Cylinder body structure design method of tensile cylinder of medium-and-small-power diesel engine and storage medium

Abstract

The invention discloses a cylinder body structure design method of a tensile cylinder of a medium-and-small-power diesel engine and a storage medium, and belongs to the field of diesel engine cylinder bodies. The method comprises the following steps: performing modal test and modal finite element simulation calculation based on a three-dimensional model, and taking the center of a cylinder hole as an axis; reinforcing ribs which are symmetrically distributed on the cylinder body main bearing seat, the cylinder body head part, the side wall surface of the skirt part and the like are additionally arranged; a cooling water jacket three-dimensional model is extracted, a cylinder cover temperature field and cooling water jacket fluid flow are subjected to coupling calculation, the cooling heat dissipation capacity of the cooling water jacket is improved, and cylinder hole thermal deformation is reduced; a finite element calculation model of the diesel engine cylinder body including a cylinder body, a cylinder cover, a cylinder gasket and a main bearing cover is built, heat engine coupling calculation simulation is carried out, stress and deformation conditions of all key areas of the diesel engine cylinder body are evaluated, and axial force flow transmission of the cylinder body is optimized. According to the method, the influence of a cooling water jacket, a temperature field and stress on the cylinder body is comprehensively considered, fluid, solid and heat are coupled and considered, and simulation analysis is systematically developed to guide design and optimization.

Description

Technical Field

[0001] The invention relates to the field of diesel engine cylinders, and in particular to a cylinder structure design method and a storage medium for a tension-resistant cylinder of a small- to medium-power diesel engine. Background Art

[0002] The diesel engine cylinder block is a key component of the internal combustion engine. Generally speaking, the cylinder block includes the cylinder bore, cooling water jacket, lubricating oil channel and other structures. It is also the main skeleton component for placing the cylinder head, crank connecting rod mechanism, oil pan and other auxiliary mechanisms. During the operation of the diesel engine, the cylinder block bears multiple loads such as cylinder explosion pressure, piston lateral force, main bearing seat pressure, bolt force thermal stress, etc. Its strength and stiffness directly affect the operating performance of the diesel engine.

[0003] For high-strength small and medium-power diesel engines without cylinder liners, cylinder bore deformation is almost inevitable during the assembly and actual operation of the whole machine. If the deformation of the cylinder bore exceeds a certain degree, it may cause oil burning or even cylinder scuffing. Cylinder scuffing refers to the phenomenon that during the operation of the engine, the piston ring or piston and the inner wall moving surface of the cylinder bore have clear and significant wear marks and scratches, and even abnormal performance of metal molten wear. If the engine has cylinder scuffing, the engine will be difficult to start, the output power will be significantly reduced, the air pressure will be insufficient, the loss of lubricating oil will increase, the noise and emission pollution will increase, and the life will be reduced. In severe cases, the engine will be seriously damaged, and even serious accidents may occur. Therefore, cylinder scuffing is a fatal damage to the engine. Once the engine has cylinder scuffing, not only the cylinder, piston, piston ring and other components need to be scrapped, but also a large amount of additional repair and testing time is required, which is undoubtedly a huge loss.

[0004] Since cylinder scuffing failure cannot be repaired by replacing the cylinder liner after the cylinder scuffing failure occurs in the cylinder liner-less diesel engine, cylinder scuffing failure has become one of the main reasons for the failure and scrapping of cylinder liner-less diesel engines. Therefore, improving the cylinder scuffing problem of the engine can not only effectively increase the working life of the engine, reduce exhaust emissions, protect the safety of the operator, and safeguard the corporate brand image. It can also provide important technical references and basis for the achievement and formulation of relevant indicators such as new product quality, performance and cost when developing subsequent new engine products.

[0005] The existing technical solutions for cylinder bodies tend to be based on empirical design. When using CAE-assisted calculations, they focus on design optimization and generally provide specific solutions based on the problems faced or part failures. There is no systematic design process that couples multiple physical fields.

