Cylinder cover heat transfer performance optimization method based on joint simulation technology

Abstract

The invention discloses a cylinder cover heat transfer performance optimization method based on a joint simulation technology, and belongs to the field of cylinder covers for energy and power engineering and internal combustion engines. The implementation method comprises the steps that a cylinder cover geometric model is built based on a parametric modeling method, and the structural shape of the cylinder cover geometric model is controlled through a cylinder cover expression; finite element mesh generation is conducted on the cylinder cover model based on an automatic mesh generation method, precise recognition of a fluid-solid coupling surface in the automatic calculation process of the heat transfer and exchange performance of the cylinder cover is achieved by combining a cylinder cover mesh and a cooling flow channel mesh, and a low-quality mesh is repaired based on a mesh node moving algorithm; a solver is driven by a macro command to conduct automatic simulation analysis on heat transfer and exchange performance of a steady-state flow field and a temperature field in the air cylinder cover, and temperature distribution of all positions on the air cylinder cover is obtained; and based on the constructed subjective and objective comprehensive evaluation function, selecting a group of samples with the highest score as an optimization result, and obtaining an optimal cylinder cover structure optimization result in a sample space.

Description

Technical Field

[0001] The present invention relates to a cylinder head optimization method, and in particular to a method for optimizing cylinder head parameters based on UG, ICEM, fluent and Isight software joint simulation technology, which is suitable for optimizing the heat transfer performance and lightweight degree of a cylinder head model, and belongs to the field of energy and power engineering, and cylinder heads for internal combustion engines. Background Art

[0002] The cylinder head is one of the key components of a diesel engine. It seals the top of the cylinder and forms a combustion chamber space together with the top of the piston and the side wall of the cylinder. When the diesel engine is running, the high-temperature gas generated by the combustion of diesel repeatedly impacts the cylinder head, which can easily cause the local temperature of the cylinder head to exceed the tolerance of the cylinder head material. Therefore, how to reasonably reduce the maximum temperature of the cylinder head by designing the cooling flow channel of the cylinder head has always been one of the difficult problems in the development of diesel engines. With the increase of engine power density, the thermal load on the fire surface of the cylinder head will become stronger and stronger, and the design of the cylinder head will become more and more challenging. Designers need to reduce the use of materials as much as possible to reduce the weight of the cylinder head while avoiding interference between the flow channel design of the cylinder head and other topological features, so as to achieve the design goal of lightweighting the whole machine. At the same time, it is also necessary to ensure that the minimum wall thickness of each part of the cylinder head meets the actual constraints of the casting process to prevent the thin-walled features from melting through and other types of damage failure during the casting process.

[0003] In the traditional process, the optimization of the heat transfer performance of the cylinder head mainly relies on simulation to determine the maximum temperature and convective heat transfer performance of the cylinder head corresponding to a certain structural scheme, and then analyzes the data and adjusts the structure in combination with design experience to achieve the design indicators of the cylinder head. For example, the optimization method given in the mature cylinder head thermal-mechanical coupling simulation analysis and optimization technology [1] (see Zhang Min, Zhang Yi, Zhang Qinxiu. Cylinder head structure optimization design based on thermal-mechanical coupling [J]. Combined Machine Tool and Automation Processing Technology, 2017, (6): 126-129.) is based on the orthogonal experimental design method to design multiple groups of experiments, and then manually calculate the structural parameter values ​​corresponding to each experiment to obtain the final required performance data. When there are fewer parameters involved and the level of change of each parameter is small, the workload and calculation time are not much, but as the difficulty of optimization design increases, such as when it may be necessary to adjust dozens of dimensions that are difficult to determine their primary and secondary order at the same time, the total number of experiments created by this method will increase exponentially, and the workload and calculation time will also increase exponentially. At this point, manually editing calculation tasks and performing trial calculations using traditional methods can no longer meet the large-scale data collection needs. It is necessary to study more efficient data collection methods to efficiently fill the complex sample space.

[0004] In response to the need to establish highly automated calculation processes, a variety of parameter optimization software such as Isight have emerged. Isight has already appeared in many other simple structure optimization fields. For example, the optimization process demonstrated in the prior art [2] (Fan Jiang, Zeng Weiwei, Wang Rongqiao, Shen Xiuli, Chen Zhiying. Optimization design of turbine blade shroud based on iSIGHT [J]. Journal of Aerospace Power, 2011, Vol. 26 (4): 745-751.) has demonstrated the technology of using Isight software to build an automated optimization process for models with relatively regular surfaces and simple geometric expressions such as turbine blades. However, at present, there are not many cases of applying this technology in the optimization of cylinder head heat transfer performance. The cylinder head design is different from the design of these geometrically simple parts in the following ways: (1) The cylinder head has a more complex geometry, with multiple structural dimensions affecting each other. It is more difficult to establish its parametric model and it is difficult to obtain a reasonable range of parameter changes. (2) The cylinder head will continuously generate new models as its structural parameters change. Therefore, before each round of simulation analysis, the finite element mesh of the cylinder head model and the cylinder head cooling channel model needs to be redrawn. This process is more difficult than the optimization of simple models and is more likely to generate low-quality meshes, affecting the accuracy and convergence of the calculation. (3) In each round of simulation analysis, the thermal boundary conditions and thermal loads applied to the cylinder head surface need to be reassigned. Since the cylinder head mesh model used in each round of simulation analysis is constantly changing, it is difficult to reassign the thermal boundary conditions using classic methods such as mesh number association or geometric voxel association. Summary of the invention

