Combustion chamber wall surface pit array structure design method and combustion chamber

Abstract

The invention discloses a combustion chamber wall surface pit array structure design method and a combustion chamber. The method comprises the following steps: extracting a three-dimensional fluid model and carrying out bench test; establishing and verifying an in-cylinder combustion and emission simulation model; performing temperature field bench test on the cylinder cover, the piston and the cylinder sleeve; establishing and verifying a heat transfer simulation model; establishing a heat engine coupling simulation model; parameterization design is conducted on the pit array structures on the piston, the cylinder sleeve and the cylinder cover, a collaborative optimization mathematical model of pit array structure design is established, an optimal solution set is obtained, and typical solutions are selected; key parts in the typical solution are machined, an installation test is carried out, and the optimal pit array structure design scheme is obtained through the test. According to the pit array structure obtained through the collaborative optimization design method, the weight of components can be reduced, a turbulent layer can be formed on the near wall face of the combustion chamber to promote oil-gas mixing, then nitric oxide and particulate matter are reduced, and the combustion performance of an engine is improved.

Description

Technical Field

[0001] The invention relates to an engine combustion chamber, and in particular to a method for collaboratively optimizing the design of a combustion chamber wall surface concave pit array structure and a combustion chamber. Background Art

[0002] In recent years, reducing carbon emissions has become a common pursuit of the world, which requires engines to continue to develop in the direction of low carbonization, cleaning and lightweight.

[0003] In order to meet the above development needs, improving the power density of the engine and the explosion pressure of combustion has become the focus of research. Therefore, developing an efficient and clean combustion system is the key to achieving the above development requirements.

[0004] CN114526151A discloses a combustion chamber and a diesel engine, the bottom of the combustion chamber pit includes a central protrusion of a rotary shape protruding upward and a circumferential annular pit surrounding the central protrusion. The pit of the patent is annular, and the pit is only on the piston structure, and its essence does not achieve the purpose of reducing the weight of the components. CN115355082A discloses a combustion chamber structure of a gas engine with a combustion acceleration function, and the combustion chamber pit is opened on the top of the piston. However, the pit of the patent is an arc structure, connected to the flow increase port, and there is no array feature. CN114810329A discloses a combustion chamber and a gas engine, the circumferential wall surface of the combustion chamber pit includes two main tumble guide walls and two cross tumble guide walls that are alternately and smoothly connected in the circumferential direction, the two main tumble guide walls and the bottom surface of the combustion chamber pit together form an open pit structure, and the two cross tumble guide walls and the bottom surface of the combustion chamber pit together form a constricted pit structure. The patent has a concave groove only on the piston structure, and the structure is only a variation of the piston combustion chamber structure, and does not achieve the goal of reducing the weight of the piston. CN117128105A discloses a piston, a combustion chamber and an engine, wherein the top surface of the piston is provided with a combustion chamber concave groove, and the side walls of the piston surrounding the combustion chamber concave groove are provided with multiple flow channels. The patent has a concave groove only on the piston structure, and the concave groove structure is accompanied by a flow channel structure, and does not involve the optimization of the position, shape, number, etc. of the concave groove. CN 117108395A discloses a combustion chamber, a combustion system, a design method and an engine, wherein the combustion chamber concave groove is alternately provided with ridges protruding toward the central axis of the combustion chamber and indentations recessed toward the central axis away from the combustion chamber on the circumferential side walls surrounding the central boss. The indentations of the patent are only on the piston structure, and do not achieve the goal of reducing the weight of the components. CN213510911U discloses a piston and a diesel engine having the same, wherein the top surface of the piston is provided with a plurality of arcuate pits along the circumferential direction of the piston, the wall surface of one end of the arcuate pit is arcuate, and the other end is connected to the circular pit. The pits in this patent are in an arcuate structure and are connected to the circular pits, and the number and position of the pits are related to the number and position of the injection beams. CN113389634 A discloses a squeeze flow high turbulence centrifugal piston combustion chamber and combustion system, wherein the combustion chamber is composed of a plurality of pits, wherein the plurality of pits are connected to each other on one side close to the center of the piston, and the plurality of pits are arranged at intervals on the side close to the outer edge of the piston. The pit structure in this patent is only a variation of the piston combustion chamber structure, and does not achieve the goal of reducing the weight of the piston.