[0006] The control of cylinder bore deformation is currently mainly solved by adding cylinder liners, spraying coatings on cylinder bores, changing cylinder clearance, etc. However, most of these are empirical controls and cannot solve the problem systematically and quantitatively. At the same time, it may take multiple trials and errors and adjustments to achieve a satisfactory effect. For example:

[0007] A cylinder liner and cylinder liner cooling structure disclosed in CN117365777A, a one-piece cylinder liner suitable for a compact multi-cylinder diesel engine disclosed in CN114837843A, and a diesel engine compact aluminum alloy cylinder wet cast iron cylinder liner structure disclosed in CN115355101A all improve the overall strength and stiffness of the cylinder bore by adding a cylinder liner with high material strength to achieve the purpose of improving cylinder pulling. However, the optimization idea of ​​adding a cylinder liner is limited by the spatial size of the cylinder body itself, which is difficult to implement in a compact cylinder body structure and requires a special space for the cylinder liner to be reserved; on the other hand, the material of the cylinder liner is generally a material with a high density, which will increase the weight of the cylinder body; whether it is a large size space occupied or an increase in weight, it runs counter to the current concept of lightweight cylinder body design.

[0008] A surface preparation method for improving the anti-cylinder pulling performance of an internal combustion engine cylinder liner disclosed in CN117307347A is to improve the lubrication performance of the cylinder bore surface by spraying a coating on the cylinder bore, thereby improving the cylinder pulling performance; a new type of anti-cylinder pulling piston ring disclosed in CN205225486U improves the cylinder pulling problem by spraying a coating on the piston ring; it can be seen that they both improve the cylinder pulling problem by improving the friction performance of the cylinder bore-piston ring group, and the core is to optimize the lubrication performance of the cylinder bore. To improve the deformation of the cylinder bore by optimizing the lubrication, it must be based on the stiffness strength of the cylinder bore itself to meet certain design requirements. In the case of insufficient strength of the cylinder material or lack of structural design stiffness, improving the lubrication performance may not achieve the effect of overcoming the cylinder pulling.

[0009] In summary, existing technical solutions tend to be empirical designs, and solving problems mainly relies on the designer's own experience and multiple trials and errors to achieve the goal. This is inefficient and sometimes difficult to achieve results when faced with coupled factors. Summary of the invention

[0010] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a cylinder structure design method for a diesel engine anti-pull cylinder based on CAE technology, which can effectively avoid design defects and reduce the risk of diesel engine cylinder pull caused by improper design.

[0011] The technical solution of the present invention is:

[0012] A cylinder body structure design method of a diesel engine anti-pull cylinder based on CAE technology, wherein the diesel engine cylinder body mainly includes a cylinder hole, a cooling water jacket, bolt thread fasteners, a lubrication system and other structures, and the cylinder body structure design method of the diesel engine anti-pull cylinder includes:

[0013] Step 1: Based on the prototype and 3D model of the diesel engine cylinder block, modal tests and modal finite element simulation calculations are performed on the diesel engine cylinder block. According to the calculation results, reinforcing ribs are added to the structures such as the cylinder main bearing seat, cylinder head and skirt side wall symmetrically distributed around the center of the cylinder hole, so as to balance the deformation of both sides of the diesel engine cylinder block under vibration excitation, improve dynamic stiffness and reduce cylinder hole deformation;

[0014] Step 2: Based on the three-dimensional model of the diesel engine cylinder block and cylinder head, extract the three-dimensional model of the cooling water jacket, and perform coupled calculation on the temperature field of the diesel engine cylinder block and cylinder head and the fluid flow of the cooling water jacket, striving to increase the cooling and heat dissipation capacity of the cooling water jacket and reduce the thermal deformation of the cylinder bore while ensuring the coolant distribution ratio of the cylinder block and cylinder head and the heat dissipation requirements of the intake and exhaust sides;

[0015] Step 3: Based on the three-dimensional model of the diesel engine cylinder block and cylinder head, a finite element calculation model of the diesel engine cylinder block including the cylinder block, cylinder head, cylinder gasket, and main bearing cap is constructed, and thermal-mechanical coupling calculation simulation is performed to evaluate the stress and deformation of key areas of the diesel engine cylinder block and optimize the axial force flow transmission of the cylinder block.