[0005] The purpose of the present invention is to provide a cylinder head heat transfer performance optimization method based on joint simulation technology, which realizes rapid update of cylinder head model based on data transmission between multiple modules, high-quality adaptive mesh drawing of cylinder head and automatic simulation analysis of steady-state flow field and temperature field inside cylinder head, and realizes heat transfer performance analysis of cylinder heads with various structures by repeatedly and automatically running the cylinder head heat transfer performance calculation process, forming a sample data set that characterizes the corresponding relationship between cylinder head structure and heat transfer performance, and selecting the optimal parameter value as the optimization result, so as to realize the optimization of cylinder head heat transfer performance based on joint simulation technology. The present invention can solve the problem that the traditional cylinder head heat transfer performance optimization method requires a lot of manual operation, and at the same time can ensure that the cylinder head has qualified mesh quality when automatically drawing the mesh, and screen out and remove the cylinder head model that does not converge in calculation, so as to improve the accuracy and efficiency of the cylinder head heat transfer performance optimization work.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] The present invention discloses a cylinder head heat transfer performance optimization method based on joint simulation technology. The cylinder head geometric model is constructed based on a parametric modeling method, and the structural shape of the cylinder head geometric model is controlled by using a cylinder head expression to realize rapid updating of the cylinder head geometric model; the cylinder head model is meshed by finite elements based on an automated meshing method, and the cylinder head mesh and the cooling channel mesh are drawn separately. The cylinder head mesh and the cooling channel mesh are merged to realize accurate identification of the fluid-solid coupling surface in the automatic calculation process of the cylinder head heat transfer performance, and low-quality meshes are repaired based on a mesh node movement algorithm to ensure that the cylinder head mesh model has a preset qualified mesh quality; simulation analysis is set based on the cylinder head heat transfer analysis method, and the macro command is used to drive the The solver performs automated simulation analysis of the steady-state flow field and temperature field inside the cylinder head, obtains the temperature distribution at each position on the cylinder head, and extracts key indicators that can reflect the heat transfer performance of the cylinder head; constructs a sample space based on the parameter variation range of the cylinder head geometric model, and repeatedly performs automated simulation analysis on each sample point independently. After screening out data with non-convergence and inaccuracy, a sample data set that characterizes the correspondence between the cylinder head structure and the heat transfer performance is obtained; establishes a comprehensive evaluation function, comprehensively considers multiple cylinder head heat transfer performance indicators to score the heat transfer performance of each sample point, and selects a group of samples with the best scores as the optimal cylinder head structure optimization result in the sample space, thereby realizing the optimization of the cylinder head heat transfer performance based on the joint simulation technology.

[0008] The present invention discloses a cylinder head heat transfer performance optimization method based on joint simulation technology, comprising the following steps:

[0009] Step 1: Parametrically model the cylinder head to obtain a cylinder head parametric model. The cylinder head cooling channel model is obtained through Boolean operations, and the cylinder head parametric model is associated with each identical parameter of the cylinder head cooling channel model. The initial value and upper and lower boundary values ​​of each parameter of the cylinder head parametric model are determined, and the cylinder head parametric model is gradually modified by "combining global parameter changes with modification error reporting features" until the cylinder head model meets the preset stability qualification requirements. The surfaces that need to be assigned different boundary conditions on the cylinder head parametric model and the cylinder head cooling channel model are classified, and the cylinder head parametric model and the cylinder head cooling channel model are saved in the form of surface features. By calling the API function of the UG software, the cylinder head parametric model and the cylinder head cooling channel model can be automatically updated with one click, thereby improving the update efficiency of the cylinder head parametric model and the cylinder head cooling channel model.

