side clearance during piston descent. Adjusting L1 adapts to different rail pressures for gas injection, ensuring optimal distribution of gas within the combustion chamber and facilitating subsequent combustion.
[0041] The distance between the throat 3 and the end of the gyratory structure 5 is L2. L2 and the fish-belly structure 6 together determine the gas distribution ratio to the center of the combustion chamber and the fish-belly position. By properly setting the length of L2, the gas distribution can be optimized, so that the gas reaches the appropriate ratio in the center of the combustion chamber and the fish-belly structure 6, thereby promoting better mixing of gas and air and improving combustion efficiency.
[0042] The length of the fish belly structure 6 is L3, which is determined by the proportion of gas allocated to this place. If there is more gas here, the corresponding L3 should also be larger. The length of L3 is adjusted according to the gas proportion.
[0043] In this embodiment, 0<L2<L3<L1<L is controlled.
[0044] A first inclination angle α is formed between the tangent of step 4 and the plane of piston top surface 7. This angle is the inclination angle of step 4. The smaller α, the weaker the ability to direct gas into the side clearance. (0 < α ≤ 30°) In this embodiment, a smaller α can reduce the diffusion of gas into piston side clearance 9, preventing gas leakage into areas where it is difficult to ignite, thereby reducing gas emissions. By controlling the angle range of α, the initial gas flow direction can be optimized, improving gas utilization within the combustion chamber.
[0045] The swirling structure 5 is a protrusion located between the step 4 and the fish-belly structure 6. The protrusion has a smooth end, and the tangent line of the swirling structure 5 near the step 4 is inclined toward the combustion chamber axis 1. This guides the gas flowing from the step 4, causing a portion of the gas to return toward the combustion chamber axis 1 along the inclined tangent line, thereby directing the gas to the center of the combustion chamber, improving mixing in the cylinder and making the gas distribution in the combustion chamber more uniform, which helps to improve combustion efficiency and reduce gas emissions such as methane.
[0046] The end of the protrusion is a smooth surface, which helps to make a part of the gas flowing through the swirl structure 5 return toward the axis 1 of the combustion chamber, and the other part can move smoothly over the swirl structure 5 toward the fish belly structure 6, thereby achieving a reasonable distribution of gas at the center position of the combustion chamber and the position of the fish belly structure 6, so as to meet the gas volume requirements at different positions, further promote the full mixing of gas and air, and improve the combustion effect.
[0047] A tangent line on the side of the convolute structure 5 near the step 4 forms a second inclination angle β with respect to the plane of the piston top surface 7. This angle is the angle between the convolute structure 5 and the horizontal plane. A larger β angle increases the ability to direct the gas toward the center of the combustion chamber, with a range of 30°≤β<90°. A larger β angle facilitates directing the gas to the center of the combustion chamber, promoting centralized mixing of the gas and improving combustion efficiency.
[0048] The distance between the top of the swirling structure 5 and the cylinder head bottom plate is H1. The smaller H1 is, the less gas is allocated to the fish belly position. The distance between the bottom of the fish belly structure 6 and the cylinder head bottom plate is H2. If more gas is allocated here, the corresponding H2 should also be larger. Among them, 0
[0049] The bottom surface of the fish belly structure 6 is an arc-shaped surface with a radius of R. The smaller R is, the stronger the rotation disturbance of the gas here is and the more uniform the mixing is.
[0050] Figure 5 The flow of gas in the combustion chamber in this embodiment is shown. Figure 5 Taking the posture shown in Figure 1 as an example, the gas injected into the throat 3 is split vertically. The gas below the throat 3 rotates and diffuses within the bottom pit. The gas above the throat 3 begins to move upward and rightward, guided by the step 4. Guided by the gyratory structure 5, some of the gas moves toward the center, while some crosses the gyratory structure 5 and moves toward the fish belly. Due to the curved shape of the fish belly structure 6, the gas undergoes a certain rotational motion under its guidance.
[0051] The low-angle step 4 reduces the flow diversion capacity of the gas to the piston side gap 9, which can reduce the movement of the gas to the piston side gap 9, thereby reducing the gas emission caused by the difficulty of igniting the gas in the piston side gap 9; combined with the swirl structure 5, a part of the gas above the throat 3 that may originally move to the side gap is guided to the center of the combustion chamber, making the gas distribution more uniform, improving the mixing situation in the combustion chamber, and allowing the gas and air to come into more complete contact, which is conducive to the combustion reaction, improves the combustion efficiency, and reduces the methane emission caused by incomplete combustion; combined with the arc feature, the gas is caused to form a rotational motion, which enhances the disturbance of the gas, further It promotes the mixing of gas and air, makes combustion more complete, reduces the proportion of the compression gap 8, and reduces the negative pressure generated at the compression gap 8 when the piston moves downward, thereby reducing the gas being sucked into the compression gap 8 and the piston side gap 9, reducing the accumulation of unburned gas at these positions, and reducing methane emissions; it also combines a small compression gap 8, so that the negative pressure generated when the piston moves downward becomes smaller, and the gas sucked into the compression gap 8 and the piston side gap 9 is reduced. At the same time, it also makes the space for the gas and air to mix in the combustion chamber more reasonable, which is beneficial to improving combustion efficiency. For engines using methane as fuel, methane emissions are lower.
[0052] Example 2
[0053] In another typical embodiment of the present invention, Figure 3-Figure 5 As shown, an engine is given.
[0054] The combustion chamber of the engine adopts the WPDI combustion chamber for reducing methane emissions as in Example 1.
