EP4700225A1

EP4700225A1 - Piston, combustion chamber structure, and engine

Info

Publication number: EP4700225A1
Application number: EP24818499.6A
Authority: EP
Inventors: Haiyong Jiang; Shibang KANG; Fuhong Zhang; Maohui SU
Original assignee: Zhejiang Farizon New Energy Commercial Vehicle Group Co Ltd; Zhejiang Geely Holding Group Co Ltd
Current assignee: Zhejiang Farizon New Energy Commercial Vehicle Group Co Ltd; Zhejiang Geely Holding Group Co Ltd
Priority date: 2023-06-08
Filing date: 2024-05-22
Publication date: 2026-02-25
Also published as: WO2024250966A1

Abstract

A piston (100), the top of the piston (100) is provided with a recess (200) and two protruding structures (300), the recess (200) is provided between the two protruding structures (300), and the outer periphery of the cross section of the recess (200) perpendicular to the height direction of the piston is square. The piston (100) can increase the tumble flow of a combustion chamber structure of a methanol engine and improve the combustion efficiency of the methanol engine. A combustion chamber structure (910) and an engine with the piston (100) are also provided.

Description

The present application claims priority to Chinese Patent Applications with application numbers 202310683813.4 and 202321460886.9, both filed on June 8, 2023 , the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present application relates to the technical field of pistons, and in particular to a piston, a combustion chamber structure, and an engine.

BACKGROUND

In the current commercial vehicle engine field, the development of engines suitable for methanol fuel is usually based on traditional diesel engine platforms. However, since diesel engines adopt compression ignition and diffusion combustion mode, intake ports of the cylinder cover are generally tangential or helical swirl intake ports, and the bottom surface of the cylinder cover is a flat structure. In contrast, methanol engines adopt spark ignition and premixed combustion mode, which requires a high tumble flow ratio to increase the turbulent kinetic energy at the end of compression, accelerate flame propagation, and improve combustion efficiency. For methanol engines, the intake ports of the cylinder cover are required to be parallel tumble flow intake ports, and the bottom surface of the cylinder cover is designed to be a roof-shaped structure. These two types of engines have different requirements for the structural design of the combustion system.
In the current engine combustion chambers, most volume is concentrated at the recess on the piston head, which imposes certain constraints on the structural design of the piston. On one hand, the combustion chamber structure composed of the cylinder cover, the piston, and other components is not particularly suitable for the requirements of spark-ignition methanol engines, resulting in low engine combustion efficiency. On the other hand, the compression height of the piston is relatively large, which makes the overall structural size of the engine not compact enough and leads to a large weight. As a moving part, a piston with large weight will also result in large inertia, which affects the noise, vibration, and harshness (NVH) and fuel consumption of the engine.
Therefore, how to conduct an overall consideration for the piston, design a new high-tumble-flow combustion system to improve the combustion efficiency of the engine, while taking into account structural compactness, weight, NVH, and other factors, is a problem that needs to be solved at present.

SUMMARY

The main purpose of the present application is to provide a piston, which aims to increase the tumble flow of the combustion chamber structure of a methanol engine, improve the combustion efficiency of the methanol engine, and take into account structural compactness, weight, and NVH performance at the same time.
To achieve the above purpose, a top of the piston in the present application is provided with a recess and two protruding structures, the recess is provided between the two protruding structures, and an outer periphery of a cross-section of the recess perpendicular to a height direction of the piston is square.
In an embodiment, the outer periphery of the cross-section is provided with two opposite first edges, and one of the two opposite first edges is parallel with one of the two protruding structures.
In an embodiment, one of the two opposite first edges corresponds to one of the two protruding structures.
In an embodiment, an included angle between one side of one of the two protruding structures close to the recess and the cross-section is α, an included angle between one side of one of the two protruding structures away from the recess and the cross-section is β, and 30°≤α≤90° and 30°≤β≤90°.
In an embodiment, 42°≤α≤80° and 42°≤β≤80°.
In an embodiment, 45°≤α≤80° and 45°≤β≤80°.
In an embodiment, α>β.
In an embodiment, a height of the protruding structure is s, and 1 mm≤s≤10 mm.
In an embodiment, 4 mm≤s≤8 mm.
In an embodiment, one side of one of the two protruding structures close to the recess and a side wall of the recess are in a smooth transition.
In an embodiment, any two adjacent sides of the outer periphery of the cross-section are in a smooth transition.
In an embodiment, the piston is provided with a pin hole, and the two protruding structures are distributed along an axis direction of the pin hole.
In an embodiment, a depth of the recess is greater than 0 mm and less than 35 mm.
In an embodiment, a ratio of a compression height of the piston to a maximum outer diameter of the piston is greater than 0.35 and less than 0.7.
In an embodiment, the depth of the recess is greater than 0 mm and less than 15 mm.
In an embodiment, the ratio of the compression height of the piston to the maximum outer diameter of the piston is greater than 0.35 and less than 0.65.
The present application also provides a combustion chamber structure, including:

a cylinder liner;
a cylinder cover provided at the cylinder liner; and
the piston, the piston is provided in the cylinder liner, and a combustion chamber is defined by a bottom of the cylinder cover, a top of the piston, and the cylinder liner.

In an embodiment, the combustion chamber includes a piston combustion chamber provided in the recess of the piston and a cylinder cover combustion chamber provided at the bottom of the cylinder cover, and a volume of the cylinder cover combustion chamber is larger than a volume of the piston combustion chamber.
In an embodiment, the cylinder cover combustion chamber is provided with a first ridge surface and a second ridge surface connected at an angle with the first ridge surface, and a connection between the first ridge surface and the second ridge surface is configured to extend along a direction from one of the two protruding structures to another one of the two protruding structures.
In an embodiment, the combustion chamber structure further includes an intake valve provided at the first ridge surface, an included angle between the first ridge surface and the cross-section is ε, and 15°≤ε≤45°.
In an embodiment, 20°≤ε≤30°.
In an embodiment, the combustion chamber structure further includes an exhaust valve provided at the second ridge surface, wherein an included angle between the second ridge surface and the cross-section is θ, and 15°≤θ≤45°.
In an embodiment, 20°≤θ≤30°.
The present application also provides an engine, including:

an engine main body; and
the combustion chamber structure, and the combustion chamber structure is provided at the engine main body.

In an embodiment, the engine is configured as a methanol engine.
In the technical solution of the present application, the top of the piston is provided with a recess and two protruding structures, and the recess is provided between the two protruding structures. The arrangement of the recess and the protruding structures enables the combustion chamber structure to form a relatively large tumble flow. In addition, the outer periphery of the cross-section of the recess perpendicular to the height direction of the piston is square. With the cooperation of the two protruding structures and the recess of this shape, the combustion chamber structure can form a larger tumble flow and suppress the secondary airflow movement in the later stage, thus greatly improving the combustion efficiency of the methanol engine. It is worth noting that compared with a recess whose cross-section periphery is circular or elliptical, the recess with a square cross-section in the present solution can unexpectedly form a larger tumble flow in the combustion chamber structure when combined with the two protruding structures and has a more significant effect on suppressing the interference of secondary airflow movement in the later stage, thereby achieving a better combustion efficiency of the methanol engine. In addition, due to the structural design of the piston, the recess can be made relatively shallow, and the reduction of the compression height makes the size of the engine in the height direction more compact, reduces the weight, and is more beneficial to the NVH performance. Therefore, the piston takes into account combustion efficiency, structural compactness, NVH performance, and other factors. Furthermore, according to the results of computational fluid dynamics (CFD) simulation analysis, the high-tumble-flow combustion system formed by the piston structure and the roof-shaped cylinder cover has a significantly improved combustion efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to illustrate the technical solutions in the embodiments of the present application or in the related art more clearly, the following briefly introduces the accompanying drawings required for the description of the embodiments or the related art. Obviously, the drawings in the following description are only part of embodiments of the present application. For those skilled in the art, other drawings can also be obtained according to the structures shown in these drawings without any creative effort.

FIG. 1 is a structural schematic diagram of a piston according to an embodiment of the present application.
FIG. 2 is a front view of the piston in FIG. 1.
FIG. 3 is a top view of the piston in FIG. 1.
FIG. 4 is a cross-sectional view along line A-A of the piston in FIG. 3.
FIG. 5 is a cross-sectional view along line B-B of the piston in FIG. 3.
FIG. 6 is a structural schematic diagram of a combustion chamber structure according to an embodiment of the present application.
FIG. 7 is a cross-sectional view along line G-G of the combustion chamber structure in FIG. 6.