[0005] In summary, the current pit design for the combustion chamber wall is only reflected in the piston components. Most of the pit structures on the piston are only variations of the piston head structure, without array features and without optimization of the position, shape, number, etc. of the pits. In essence, it does not achieve the purpose of reducing the weight of the piston components. Therefore, in order to fully improve the combustion efficiency of the combustion system and achieve lightweight components, it is particularly important to set the pit structure on the components of the combustion chamber wall. It can provide technical support and theoretical basis for the development and optimization design of the engine combustion chamber system.

[0006] The current pit design of the combustion chamber has the following main deficiencies:

[0007] 1) The pits were only set on the piston, which is one of the components of the combustion chamber, without a systematic analysis of the pit structure, and it is impossible to tell whether the introduction of the pits has a positive or negative impact on the entire combustion chamber system;

[0008] 2) There is no optimization of the position, shape, number, etc. of the pits, especially the coordinated optimization design of the combustion and emission performance, heat transfer and reliability performance of the combustion chamber system;

[0009] 3) There is no effort to achieve lightweighting of key components that make up the combustion chamber. Summary of the invention

[0010] The present invention aims to solve the problems existing in the prior art and provides a collaborative optimization design method for the combustion chamber wall surface pit array structure. The present invention forms a complete and effective collaborative optimization design method for the combustion chamber wall surface pit array structure through systematic means of experimental testing, simulation modeling and analysis, and re-experimental verification of the optimization scheme, which can provide technical support and theoretical basis for the development and optimization design of the engine combustion chamber system.

[0011] In order to solve the above technical problems, the present invention is implemented by adopting the following technical solutions:

[0012] A collaborative optimization design method for a combustion chamber wall surface pit array structure comprises the following steps:

[0013] Step 1, extracting a three-dimensional fluid model of a combustion chamber from a three-dimensional solid model of an assembled engine;

[0014] Step 2, conducting a bench test on the engine to obtain the cylinder pressure curve, heat release rate curve, and power, economy and emission performance indicators;

[0015] Step 3, establishing an engine cylinder combustion and emission simulation model and performing solver settings and calculations; verifying the accuracy of the engine cylinder combustion and emission simulation model through experimental data obtained from the experiment;

[0016] Step 4, performing a temperature field bench test on the cylinder head, piston and cylinder liner of the engine;

[0017] Step 5, establish the heat transfer simulation model of the key components related to the combustion chamber, namely the piston, cylinder liner and cylinder head, and perform the solver settings and calculations;

[0018] Step 6, verifying the accuracy of the heat transfer simulation model of the piston, cylinder liner and cylinder head through temperature field tests of key components;

[0019] Step 7, establish the thermal-engine coupling simulation model of the key components related to the combustion chamber, the piston, the cylinder liner and the cylinder head, and set and calculate the solver;

[0020] Step 8, parameterize the pit array structure on the piston, cylinder liner and cylinder head to construct a sufficiently large design space;

[0021] Step 9, extracting a three-dimensional fluid model for each sample point in the design space according to step 1 and establishing an engine cylinder combustion and emission simulation model and performing solver settings and calculations, and extracting characteristic parameters representing combustion performance and emission performance of each sample point;

[0022] Step 10, further establishing heat transfer simulation models and thermal-mechanical coupling simulation models of key components related to the combustion chamber, such as the piston, cylinder liner, and cylinder head, for each sample point in the design space according to step 5, setting and calculating the solver, and extracting characteristic parameters representing heat transfer characteristics and reliability performance of each sample point;

[0023] Step 11, establish a collaborative optimization mathematical model for the pit array structure design, obtain the optimal solution set, and select no less than 3 groups of typical solutions.

[0024] Step 12, using 3D printing technology to process the key components of the typical solution, the piston, cylinder liner and cylinder head.

[0025] Step 13, install the newly designed key components and repeat the tests of steps 3 and 4.

[0026] Step 14, obtaining the best design scheme of the pit array structure by comparing the experimental data.

[0027] Furthermore, the three-dimensional fluid model in step 1 is composed of the piston top surface, cylinder wall, cylinder head, intake duct, exhaust duct, intake valve, exhaust valve, intake inlet, exhaust outlet, etc.

[0028] Furthermore, the power, economy and emission performance indicators tested by the engine bench test in step 2 mainly include speed, torque and power, fuel consumption rate, engine oil consumption, CO emissions, NO x Emissions, HC emissions, smoke density, etc.

[0029] Furthermore, in step 3, after the calculation of the combustion and emission simulation model in the engine cylinder is completed, the cylinder pressure curve under the last working cycle is extracted and compared with the test data under the same working conditions. The verification standard is: the relative error between the simulation value and the test value is ≤5%.