[0016] Furthermore, the step 1 further comprises:

[0017] Step 1.1: Based on the prototype and 3D model of the diesel engine cylinder block, perform finite element calculation preprocessing, use CAE meshing tools to mesh the entire diesel engine cylinder block area, and perform free mode and constrained mode calculation simulation;

[0018] Step 1.2: Based on the natural frequency values ​​and mode shape diagrams calculated by the modal, observe the mode shapes of the low-order modes;

[0019] Step 1.3: For the areas of the diesel engine cylinder block that are prone to deformation, set reinforcing ribs symmetrically distributed on the cylinder main bearing seat, cylinder head and skirt side wall with the center of the cylinder hole as the axis to balance the deformation of both sides of the diesel engine cylinder block under vibration excitation, improve dynamic stiffness and reduce cylinder hole deformation.

[0020] Furthermore, the step 2 further comprises:

[0021] Step 2.1: Based on the three-dimensional model of the diesel engine cylinder block and cylinder head, the CAE meshing tool is used to perform solid domain meshing, and boundary conditions such as material properties, wall temperature, and heat transfer coefficient are applied to calculate the cylinder temperature field;

[0022] Step 2.2: Extract the 3D model of the cooling water jacket, use the fluid flow meshing tool to mesh the fluid domain, apply boundary conditions such as initial temperature, heat transfer coefficient, pressure, flow rate, coolant properties, and perform CFD calculation of the cooling water jacket;

[0023] Step 2.3: Map the CFD calculation results of the cooling water jacket to the cylinder temperature field and perform fluid-solid coupling calculation;

[0024] Step 2.4: Based on the calculation results, determine the coolant flow rate and distribution ratio required for the cylinder block and cylinder head, and adjust the height of the cylinder block cooling water jacket in combination with the piston stroke and the position of each ring groove when the piston is at the bottom dead center; according to the height where the temperature in the cylinder bore is high and the gradient is large, drill an inclined water hole in the thin wall between the two cylinders to connect it to the cooling water jacket.

[0025] Step 2.5: Open an upper water hole on the top surface of the cylinder block that is connected to the cylinder head cooling water jacket. Based on the CFD calculation results, while ensuring the stiffness of the top surface of the cylinder block, comprehensively consider the coolant temperature difference between the cylinder block and the cylinder head and the required flow exchange to determine the shape and area of ​​the upper water hole; and balance the flow of coolant on the intake and exhaust sides by adjusting the bevel angle of the cooling water jacket inlet and the size of the upper water hole on the cylinder gasket according to the different heat dissipation requirements on the intake and exhaust sides of the cylinder block.

[0026] Furthermore, the step 3 further comprises:

[0027] Step 3.1: Based on the three-dimensional model of the diesel engine cylinder block and cylinder head, a finite element calculation model of the diesel engine cylinder block including the cylinder block, cylinder head, cylinder gasket, and main bearing cap is constructed to perform thermal-mechanical coupling calculation simulation;

[0028] Step 3.2: According to the radial and axial deformation of the cylinder bore under assembly conditions and hot engine conditions, adjust the position of the screwing surface of the cylinder head bolts and the cylinder body threads, lengthen the bolts appropriately, sink the screwing surface, and stagger the screwing surface with the cylinder body cooling water jacket; or extend the cylinder head bolts directly to the cylinder body skirt and fix them with nuts; or connect the cylinder head bolt bracket with the main bearing bolt bracket, and use through bolts to connect the cylinder head, cylinder body and main bearing cap.

[0029] Step 3.3: According to the deformation of the cylinder bore, a thin groove is opened in the thin wall between the two cylinders to connect the cooling water jackets to reduce the mutual interference caused by the deformation of the cylinder bores of the two cylinders.

[0030] Furthermore, the CAE software used for diesel engine cylinder block and cylinder head design analysis is ABAQUS and FAMFET.

[0031] Furthermore, the CAE software used for diesel engine cylinder block and cylinder head design analysis is ANSYS, NASTRAN, NCODE, and FESAFE.

[0032] The present invention also provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the cylinder body structure design method of the anti-pull cylinder of a small and medium-power diesel engine described in the present invention are implemented.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] Since the diesel engine cylinder block is the main component that bridges other components in the diesel engine, it is subject to high thermal and mechanical loads. In addition, the cylinder block contains flow channels for fluids such as cooling water, lubricating oil and air. The overall load situation is complex. It is difficult to meet the design requirements if only one of the factors is considered. The method of the present invention comprehensively considers the effects of the cooling water jacket, temperature field and force on the cylinder block, couples the three factors of "fluid-solid-heat", and systematically conducts simulation analysis to guide design and optimization. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention is a flowchart of a method for designing a cylinder structure of an anti-pull cylinder of a diesel engine according to an embodiment of the present invention.