Explanation of reference numbers:

[Table 1_sm_0001]

reference number	name	reference number	name
100	piston	600	first ridge surface
200	recess	700	second ridge surface
300	protruding structure	800	intake valve
400	pin hole	900	exhaust valve
500	cylinder cover	910	combustion chamber structure

The realization of the objective, functional characteristics, and advantages of the present application are further described with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solution in the embodiments of the present application. Obviously, the described embodiments are only part of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts are within the scope of the present application.
It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative positional relationship, movement, and the like between components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.
In the present application, unless otherwise clearly specified and limited, the terms "connection" and "fixation" should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can also be an internal connection of two components or an interaction relationship between two components, unless otherwise clearly limited. For those skilled in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.
In addition, if there are descriptions involving "first" and "second" in the embodiments of the present application, the descriptions of "first" and "second" are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and/or" in the whole text includes three parallel schemes. Taking "A and/or B" as an example, it includes scheme A, scheme B, or a scheme where A and B are satisfied at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but must be based on the realization by those skilled in the art. When the combination of technical solutions is contradictory or cannot be realized, it should be considered that such a combination of technical solutions does not exist and is not within the scope required by the present application.
The present application provides a piston, which aims to increase the tumble flow of the combustion chamber structure of a methanol engine, improve the combustion efficiency of the methanol engine, and take into account structural compactness, weight, and noise, vibration, and harshness (NVH) performance at the same time.
With reference to FIG. 1 to FIG. 7, in an embodiment of the present application, the top of the piston 100 is provided with a recess 200 and two protruding structures 300. The recess 200 is provided between the two protruding structures 300. The arrangement of the recess 200 and the protruding structures 300 enables the combustion chamber structure 910 to form a relatively large tumble flow. In addition, the outer periphery of the cross-section of the recess 200 perpendicular to the height direction of the piston 100 is square. With the cooperation of the two protruding structures 300 and the recess 200 of this shape, the combustion chamber structure 910 can form a larger tumble flow and suppress the secondary airflow movement in the later stage, thus greatly improving the combustion efficiency of the methanol engine. It is worth noting that compared with a recess 200 whose cross-section periphery is circular or elliptical, the recess 200 with a square cross-section in the present solution can unexpectedly form a larger tumble flow in the combustion chamber structure 910 when combined with the two protruding structures 300 and has a more significant effect on suppressing the interference of secondary airflow movement in the later stage, thereby achieving a better combustion efficiency of the methanol engine. In addition, due to the structural design of the piston 100, the recess 200 can be made relatively shallow, and the reduction of the compression height makes the size of the engine in the height direction more compact, reduces the weight, and is more beneficial to the NVH performance. Therefore, the piston takes into account combustion efficiency, structural compactness, NVH performance, and other factors. Furthermore, according to the results of computational fluid dynamics (CFD) simulation analysis, the high-tumble-flow combustion system formed by the piston 100 structure and the roof-shaped cylinder cover 500 has a significantly improved combustion efficiency.
It should be pointed out that the "square" mentioned in this document includes but is not limited to a square and a rectangle. The "square" also includes a shape close to a square, that is, the square allows the sides to have a certain curvature and/or the included angles between the sides to be rounded.
In an embodiment, the outer periphery of the cross-section has two opposite first edges, and one first edge is parallel with one protruding structure 300. It can be understood that the outer periphery of the cross-section also has two opposite second edges. One second edge is connected with one end of the two first edges, and the other second edge is connected with the other end of the two first edges. Since the outer periphery of the cross-section is square, the distance between the two second edges does not change or changes to a small extent, which is conducive to the combustion chamber structure 910 forming a relatively large tumble flow. Of course, in other embodiments, one diagonal of the cross-section extends along the direction from one protruding structure 300 to the other protruding structure 300.
In an embodiment, one first edge corresponds to one protruding structure 300. In this way, the two protruding structures 300 are relatively close to the recess 200, which is conducive to forming a relatively large tumble flow in the combustion chamber. Of course, in other embodiments, the distance between the first edge and the protruding structure 300 is greater than 0.5 mm and less than 1.5 mm.
In an embodiment, one protruding structure 300 extends along one first edge. In this way, more airflow passing through the first edge flows through the protruding structure 300, which is conducive to forming a relatively large tumble flow in the combustion chamber and further improving the combustion efficiency of the methanol engine.
In an embodiment, the included angle between the side of the protruding structure 300 close to the recess 200 and the cross-section is α, and the included angle between the side of the protruding structure 300 away from the recess 200 and the cross-section is β, where 30°≤α≤90° and 30°≤β≤90°. In this way, it is conducive to promoting the formation of tumble flow in the combustion chamber and improving the combustion efficiency of the methanol engine.