[0030] Furthermore, in step 4, the temperature field test measurement points are arranged on the cylinder head in a physical object, and the measurement point positions should be distributed in a circle with the center of the nose bridge area of ​​the cylinder head fire surface, and the number of measurement points should not be less than 4. The temperature field test measurement points are arranged on the cylinder liner in a physical object, and the measurement point positions should include the positions of the corresponding pistons at the top dead center, the bottom dead center, and the midpoint of operation, and the number of measurement points should not be less than 3. The temperature field test measurement points are arranged on the piston in a physical object, and the measurement point positions should be distributed in a circle with the center of the combustion chamber, and the number of measurement points should not be less than 3.

[0031] Furthermore, in step 5, the heat transfer simulation model of the piston, cylinder liner and cylinder head adopts the third type of thermal boundary to load the convection heat transfer coefficient and surface temperature.

[0032] Furthermore, the verification standard for the accuracy of the heat transfer simulation model of the piston, cylinder liner and cylinder head in step 6 is: the relative error between the simulation value and the test value is ≤5%.

[0033] Furthermore, the fuel gas pressure loading values ​​of the piston, cylinder liner and cylinder head in step 7 depend on the specific test conditions, and the test conditions should include at least one operating point, namely the maximum torque operating point or the calibration operating point.

[0034] Further, in step 8, a pit array structure is arranged on the top surface of the piston combustion chamber, the fire surface of the cylinder head, and the inner wall of the cylinder liner. And the pit array structure is determined by the position size and shape size of the pit. The pit position of the piston and the cylinder head is based on the center of the physical structure, and the initial pit structure is set at different distances from the center, and the initial pit structure is not less than 2. The pit shape is a sphere, a cone, a cylinder or a polygon, and the shape of any combination of the above. And, the center is a designated point, based on the circular layout, the number of pits is evenly distributed on the circumference, and the number of pits on a single circumference is not less than 4. Further, a pit structure is set on the physical part of the cylinder liner corresponding to the piston top dead center, and the pit shape is a sphere, a cone, a cylinder or a polygon, and the shape of any combination of the above. And, the pit structure is in the same horizontal plane and the number of pits is evenly distributed on the circumference, and the number of pits is not less than 4. Further, the arrangement of the pit structure should be on at least one physical object.

[0035] Furthermore, the characteristic parameters characterizing the combustion performance and emission performance directly extracted or indirectly calculated by the simulation model in step 9 include the in-cylinder pressure curve, the in-cylinder heat release rate curve, the in-cylinder average temperature curve, the in-cylinder average turbulent kinetic energy curve, indicated fuel consumption, indicated thermal efficiency, CO emissions, NOx emissions, HC emissions, smoke density, etc.

[0036] Furthermore, in step 10, the characteristic parameters characterizing the heat transfer characteristics and reliability performance directly extracted or indirectly calculated by the simulation model include the maximum temperature, the maximum thermal stress, the maximum thermal-mechanical coupling stress, the minimum safety factor, etc.

[0037] Furthermore, the objective function in the collaborative optimization mathematical model of the pit array structure design in step 11 should include indicated thermal efficiency, maximum thermal stress, and minimum safety factor.

[0038] Furthermore, the software involved in the collaborative optimization of the pit array structure include CONVERGE, UG, HYPERMESH, ABAQUS, FEMFAT, and MATLAB.

[0039] Furthermore, the UG software is used to complete the three-dimensional parametric modeling of the real object and the extraction of the fluid domain and other model processing work; the CONVERGE software is used to complete the establishment of the in-cylinder combustion and emission simulation model; the HYPERMESH software is used to complete the division of the component mesh; and the ABAQUS software is used to complete the establishment of the piston, cylinder liner and cylinder head heat transfer simulation model and thermal-mechanical coupling simulation; the FEMFAT software is used to calculate and obtain the reliability index of the components, that is, the minimum safety factor, and finally the collaborative optimization mathematical model of the pit array structure design is completed in the MATLAB software.