[0010] The specific implementation method of step one is:

[0011] S11: UG is selected as the modeling platform for parametric modeling of the cylinder head. The external features of the cylinder head are established by stretching or rotating the modeling method, and the features include the top plate, the bottom plate, and the side wall. The feature lines on the wall surfaces of the cylinder head intake and exhaust ducts are drawn by the modeling method of projection curves, and the surface features of the intake and exhaust ducts are connected by the modeling method of fitting surfaces to generate the surface features of the intake and exhaust ducts. The surface features constituting the intake and exhaust ducts are stitched to form entities, and the external features of the cylinder head are subtracted from the intake and exhaust duct entities by Boolean operations to obtain a cylinder head model that completes the airway modeling. The assembly features of the cylinder head are established by stretching, rotating, punching or rounding the modeling methods of the cylinder head that completes the airway modeling, and the features include fastening threaded holes, intake and exhaust pipe assembly holes, inlet and outlet assembly holes, injector assembly holes, and locating pin holes. The water inlet and outlet of the flow channel are drawn on the cylinder head with completed airway modeling by using the stretching modeling method. Starting from the water inlet, the flow channel geometry of the cylinder head is drawn by stretching, rotating, and stitching the surface at the position where the wall thickness on the cylinder head model is greater than the minimum wall thickness requirement of the process, until the flow channel geometry connects the water inlet and the water outlet, and the flow channel geometry is arranged at the position where the wall thickness is greater than the minimum wall thickness requirement of the process. When setting the size of the flow channel geometry, the minimum wall thickness requirement of the processing technology must be strictly met. Use Boolean operations to sum all the flow channel geometries to obtain the flow channel entity of the cylinder head model, and then use Boolean operations to subtract the cylinder head model with completed airway modeling and the flow channel entity of the cylinder head model to obtain the cylinder head model with completed airway and flow channel modeling. After the external features, airways, assembly features and runners of the cylinder head are modeled, weight-reducing geometries are established by stretching, rotating and stitching surfaces at locations on the top plate, bottom plate and side walls of the cylinder head that are not involved in assembly and sealing, and the size of the weight-reducing geometries is associated with the size of the runner geometries to always ensure that the minimum wall thickness on the cylinder head is greater than the minimum wall thickness requirement of the process. Boolean operations are used to subtract the cylinder head with completed assembly feature modeling from all weight-reducing geometries to obtain a cylinder head model that has completed parametric modeling.

[0012] S12: Obtain the cooling channel model of the cylinder head through Boolean operations. Delete the weight reduction features on the cylinder head parameterized model and save the model as copy 1; delete the weight reduction features and channel features on the cylinder head parameterized model and save the model as copy 2. Subtract the copy 1 model from the copy 2 model through Boolean operations to obtain the cooling channel model of the cylinder head. In the expression of the cylinder head cooling channel model, the parameters with the same meaning in copy 1 and copy 2 are associated, and the parameters include parameters for controlling external features and parameters for controlling air channel features, so that the parameters with the same meaning in the two sets of expressions always remain equal during the model update process. After the cylinder head cooling channel model with the same parameters associated is updated, the external features and air channel features of copy 1 and copy 2 will be updated synchronously when the parameters are updated, ensuring that the final entity obtained each time the cylinder head cooling channel model is updated is only the flow channel part of the cylinder head.

[0013] S13: Set parameter initial values ​​and parameter boundary values ​​for structural parameters on the cylinder head parametric model and the cylinder head cooling channel model. Set one of the parameter boundary values ​​of the cylinder head parametric model to the limit parameter when the wall thickness at each position of the cylinder head is the minimum wall thickness requirement of the process, and set the other to other limit dimensions that meet the cylinder head design requirements. The cylinder head design requirements include that the hydraulic diameter at each location of the flow channel shall not be less than the limit dimension that causes flow obstruction, the narrowest part of the cylinder head surface shall not be less than one-third of the minimum wall thickness requirement of the process, and there shall be no interference between the cylinder head flow channel, air channel, assembly features, weight reduction features and external wall surface. Some cylinder head dimensions are the reference dimensions set when the cylinder head parametric model is modeled. The initial value of the reference dimension parameter is set to the initial value used when the cylinder head parametric model is modeled, and then its boundary value is equal to the reference value. These dimensions do not change when the model is updated. After determining the upper and lower boundary values ​​of parameter changes for parameters other than the reference dimensions, the initial values ​​of the parameters other than the reference dimensions shall be set to the median of the upper and lower boundary values ​​to reduce the probability of errors when updating the cylinder head parametric model.