[0036] Figure 2 Schematic diagram of the finite element model of the cylinder body and its accessories.

[0037] Figure 3 This is the vibration shape diagram of the modal test.

[0038] Figure 4 Calculates mode shape diagrams for modal finite elements.

[0039] Figure 5 Schematic diagram of the cylinder side reinforcement ribs.

[0040] Figure 6 This is a full view of the cooling water jacket of the cylinder block and cylinder head of this diesel engine.

[0041] Figure 7 This is a top view of the diesel engine cylinder cooling water jacket.

[0042] Figure 8 This is a cross-sectional view of the oblique water hole of this diesel engine.

[0043] Fig. 9 Several implementation methods for improving cylinder head bolts. DETAILED DESCRIPTION

[0044] The technical solution of the present invention is described in detail below with reference to the accompanying drawings.

[0045] See also Figure 1A cylinder body structure design method for a small and medium-power diesel engine anti-pull cylinder. The diesel engine cylinder body mainly includes a cylinder hole, a cooling water jacket, bolt thread fasteners, a lubrication system and other structures. The cylinder body structure design method for the diesel engine anti-pull cylinder includes:

[0046] Step 1: Based on the prototype and 3D model of the diesel engine cylinder block, modal tests and modal finite element simulation calculations are performed on the diesel engine cylinder block. According to the calculation results, reinforcement ribs are added to the cylinder block main bearing seat, cylinder block head, skirt side wall and other structures symmetrically distributed around the center of the cylinder hole, so as to balance the deformation of both sides of the diesel engine cylinder block under vibration excitation, improve dynamic stiffness, and reduce cylinder hole deformation; specifically including:

[0047] Step 1.1: Based on the prototype and 3D model of the diesel engine cylinder block, perform finite element calculation preprocessing, use CAE meshing tools to mesh the entire diesel engine cylinder block area, and perform free mode and constrained mode calculation simulation;

[0048] Step 1.2: Based on the natural frequency values ​​and mode shape diagrams calculated by the modal, observe the mode shapes of the low-order modes;

[0049] Step 1.3: For the areas of the diesel engine cylinder block that are prone to deformation, set reinforcing ribs symmetrically distributed on the cylinder main bearing seat, cylinder head and skirt side wall with the center of the cylinder hole as the axis to balance the deformation of both sides of the diesel engine cylinder block under vibration excitation, improve dynamic stiffness and reduce cylinder hole deformation.

[0050] Step 2: Based on the three-dimensional model of the diesel engine cylinder block and cylinder head, extract the three-dimensional model of the cooling water jacket, and perform coupled calculation on the temperature field of the diesel engine cylinder block and cylinder head and the fluid flow of the cooling water jacket, so as to increase the cooling and heat dissipation capacity of the cooling water jacket and reduce the thermal deformation of the cylinder bore while ensuring the coolant distribution ratio of the cylinder block and cylinder head and the heat dissipation requirements of the intake and exhaust sides; specifically including:

[0051] Step 2.1: Based on the three-dimensional model of the diesel engine cylinder block and cylinder head, the CAE meshing tool is used to perform solid domain meshing, and boundary conditions such as material properties, wall temperature, and heat transfer coefficient are applied to calculate the cylinder temperature field;

[0052] Step 2.2: Extract the 3D model of the cooling water jacket, use the fluid flow meshing tool to mesh the fluid domain, apply boundary conditions such as initial temperature, heat transfer coefficient, pressure, flow rate, coolant properties, and perform CFD calculation of the cooling water jacket;

[0053] Step 2.3: Map the CFD calculation results of the cooling water jacket to the cylinder temperature field and perform fluid-solid coupling calculation;

[0054] Step 2.4: Based on the calculation results, determine the coolant flow rate and distribution ratio required for the cylinder block and cylinder head, and adjust the height of the cylinder block cooling water jacket in combination with the piston stroke and the position of each ring groove when the piston is at the bottom dead center; according to the height where the temperature in the cylinder bore is high and the gradient is large, drill an inclined water hole in the thin wall between the two cylinders to connect it to the cooling water jacket.