[0040] The beneficial effects of the present invention include:

[0041] Ming has formed a complete and effective collaborative optimization design method for the combustion chamber wall pit array structure by setting pit array structures on the piston, cylinder liner and cylinder head, and combining parametric modeling, simulation analysis, experimental testing and other means. This method can objectively, systematically and quantifiably verify the effectiveness of the structural design, and can provide technical support and theoretical basis for the development and optimization design of the engine combustion chamber system. Specifically:

[0042] (1) By setting up a pit array structure on the piston, cylinder liner and cylinder head, the weight of the components is reduced, which can meet the future lightweight development needs of the entire machine and reduce fuel consumption;

[0043] (2) By setting a dimple array structure on the combustion chamber wall, the oil-gas mixing process in the cylinder is changed, which can promote the formation of vortices around the dimple structure, making the oil-gas mixing more uniform, improving the combustion and emission performance of the engine, and meeting the future low-carbon and clean development needs of the whole machine;

[0044] (3) This method can evaluate the design of the pit array structure from a theoretical and practical perspective, objectively and systematically, and has reference quantitative data, and has high feasibility and feasibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The present invention will be further described below in conjunction with the accompanying drawings:

[0046] Figure 1 is a flow chart of the method of the present invention;

[0047] Figure 2 is a flow chart of a method according to an embodiment of the present invention;

[0048] Figure 3 It is a schematic diagram of the assembly of piston, cylinder liner and cylinder head parts; in the figure: the figure numbers in the figure are: 1-cylinder head, 2-cylinder head pit, 3-intake hole, 4-exhaust hole, 5-injector hole, 6-cylinder liner, 7-cylinder liner pit, 8-piston, 9-piston pit.

[0049] Figure 4 is a schematic diagram of a piston;

[0050] Figure 5 is a schematic diagram of a cylinder head;

[0051] Figure 6 Schematic diagram of the cylinder liner. DETAILED DESCRIPTION

[0052] The following is a detailed description of an embodiment of the present invention in conjunction with the accompanying drawings. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0053] See also Figure 1 and Figure 2 The flowchart shown in the figure is taken as an example to illustrate the collaborative optimization design of the dimple array structure on the combustion chamber wall of a diesel engine. The design method includes the following steps:

[0054] 1) Extract the three-dimensional fluid model of the combustion chamber from the assembled three-dimensional solid model of the engine. The three-dimensional fluid model is composed of the piston top surface, cylinder wall, cylinder head, intake duct, exhaust duct, intake valve, exhaust valve, intake inlet, exhaust outlet, etc.

[0055] 2) Test the engine on a bench to obtain the cylinder pressure curve, heat release rate curve, and power, economy, and emission performance indicators. The power, economy, and emission performance indicators tested on the bench mainly include speed, torque and power, fuel consumption rate, engine oil consumption, CO emissions, NO x Emissions, HC emissions, smoke density, etc.

[0056] 3) Establish the combustion and emission simulation model in the engine cylinder and set up and calculate the solver, and verify the accuracy of the combustion and emission simulation model in the engine cylinder through the test data obtained from the test. The verification standard is: after the calculation of the combustion and emission simulation model in the engine cylinder is completed, extract the cylinder pressure curve under the last working cycle and compare it with the test data under the same working conditions. The relative error between the simulation value and the test value is ≤5%.

[0057] 4) Conduct temperature field bench tests on the cylinder head, piston and cylinder liner of the engine. The temperature field test measuring points shall be arranged on the cylinder head in a circular distribution with the center of the nose bridge area of ​​the cylinder head fire surface, and there shall be no less than 4 measuring points. The temperature field test measuring points shall be arranged on the cylinder liner in a circular distribution with the corresponding piston at the top dead center, bottom dead center and midpoint of operation, and there shall be no less than 3 measuring points. The temperature field test measuring points shall be arranged on the piston in a circular distribution with the center of the combustion chamber, and there shall be no less than 3 measuring points.

[0058] 5) Establish heat transfer simulation models of key components related to the combustion chamber, such as piston, cylinder liner and cylinder head, and set up and calculate the solver. Use the third type of thermal boundary to load the convective heat transfer coefficient and surface temperature in the simulation model.

[0059] 6) The accuracy of the heat transfer simulation model of the piston, cylinder liner and cylinder head is verified through temperature field tests on key components. The verification standard is: the relative error between the simulation value and the test value of the heat transfer simulation model of the piston, cylinder liner and cylinder head is ≤5%.

[0060] 7) Establish a thermal-engine coupling simulation model of the key components related to the combustion chamber, including the piston, cylinder liner and cylinder head, and set up and calculate the solver. The fuel gas pressure loading values ​​of the piston, cylinder liner and cylinder head depend on the specific test conditions. The test conditions should contain at least one operating point, namely the maximum torque operating point or the calibration operating point.