[0055] Example 3
[0056] In another typical embodiment of the present invention, Figure 3-Figure 5 As shown, a method for operating a WPDI combustor with reduced methane emissions is provided, using the WPDI combustor with reduced methane emissions as in Example 1.
[0057] A method for operating a WPDI combustor to reduce methane emissions, comprising:
[0058] The gas is injected into the throat 3 at the edge of the combustion chamber pit 2. The throat 3 diverts the gas. The gas below the throat 3 rotates and diffuses in the combustion chamber pit 2. The gas above the throat 3 moves toward the swirling structure 5 under the guidance of the step 4.
[0059] Under the guidance of the swirl structure 5, part of the gas that reaches the swirl structure 5 moves back toward the combustion chamber axis 1, and the other part of the gas passes over the swirl structure 5 and moves toward the fish belly structure 6;
[0060] The combustion gas is guided by the fish belly structure 6 to form a rotation, thereby reducing the diffusion of the combustion gas into the compression clearance 8 and the piston side clearance 9.
[0061] The flute 10 at the junction of the step 4 and the convoluted structure 5 guides the gas, and the flute 10 has a smooth transition. This smooth transition allows the gas to flow more smoothly, reducing resistance and turbulence in the gas flow, optimizing the gas flow path and distribution ratio, and improving the uniformity of the gas-air mixing in the combustion chamber and combustion efficiency.
[0062] Among them, such as Figure 5 As shown, the throat 3 plays a diversion role. The gas above the throat 3 moves toward the swirling structure 5 under the guidance of the step 4. The existence of the step 4 changes the movement direction of the gas, allowing the gas to flow toward the swirling structure 5. The gas reaching the swirling structure 5 moves in different directions under its guidance.
[0063] Guided by the fish-belly structure 6, the gas rotates. This, on the one hand, enhances the gas's own turbulence and ensures a more complete mixing of the gas and air. On the other hand, this rotation, combined with the unique design of the fish-belly structure 6, reduces the diffusion of the gas into the compression clearance 8 and the piston side clearance 9. The rotation of the gas within the fish-belly structure 6 alters its tendency to diffuse into the side clearances, allowing more gas to participate in the combustion process rather than accumulating in the compression clearance 8 and piston side clearance 9, where ignition is difficult. This reduces gas emissions.
[0064] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.
Claims
1. A WPDI combustor for reducing methane emissions, characterized in that: It includes a combustion chamber pit, and along the radial direction away from the combustion chamber axis, a step, a vortex structure and a fish belly structure are sequentially provided between the combustion chamber pit and the side surface of the piston. The fish belly structure is a recessed portion sunken in the top surface of the piston, and the tangent of the step is inclined relative to the top surface of the piston. The step and the fish belly structure extend obliquely toward the top surface of the piston to form a vortex structure, and a groove is formed at the connection position between the step and the vortex structure to guide part of the gas flowing through the vortex structure to return toward the axis of the combustion chamber and part of the gas to cross the vortex structure and move toward the fish belly structure.
2. The WPDI combustor for reducing methane emissions according to claim 1, wherein: The position where the edge of the combustion chamber pit is adjacent to the step is the throat. Along the radial direction of the combustion chamber, the length of the throat from the end of the swirl structure is less than the length of the fish belly structure and less than the length of the combustion chamber axis from the throat.
3. The WPDI combustor for reducing methane emissions according to claim 1 or 2, wherein: A first inclination angle α is formed between the tangent of the step and the plane where the piston top surface is located, and a second inclination angle β is formed between the tangent of the convoluted structure close to the step and the plane where the piston top surface is located, α≤β.
4. The WPDI combustor for reducing methane emissions according to claim 3, wherein: The convoluted structure is a protrusion located between the step and the fish belly structure, 0<α≤30°, 30°≤β<90°.
5. The WPDI combustor for reducing methane emissions according to claim 1, wherein: The distance between the top of the gyroscopic structure and the bottom plate of the cylinder head is H1, and the distance between the bottom of the fish belly structure and the bottom plate of the cylinder head is H2, where H1<H2.
6. The WPDI combustor for reducing methane emissions according to claim 5, wherein: in, 0<H1<H2≤3mm; the overall width of the combustion chamber is L, the piston radius is D, 0.6D≤L≤0.9D.
7. The WPDI combustor for reducing methane emissions according to claim 1, wherein: The tangent of the gyratory structure close to the step is inclined toward the axis of the combustion chamber, and the gyratory structure protrudes from the step and the fish belly structure, the protruding end is a smooth surface, and the bottom surface of the fish belly structure is an arc-shaped curved surface.
8. An engine, characterized in that: The WPDI combustor for reducing methane emissions comprises the WPDI combustor according to any one of claims 1 to 7.
9. A method for operating a WPDI combustor with reduced methane emissions, using the WPDI combustor with reduced methane emissions according to any one of claims 1 to 7, characterized in that: include: The gas is injected into the throat at the edge of the combustion chamber pit. The throat diverts the gas. The gas below the throat rotates and diffuses in the combustion chamber pit, while the gas above the throat moves toward the swirling structure under the guidance of the step. Under the guidance of the swirling structure, part of the gas that reaches the swirling structure moves back toward the axis of the combustion chamber, and the other part of the gas passes over the swirling structure and moves toward the fish belly structure; The gas rotates under the guidance of the fish belly structure, reducing the diffusion of gas to the compression clearance and piston side clearance.
10. The method for operating a WPDI combustor to reduce methane emissions according to claim 9, wherein: The gas is guided by the groove at the junction of the step and the convolute structure, and the groove has a smooth transition.