[0055] Step 2.5: Open an upper water hole on the top surface of the cylinder block that is connected to the cylinder head cooling water jacket. Based on the CFD calculation results, while ensuring the stiffness of the top surface of the cylinder block, comprehensively consider the coolant temperature difference between the cylinder block and the cylinder head and the required flow exchange to determine the shape and area of ​​the upper water hole; and balance the flow of coolant on the intake and exhaust sides by adjusting the bevel angle of the cooling water jacket inlet and the size of the upper water hole on the cylinder gasket according to the different heat dissipation requirements on the intake and exhaust sides of the cylinder block.

[0056] Step 3: Based on the three-dimensional model of the diesel engine cylinder block and cylinder head, a finite element calculation model of the diesel engine cylinder block including the cylinder block, cylinder head, cylinder gasket, and main bearing cap is constructed to perform thermal-engine coupling calculation simulation, evaluate the stress and deformation of each key area of ​​the diesel engine cylinder block, and optimize the axial force flow transmission of the cylinder block; specifically, it includes:

[0057] Step 3.1: Based on the three-dimensional model of the diesel engine cylinder block and cylinder head, a finite element calculation model of the diesel engine cylinder block including the cylinder block, cylinder head, cylinder gasket, and main bearing cap is constructed to perform thermal-mechanical coupling calculation simulation;

[0058] Step 3.2: According to the radial and axial deformation of the cylinder bore under assembly conditions and hot engine conditions, adjust the position of the screwing surface of the cylinder head bolts and the cylinder body threads, lengthen the bolts appropriately, sink the screwing surface, and stagger the screwing surface with the cylinder body cooling water jacket; or extend the cylinder head bolts directly to the cylinder body skirt and fix them with nuts; or connect the cylinder head bolt bracket with the main bearing bolt bracket, and use through bolts to connect the cylinder head, cylinder body and main bearing cap.

[0059] Step 3.3: According to the deformation of the cylinder bore, a thin groove is opened in the thin wall between the two cylinders to connect the cooling water jackets to reduce the mutual interference caused by the deformation of the cylinder bores of the two cylinders.

[0060] The CAE software used for the diesel engine cylinder block and cylinder head design analysis is ABAQUS and FAMFET.

[0061] The CAE software used for design and analysis of diesel engine cylinder block and cylinder head is ANSYS, NASTRAN, NCODE, and FESAFE.

[0062] Example 1

[0063] Step 1: Based on the prototype and 3D model of the diesel engine cylinder block, a modal test is performed on the diesel engine cylinder block, and modal finite element simulation calculation is performed using virtual prototype simulation software.

[0064] Figure 3 is the vibration shape diagram of the modal test; Figure 4 Calculate mode shape diagrams for modal finite elements;

[0065] It can be seen from the test and calculation results that the deformation of the cylinder block under vibration excitation occurs in the area of ​​the crankcase skirt close to the engine foot and in the overhanging structure near the cylinder head.

[0066] In order to improve the deformation of the crankcase skirt, reinforcing ribs are arranged on the side wall of the skirt and the main bearing seat, symmetrically with the center of the cylinder hole as the axis, such as Figure 5 As shown in the figure, symmetrical ribs are arranged on each main bearing seat and diverge from the center to support the main bearing seat, the crankcase skirt, and the cylinder head; on the main bearing seat at the front end of the cylinder body, due to the design requirements of the lubricating oil channel, there is a protruding oil channel from left to right, which also plays the role of a rib. In order to balance the left and right forces, a symmetrical rib from right to left is arranged; as shown in the figure Figure 5 As shown, symmetrical transverse and vertical reinforcement ribs are set on the two side walls of the cylinder body; in the machine foot area near the front end, from the modal vibration diagram, the deformation on the right side is obviously greater than that on the left side, so X-shaped cross reinforcement ribs are set on the left side to balance the deformation of the bottom of the two cylinder bodies.

[0067] Step 2: Based on the three-dimensional model of the diesel engine cylinder block and cylinder head, extract the three-dimensional model of the cooling water jacket, and use CFD simulation software to calculate the fluid flow of the cooling water jacket.

[0068] Figure 6 This is the overall view of the cooling water jacket of the cylinder block and cylinder head of this diesel engine. Figure 7 This is a top view of the diesel engine cylinder cooling water jacket. Figure 8 This is a cross-sectional view of the oblique water hole of this diesel engine.