[0061] 8) Perform parameterized design on the pit array structure on the piston, cylinder liner and cylinder head to build a sufficiently large design space. Specifically, the pit array structure is arranged on the top surface of the piston combustion chamber, the fire surface of the cylinder head and the inner wall of the cylinder liner, such as Figure 3As shown. The pit array structure is determined by the position size and shape size of the pit. The position of the pits of the piston and the cylinder head is based on the center of the physical structure. The initial pit structure is set at different distances from the center, and the initial pit structure is not less than 2. The shape of the pit is a sphere, cone, cylinder or polygon, and any combination of the above. In addition, the center is a designated point, and based on the circular layout, the number of pits is evenly distributed on the circumference, and the number of pits on a single circumference is not less than 4. The schematic diagram of the pits on the piston is shown in Figure 4 As shown, the schematic diagram of the pit on the cylinder head is as follows Figure 5 As shown. Further, a pit structure is provided on the actual part of the cylinder sleeve corresponding to the piston top dead center, and the pit shape is a sphere, a cone, a cylinder or a polygon, or any combination of the above shapes. In addition, the pit structure is in the same horizontal plane and is evenly distributed on the circumference, and the number of pits is not less than 4. The schematic diagram of the pits on the cylinder sleeve is as shown Figure 6 Furthermore, the arrangement of the pit structure should be on at least one object.

[0062] 9) For each sample point in the design space, extract the three-dimensional fluid model according to step (1) and establish the engine cylinder combustion and emission simulation model and perform solver settings and calculations, and extract the characteristic parameters representing the combustion performance and emission performance of each sample point. The characteristic parameters representing the combustion performance and emission performance directly extracted or indirectly calculated by the simulation model include the cylinder pressure curve, cylinder heat release rate curve, cylinder average temperature curve, cylinder average turbulent kinetic energy curve, indicated fuel consumption, indicated thermal efficiency, CO emissions, NOx emissions, HC emissions, smoke density, etc.

[0063] 10) Further, for each sample point in the design space, a heat transfer simulation model and a thermal-mechanical coupling simulation model of the key components related to the combustion chamber, the piston, the cylinder liner, and the cylinder head are established according to step (5), and the solver is set and calculated, and the characteristic parameters representing the heat transfer characteristics and reliability performance of each sample point are extracted. The characteristic parameters representing the heat transfer characteristics and reliability performance directly extracted or indirectly calculated by the simulation model should include the maximum temperature, the maximum thermal stress, the maximum thermal-mechanical coupling stress, the minimum safety factor, etc.

[0064] 11) Establish a collaborative optimization mathematical model for the design of the pit array structure, obtain the optimal solution set, and select no less than 3 groups of typical solutions. The objective function in the collaborative optimization mathematical model should include indicated thermal efficiency, maximum thermal stress, and minimum safety factor.

[0065] 12) The key components of the typical solution, piston, cylinder liner and cylinder head, are processed through 3D printing technology.

[0066] 13) Install the newly designed key components and repeat the tests in steps 2) and 4).

[0067] 14) Obtain the optimal pit array structure design scheme through experimental data comparison.

Claims

1. A method for designing a combustion chamber wall pit array structure, characterized in that: The steps include: Step 1, extracting a three-dimensional fluid model of a combustion chamber from a three-dimensional solid model of an assembled engine; Step 2, conducting a bench test on the engine to obtain the cylinder pressure curve, heat release rate curve, and power, economy and emission performance indicators; Step 3, establishing an engine cylinder combustion and emission simulation model and performing solver settings and calculations; verifying the accuracy of the engine cylinder combustion and emission simulation model through experimental data obtained from the experiment; Step 4, performing a temperature field bench test on the cylinder head, piston and cylinder liner of the engine; Step 5, establish the heat transfer simulation model of the key components related to the combustion chamber, namely the piston, cylinder liner and cylinder head, and perform the solver settings and calculations; Step 6, verifying the accuracy of the heat transfer simulation model of the piston, cylinder liner and cylinder head through a temperature field test of key components; Step 7, establishing a thermal-engine coupling simulation model of the key components related to the combustion chamber, the piston, the cylinder liner, and the cylinder head, and performing solver settings and calculations; Step 8, construct a sufficiently large design space to perform parameterized design of the pit array structure on the piston, cylinder liner, and cylinder head; Step 9, extracting a three-dimensional fluid model for each sample point in the design space according to step 1 and establishing an engine cylinder combustion and emission simulation model and performing solver settings and calculations, and extracting characteristic parameters representing combustion performance and emission performance of each sample point; Step 10, further establishing heat transfer simulation models and thermal-mechanical coupling simulation models of key components related to the combustion chamber, such as the piston, cylinder liner, and cylinder head, for each sample point in the design space according to step 5, setting and calculating the solver, and extracting characteristic parameters representing heat transfer characteristics and reliability performance of each sample point; Step 11, establishing a collaborative optimization mathematical model for the design of the dimple array structure to obtain an optimal solution set; Step 12, processing the key components of the typical solution, namely, the piston, the cylinder liner and the cylinder head; Step 13, installing the newly designed key components and repeating the tests of steps 3 and 4; Step 14, obtaining the best design scheme of the pit array structure by comparing the experimental data.