In an embodiment, 45°≤α≤80° and 45°≤β≤80°. Further, in an embodiment, 45°≤α≤80° and 45°≤β≤80°, which is more conducive to promoting the formation of tumble flow in the combustion chamber and improving the combustion efficiency of the methanol engine. The value of α can be, but is not limited to, 45°, 50°, 55°, 60°, 65°, 70°, 75°, or 80°. The value of β can be, but is not limited to, 45°, 50°, 55°, 60°, 65°, 70°, 75°, or 80°.
In an embodiment, α>β. That is, the slope of the side of the protruding structure 300 close to the recess 200 is steeper, while the slope of the side away from the recess 200 is gentler. This is conducive to promoting the formation of tumble flow in the combustion chamber structure 910 and improving the combustion efficiency of the methanol engine.
In an embodiment, the height of the protruding structure 300 is s, where 1 mm≤s≤10 mm. This is conducive to promoting the formation of tumble flow in the combustion chamber structure 910 and improving the combustion efficiency of the methanol engine. It should be noted that s is the height difference between the highest point of the protruding structure 300 and the periphery of the opening of the recess 200.
In an embodiment, 4 mm≤s≤8 mm. This is more conducive to promoting the formation of tumble flow in the combustion chamber structure 910 and improving the combustion efficiency of the methanol engine. The value of s can be, but is not limited to, 4 mm, 4.5 mm, 5 mm, 5.5 mm, or 6 mm.
In an embodiment, the side of the protruding structure 300 close to the recess 200 and the side wall of the recess 200 are in a smooth transition. In this way, the energy loss of the tumble flow can be reduced, which is conducive to the combustion chamber structure 910 forming a relatively large tumble flow.
In an embodiment, any adjacent two sides of the outer periphery of the cross-section are in a smooth transition. In this way, the energy loss of the tumble flow can be reduced, which is conducive to the combustion chamber structure 910 forming a relatively large tumble flow.
In an embodiment, the piston 100 is provided with a pin hole 400, and the two protruding structures 300 are distributed along the axis direction of the pin hole 400. Of course, in other embodiments, the two protruding structures 300 are respectively in parallel with the pin hole 400.
To save development costs, methanol engines in the prior art are usually further improved based on diesel engines. However, the structure of such methanol engines is also restricted by the structure of the improved base, that is, restricted by the structure of the diesel engine, resulting in a relatively high overall height of the methanol engine. Specifically, the height of the piston 100 of the methanol engine is relatively high, which makes the overall height of the methanol engine relatively high, and further makes the structure of the methanol engine in the height direction not compact enough. Thanks to the structural design of the piston 100 of the present application, the recess 200 can be made relatively shallow, and the reduction of the compression height makes the size of the engine in the height direction more compact, reduces the weight, and is more beneficial to the NVH performance. In an embodiment, the depth of the recess 200 is greater than 0 mm and less than 35 mm. In an embodiment, the depth of the recess 200 is greater than 0 mm and less than or equal to 20 mm. Further, in an embodiment, the depth of the recess 200 is greater than 0 mm and less than or equal to 15 mm. Further, in an embodiment, the depth of the recess 200 is greater than 1 mm and less than or equal to 14 mm. In addition, a relatively small depth of the recess 200 is conducive to reducing the compression height of the piston 100, so that the overall height of the methanol engine using the piston 100 is relatively small, and thus the structure of the methanol engine in the height direction is relatively compact. When the ratio of the compression height of the piston 100 to the maximum outer diameter of the piston 100 is small, the compression height of the piston 100 is relatively small relative to the maximum outer diameter of the piston 100, so that the overall height of the methanol engine using the piston 100 is relatively small, and further the structure of the engine in the height direction is relatively compact. When the ratio is large, the compression height of the piston 100 is relatively large relative to the maximum outer diameter of the piston 100, which is conducive to improving the structural strength of the piston 100. Therefore, when the ratio is greater than or equal to 0.35 and less than or equal to 0.7, the piston 100 not only has a small compression height, which makes the overall height of the methanol engine small and the structure of the methanol engine in the height direction compact, but also has high structural strength, which is conducive to improving the service life of the piston 100. It is worth noting that a small compression height also enables the piston 100 to be made smaller in volume, thus reducing the weight of the piston 100, further reducing the inertia of the piston 100 during movement, and thus improving the NVH performance and fuel consumption of the methanol engine. It can be understood that the piston 100 of the present solution can simultaneously realize making the structure of the methanol engine in the height direction compact, enabling the piston 100 to have high structural strength, improving the combustion efficiency of the spark-ignition methanol engine, and improving the NVH performance and fuel consumption of the methanol engine.
The depth of the recess 200 is shown as h in the drawings of the specification, the compression height is shown as H in the drawings of the specification, and the maximum outer diameter of the piston 100 is shown as D in the drawings of the specification.
In an embodiment, the depth value of the recess 200 can be, but is not limited to, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, or 15 mm.