[0069] According to the calculation of the cylinder head temperature field, it can be seen that the cylinder head temperature is higher than the cylinder block temperature, especially the area near the cylinder head exhaust. Therefore, the flow and flow rate requirements of the cylinder head cooling water jacket are greater than those of the cylinder block cooling water jacket. At the same time, in order to prevent the coolant of the cylinder block and cylinder head from having too large a temperature difference at the outlet, resulting in poor flow, the flow distribution ratio of the cylinder head and cylinder block is determined to be 1.6:1 according to the CFD calculation of the cooling water jacket.

[0070] It can be seen from the temperature field calculation results that the area with higher temperature and larger gradient is in the thin-walled area between the two cylinders. The height extends approximately from the cylinder top to the height of the second ring of the piston when it is at the top dead center, so the height of the cylinder cooling water jacket is determined by this; the temperature of the thin wall between the two cylinders of the cylinder block of this diesel engine is relatively high and it is not convenient to set up a cooling water jacket due to structural limitations, so cross-slanted water holes are set in the thin wall and processed by drilling in the fine processing stage. The height of the lower end of the inclined water hole is determined according to the position where the temperature gradient slows down.

[0071] At the water inlet of the cylinder cooling water jacket, the bevel direction of the water inlet is adjusted according to the heat exchange requirements of the inlet and exhaust sides of the water jacket. The heat exchange demand on the exhaust side is large, so the coolant flow rate and flow velocity on the exhaust side are increased to make the temperature performance of the inlet and exhaust sides in the fluid-solid coupling temperature field as close as possible to prevent cylinder bore deformation caused by excessive temperature difference on both sides.

[0072] Step 3: Based on the three-dimensional model of the diesel engine cylinder block and cylinder head, build a finite element calculation model of the diesel engine cylinder block including the cylinder block, cylinder head, cylinder gasket, and main bearing cover, and perform thermal-mechanical coupling calculation simulation.

[0073] According to the calculation results, the values ​​of the radial deformation of the cylinder bore at different heights under cold assembly conditions and hot engine conditions are extracted. With the help of Fourier transform, the influence of factors such as bolt preload, cooling water jacket height, water holes on the water jacket, and lateral force on the cylinder bore deformation is obtained to determine the optimization direction.

[0074] For this type of diesel engine cylinder block, in order to maximize the cooling and heat transfer capacity of the cylinder block and balance the coolant temperature of the cylinder block and cylinder head, the flow area of ​​the cylinder block water hole is expanded as much as possible within the allowable range of cylinder hole deformation, and supports are set in the lateral force and its opposite direction, front and rear ends, and on the bolt-cylinder center connection line, and all other places are opened as water holes.

[0075] According to the calculation results of cylinder bore deformation, the deformation of the cylinder bore of this diesel engine cylinder block is located at the upper part of the bolt thread engagement surface and the lower part of the cooling water jacket. There is an area that overlaps along the cylinder centerline. Since it contains both the cooling water jacket and the bolt hole structure, the stiffness of this area is poor and the cylinder bore deformation is large. Fig. 9 As shown, adjust the position of the screwing surface between the cylinder head bolts and the cylinder body threads, lengthen the bolts appropriately, sink the screwing surface, and stagger the screwing surface with the cylinder body cooling water jacket; or extend the cylinder head bolts directly to the cylinder body skirt and fix them with nuts; or connect the cylinder head bolt bracket with the main bearing bolt bracket, and use through bolts to connect the cylinder head, cylinder body and main bearing cap.