2. The design method according to claim 1, characterized in that: In step 1, the three-dimensional fluid model includes a piston top surface, a cylinder wall, a cylinder head, an intake passage, an exhaust passage, an intake valve, an exhaust valve, an intake inlet, and an exhaust outlet; In step 2, the power, economy and emission performance indicators include speed, torque and power, fuel consumption rate, engine oil consumption, CO emissions, NO x Emissions, HC emissions and smoke; In step 3, the verification of the accuracy of the engine cylinder combustion and emission simulation model includes: The cylinder pressure curve under the last working cycle is extracted and compared with the test data under the same working conditions. The verification standard is: the relative error between the simulation value and the test value is ≤5%.

3. The design method according to claim 1, characterized in that: In step 4, also include: Arrange the temperature field test measuring points on the cylinder head. The measuring points should be distributed in a circle with the center of the nose bridge area of ​​the cylinder head fire surface, and there should be more than 4 measuring points; Arrange the temperature field test measuring points on the cylinder liner. The measuring point positions should include the positions of the corresponding pistons at the top dead center, bottom dead center, and mid-point of operation. There should be more than 3 measuring points. When arranging the temperature field test measuring points on the actual piston, the measuring points should be distributed in a circle with the center of the combustion chamber, and the number of measuring points should be more than 3.

4. The design method according to claim 1, characterized in that: In step 5, the heat transfer simulation model of the piston, cylinder liner and cylinder head adopts the third type of thermal boundary to load the convection heat transfer coefficient and surface temperature; In step 6, the verification standard is: the relative error between the simulation value and the test value is ≤ 5%; In step 7, the fuel gas pressure loading values ​​of the piston, cylinder liner and cylinder head depend on specific test conditions, which include a maximum torque operating point or a calibration operating point.

5. The design method according to claim 1, characterized in that: In step 8, it also includes: The pit array structure is arranged on the top surface of the piston combustion chamber, the fire surface of the cylinder head and the inner wall surface of the cylinder liner respectively, and the pit array structure is determined by the position size and shape size of the pit, wherein the pit position of the piston and the cylinder head is based on the center of the physical structure, and the initial pit structure is set at different distances from the center of the physical structure, and the number of the initial pit structure is more than 2; The shape of the pit is a sphere, a cone and / or a cylinder or a polygon; Taking the center of the physical structure as the designated point, based on a circular layout, a number of pits are evenly distributed on the circumference, and the number of pits on a single circumference is more than 4.

6. The design method according to claim 5, characterized in that: A pit structure is arranged on the physical part of the cylinder sleeve corresponding to the top dead center of the piston. The pit structures are in the same horizontal plane and are evenly distributed on the circumference. The pit structures are arranged on at least one physical object.

7. The design method according to claim 1, characterized in that: In step 9, characteristic parameters characterizing combustion performance and emission performance are directly extracted or indirectly calculated through the simulation model, including in-cylinder pressure curve, in-cylinder heat release rate curve, in-cylinder average temperature curve, in-cylinder average turbulent kinetic energy curve, indicated fuel consumption, indicated thermal efficiency, CO emissions, NOx emissions, HC emissions and smoke density.

8. The design method according to claim 1, characterized in that: In step 10, characteristic parameters characterizing heat transfer characteristics and reliability performance including maximum temperature, maximum thermal stress, maximum thermal-mechanical coupling stress and minimum safety factor are directly extracted or indirectly calculated through the simulation model.

9. The design method according to any one of claims 1 to 8, characterized in that: In step 11, the objective function in the collaborative optimization mathematical model of the dimple array structure design includes indicated thermal efficiency, maximum thermal stress and minimum safety factor.

10. A combustion chamber obtained by a combustion chamber wall surface pit array structure design method as described in any one of claims 1 to 9.

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