In an embodiment, the ratio of the compression height of the piston 100 to the maximum outer diameter of the piston 100 is greater than 0.35 and less than 0.65. Similarly, when the ratio is greater than 0.35 and less than 0.65, the piston 100 not only has a small compression height, which makes the overall height of the methanol engine small and the structure of the methanol engine in the height direction compact, but also has high structural strength, which is conducive to improving the service life of the piston 100. Of course, in other embodiments, the ratio of the compression height of the piston 100 to the maximum outer diameter of the piston 100 is greater than 0.35 and less than 0.65.
In an embodiment, the side wall of the recess 200 and the bottom wall of the recess 200 are in a smooth transition. In this way, the resistance of the airflow passing through the recess 200 is small, and the combustion chamber structure 910 using the piston 100 can form a relatively large tumble flow, thus improving the combustion efficiency of the combustion chamber structure 910.
The present application also provides a combustion chamber structure 910. The combustion chamber structure 910 includes a cylinder liner, a cylinder cover 500, and the piston 100. For the specific structure of the piston 100, reference is made to the above-mentioned embodiments. Since the combustion chamber structure 910 adopts all the technical solutions of all the above-mentioned embodiments, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here. The cylinder cover 500 is provided at the cylinder liner, the piston 100 is provided in the cylinder liner, and the bottom of the cylinder cover 500, the top of the piston 100, and the cylinder liner define a combustion chamber.
In an embodiment, the combustion chamber includes a piston combustion chamber provided in the recess 200 of the piston 100 and a cylinder cover combustion chamber provided at the bottom of the cylinder cover 500, and the volume of the cylinder cover combustion chamber is larger than that of the piston combustion chamber. In this way, the combustion chamber is mainly based on the cylinder cover combustion chamber, which is conducive to the formation of tumble flow.
In an embodiment, the cylinder cover combustion chamber is provided with a first ridge surface 600 and a second ridge surface 700 connected at an angle, and the connection between the first ridge surface 600 and the second ridge surface 700 extends along the depth direction of the pin hole 400. In this way, the combustible gas mixture, such as air and methanol, will form a relatively large tumble flow under the extrusion of the first ridge surface 600 and the second ridge surface 700, and the air and methanol are mixed relatively uniformly, which is conducive to improving the combustion efficiency of the engine using the combustion chamber structure 910. Of course, in other embodiments, the specific structural form of the cylinder cover combustion chamber can be designed according to actual needs.
In an embodiment, the combustion chamber structure 910 further includes an intake valve 800 provided at the first ridge surface 600, and the included angle between the first ridge surface 600 and the cross-section is ε, where 15°≤ε≤45°. If ε is too small, the overall width of the methanol engine is compact, the height increases, and the tumble flow ratio increases slightly; if ε is too large, the overall width of the methanol engine increases, the height decreases, and the design requirements for the arrangement of the valve seat rings of the methanol engine are high. Therefore, when 15°≤ε≤45°, the overall width and height of the methanol engine are appropriate, which reduces the requirements for the arrangement of the methanol engine on the vehicle. In addition, the design requirements for the arrangement of the valve seat rings of the methanol engine are reduced, and the methanol engine has a relatively large tumble flow ratio.
In an embodiment, 20°≤ε≤30°. In this way, the overall width and height of the methanol engine are more appropriate, which further reduces the requirements for the arrangement of the methanol engine on the vehicle. In addition, the design requirements for the arrangement of the valve seat rings of the methanol engine are reduced, and the methanol engine has a relatively large tumble flow ratio. The value of ε can be, but is not limited to, 20°, 22°, 25°, 27°, or 30°.
In an embodiment, the combustion chamber structure 910 further includes an exhaust valve 900 provided at the second ridge surface 700, and the included angle between the second ridge surface 700 and the cross-section is θ, where 15°≤θ≤45°. If θ is too small, the overall width of the methanol engine is compact, and the height increases; if θ is too large, the overall width of the methanol engine increases, and the height decreases. Therefore, when 15°≤θ≤45°, the overall width and height of the methanol engine are appropriate, which reduces the requirements for the arrangement of the methanol engine on the vehicle.
In an embodiment, 20°≤θ≤30°. In this way, the overall width and height of the methanol engine are more appropriate, which further reduces the requirements for the arrangement of the methanol engine on the vehicle. The value of θ can be, but is not limited to, 20°, 22°, 25°, 27°, or 30°.
The present application also provides an engine. The engine includes an engine main body and the combustion chamber structure 910. For the specific structure of the combustion chamber structure 910, reference is made to the above-mentioned embodiments. Since the engine adopts all the technical solutions of all the above-mentioned embodiments, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here. The combustion chamber structure 910 is provided at the engine main body.
In an embodiment, the engine is configured as a methanol engine. Further, the engine is configured as a spark-ignition methanol engine. Of course, in other embodiments, the engine can also be a natural gas engine, a gasoline generator, or a hydrogen engine.
The above are only embodiments of the present application, and are not intended to limit the scope of the present application. Under the inventive concept of the present application, any equivalent structural transformation made by using the contents of the specification and the accompanying drawings of the present application, or direct/indirect application in other related technical fields, shall be included in the scope of the present application.