Claims

1. A method for designing the cylinder structure of a tension-resistant cylinder of a small and medium-power diesel engine, wherein the cylinder comprises a cylinder bore, a cooling water jacket, bolt thread fasteners and a lubrication system, characterized in that: The method comprises the following steps: Step 1: Based on the prototype and three-dimensional model of the diesel engine cylinder block, a modal test and a modal finite element simulation calculation are performed on the diesel engine cylinder block. According to the calculation results, reinforcing ribs are added with the center of the cylinder hole as the axis and symmetrically distributed on the main bearing seat, the cylinder head and the side wall of the skirt of the cylinder block to balance the deformation of both sides of the diesel engine cylinder block under vibration excitation, improve dynamic stiffness, and reduce deformation of the cylinder hole; Step 2: Based on the three-dimensional model of the diesel engine cylinder block and cylinder head, extract the three-dimensional model of the cooling water jacket, perform coupled calculation on the temperature field of the diesel engine cylinder block and cylinder head and the fluid flow of the cooling water jacket, and increase the cooling and heat dissipation capacity of the cooling water jacket and reduce the thermal deformation of the cylinder bore while ensuring the coolant distribution ratio of the cylinder block and cylinder head and the heat dissipation requirements of the intake and exhaust sides. Step 3: Based on the three-dimensional model of the diesel engine cylinder block and cylinder head, a finite element calculation model of the diesel engine cylinder block including the cylinder block, cylinder head, cylinder gasket, and main bearing cap is constructed to perform thermal-mechanical coupling calculation simulation to evaluate the stress and deformation of key areas of the diesel engine cylinder block and optimize the axial force flow transmission of the cylinder block.

2. The method according to claim 1, characterized in that: The step 1 further comprises: The CAE meshing tool is used to mesh the entire diesel engine cylinder block area, and the free mode and constrained mode calculation simulation is performed; Based on the natural frequency values ​​and mode shape diagrams calculated from the modal calculation, the mode shapes of the low-order modes are observed.

3. The method according to claim 1, characterized in that The step 2 further comprises: CAE meshing tools are used to mesh the solid domain, and material properties, wall temperature, and heat transfer coefficient boundary conditions are applied to calculate the cylinder temperature field. The fluid flow meshing tool is used to mesh the fluid domain, and the initial temperature, heat transfer coefficient, pressure, flow rate, and coolant property boundary conditions are applied to perform CFD calculations on the cooling water jacket.

4. The method according to claim 3, characterized in that The step 2 further comprises: The CFD calculation results of the cooling water jacket are mapped to the cylinder temperature field to perform fluid-solid coupling calculations.

5. The method according to claim 4, characterized in that The step 2 further comprises: Based on the calculation results, the coolant flow and distribution ratio required by the cylinder block and cylinder head are determined, and the height of the cylinder block cooling water jacket is adjusted in combination with the piston stroke and the position of each ring groove when the piston is at the bottom dead center; according to the height where the temperature in the cylinder bore is high and the gradient is large, an inclined water hole is drilled in the thin wall between the two cylinders to connect with the cooling water jacket.

6. The method according to claim 5, characterized in that The step 2 further comprises: An upper water hole connected to the cylinder head cooling water jacket is opened on the top surface of the cylinder block. Based on the CFD calculation results, the shape and area of ​​the upper water hole are determined by comprehensively considering the coolant temperature difference between the cylinder block and the cylinder head and the required flow exchange while ensuring the rigidity of the cylinder block top surface; and according to the different heat dissipation requirements on the intake and exhaust sides of the cylinder block, the flow of coolant on the intake and exhaust sides is balanced by adjusting the bevel angle of the cooling water jacket inlet and the size of the upper water hole on the cylinder gasket.

7. The method according to claim 1, characterized in that The step 3 further comprises: According to the radial and axial deformation of the cylinder bore under assembly conditions and hot engine conditions, adjust the position of the screwing surface between the cylinder head bolts and the cylinder body threads, lengthen the bolts appropriately, and sink the screwing surface so that the screwing surface is staggered with the cylinder body cooling water jacket; or extend the cylinder head bolts directly to the cylinder body skirt and fix them with nuts; or connect the cylinder head bolt bracket with the main bearing bolt bracket, and use through bolts to connect the cylinder head, cylinder body and main bearing cap.

8. The method according to claim 7, characterized in that The step 3 further comprises: According to the deformation of the cylinder bore, a fine groove is opened in the thin wall between the two cylinders to connect the cooling water jacket and reduce the mutual interference caused by the deformation of the cylinder bores of the two cylinders.

9. The method according to any one of claims 1 to 8, characterized in that: The CAE software for diesel engine cylinder block and cylinder head design analysis is ABAQUS or FAMFET; The CAE software used for diesel engine cylinder block and cylinder head design and analysis is ANSYS, NASTRAN, NCODE or FESAFE.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the cylinder structure design method of the anti-pull cylinder of a small and medium-power diesel engine as described in any one of claims 1 to 9 are implemented.

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