Claims

A piston, characterized in that, a top of the piston is provided with a recess and two protruding structures, the recess is provided between the two protruding structures, and an outer periphery of a cross-section of the recess perpendicular to a height direction of the piston is square.
The piston according to claim 1, wherein the outer periphery of the cross-section is provided with two opposite first edges, and one of the two opposite first edges is parallel with one of the two protruding structures.
The piston according to claim 2, wherein one of the two opposite first edges corresponds to one of the two protruding structures.
The piston according to claim 1, wherein an included angle between one side of one of the two protruding structures close to the recess and the cross-section is α, an included angle between one side of one of the two protruding structures away from the recess and the cross-section is β, and 30°≤α≤90° and 30°≤β≤90°.
The piston according to claim 4, wherein 45°≤α≤80° and 45°≤β≤80°.
The piston according to claim 4, wherein α>β.
The piston according to claim 1, wherein a height of the protruding structure is s, and 1 mm≤s≤10 mm.
The piston according to claim 7, wherein 4 mm≤s≤8 mm.
The piston according to claim 1, wherein:
one side of one of the two protruding structures close to the recess and a side wall of the recess are in a smooth transition; and/or

any two adjacent sides of the outer periphery of the cross-section are in a smooth transition; and/or

the piston is provided with a pin hole, and the two protruding structures are distributed along an axis direction of the pin hole.
The piston according to any one of claims 1 to 9, wherein a depth of the recess is greater than 0 mm and less than 35 mm, and a ratio of a compression height of the piston to a maximum outer diameter of the piston is greater than 0.35 and less than 0.7.
The piston according to claim 10, wherein:
the depth of the recess is greater than 0 mm and less than 15 mm; and/or

the ratio of the compression height of the piston to the maximum outer diameter of the piston is greater than 0.35 and less than 0.65.
A combustion chamber structure, characterized by comprising:
a cylinder liner;

a cylinder cover provided at the cylinder liner; and

the piston according to any one of claims 1 to 11, wherein the piston is provided in the cylinder liner, and a combustion chamber is defined by a bottom of the cylinder cover, a top of the piston, and the cylinder liner.
The combustion chamber structure according to claim 12, wherein the combustion chamber comprises a piston combustion chamber provided in the recess of the piston and a cylinder cover combustion chamber provided at the bottom of the cylinder cover, and a volume of the cylinder cover combustion chamber is larger than a volume of the piston combustion chamber.
The combustion chamber structure according to claim 12, wherein the cylinder cover combustion chamber is provided with a first ridge surface and a second ridge surface connected at an angle with the first ridge surface, and a connection between the first ridge surface and the second ridge surface is configured to extend along a direction from one of the two protruding structures to another one of the two protruding structures.
The combustion chamber structure according to claim 14, further comprising an intake valve provided at the first ridge surface, wherein an included angle between the first ridge surface and the cross-section is ε, and 15°≤ε≤45°.
The combustion chamber structure according to claim 15, wherein 20°≤ε≤30°.
The combustion chamber structure according to claim 14, further comprising an exhaust valve provided at the second ridge surface, wherein an included angle between the second ridge surface and the cross-section is θ, and 15°≤θ≤45°.
The combustion chamber structure according to claim 17, wherein 20°≤θ≤30°.
An engine, characterized by comprising:
an engine main body; and

the combustion chamber structure according to any one of claims 12 to 18, wherein the combustion chamber structure is provided at the engine main body.
The engine according to claim 19, wherein the engine is configured as a methanol engine.