[0014] S14: The cylinder head parametric model is gradually modified by the method of "combining global parameter changes with error feature modification". When the cylinder head parametric model selects parameter values ​​within the parameter variation range obtained in S13 and substitutes them into the expression to update the model, and the model update exceeds the preset number of times and still does not report an error, it is determined that the stability of the cylinder head parametric model meets the conditions required for optimization. The function of this step S14 is to repeatedly test whether the cylinder head parametric model reports an error under different parameter values, and modify the error feature to gradually improve the cylinder head parametric model. Name all parameters except the reference size in the cylinder head parametric model expression, configure the data interface between Excel and UG, and import the parameter names of the cylinder head except the reference size and their corresponding parameter variation range into an Excel table, insert a random number formula to randomly select a parameter value within the variation range for all parameters except the reference size, and then select all random parameter values ​​generated by the random number formula together with the names of all parameters except the reference size as the data source of the cylinder head parametric model, and use the Excel table to drive UG to update the model many times to test the parameter stability of the cylinder head parametric model under random parameter values. The parameter stability of the cylinder head parametric model is considered qualified when no error occurs when the cylinder head parametric model is updated for a preset number of consecutive times using random parameter values; if an error occurs, the error feature prompted in the UG software is modified or the dimensional variation range corresponding to the feature is modified until the cylinder head parametric model is updated for a preset number of consecutive times using random parameter values ​​without any error.

[0015] S15: Classify the surfaces on the cylinder head parameterized model and the cylinder head cooling channel model that need to be assigned different boundary conditions, and save the cylinder head parameterized model and the cylinder head cooling channel model in the form of surface features. When performing automatic calculation of the cylinder head heat transfer performance, boundary conditions can only be automatically assigned to surface features. Extracting the surfaces of the cylinder head parameterized model and the cylinder head cooling channel model as multiple surface features based on the type of boundary condition area can achieve the effect of automatically identifying the boundary condition area in the solver. Based on the cylinder head heat transfer analysis method, the surfaces on the cylinder head parameterized model and the cylinder head cooling channel model are classified, and the surface categories include water inlet, water outlet, channel wall, fluid-solid coupling surface, symmetry surface, outer wall, intake channel wall, exhaust channel wall and fire surface. Through the modeling method of extracting geometric features, these surfaces are extracted into surface features according to categories on the cylinder head parametric model and the cylinder head cooling channel model, and the original solid models in the cylinder head parametric model and the cylinder head cooling channel model are hidden. After the cylinder head parametric model and the cylinder head cooling channel model in the form of surface features are obtained, they are saved separately, and all surface features are set to be associated with the hidden cylinder head and cylinder head cooling channel entities.

[0016] S16: Automatically update the cylinder head model by calling the API function of UG. Call the API function of UG to read the cylinder head parameterized model path and the cylinder head cooling channel model path, read the cylinder head parameterized model expression path, automatically update the cylinder head parameterized model and the cylinder head cooling channel model using the expression parameter value, and save the cylinder head parameterized model and the cylinder head cooling channel model corresponding to the new parameter value, so as to realize the one-key automatic update of the cylinder head parameterized model and the cylinder head cooling channel model.

[0017] Step 2: Mesh the cylinder head parameterized model and the cylinder head cooling channel model respectively, and merge the surface mesh models of the cylinder head and the cylinder head cooling channel after meshing. Fix the mesh problem of the merged cylinder head surface mesh model, draw the cylinder head body mesh model, and improve the mesh quality of the cylinder head body mesh model. Set up the simulation based on the cylinder head heat transfer analysis method, and set the fluid-solid coupling surfaces of the cylinder head and the cylinder head cooling channel mesh models as coupling relationships, so as to solve the problem that the meshes on the fluid-solid coupling surfaces of the cylinder head and the cylinder head cooling channel mesh models do not share common nodes. Perform heat transfer performance analysis of the steady-state flow field and temperature field inside the cylinder head to obtain the temperature distribution at each position on the cylinder head. Perform mesh independence analysis of the cylinder head heat transfer performance calculation, and select a mesh size with a short calculation time and a calculation result with a deviation less than a preset threshold from the calculation result under other mesh sizes as the finite element mesh size used for optimization. The short calculation time refers to a calculation time shorter than the preset threshold.

[0018] The specific implementation method of step 2 is:

[0019] S21: Mesh the cylinder head parametric model and the cylinder head cooling channel model respectively. Use the minimum wall thickness requirement size as the initial mesh size for mesh drawing to ensure the mesh quality at the minimum position of the cylinder head wall. Import the cylinder head parametric model and the cylinder head cooling channel model into ICEM. Set the mesh size to the minimum wall thickness requirement size, and use the Patch Independent meshing method to divide the surface mesh to avoid mesh drawing failure caused by geometric shape distortion in some positions. The geometric shape distortion includes broken surfaces on the cylinder head parametric model and the cylinder head cooling channel model, narrow surfaces with a width less than the minimum wall thickness requirement of the process, or an angle between two surfaces less than 15°. Complete meshing of the cylinder head and the cylinder head cooling channel respectively, and output and save the surface mesh model of the cylinder head and the cylinder head cooling channel.

[0020] S22: Merge the surface mesh models of the cylinder head and the cylinder head cooling channel. When calculating the heat transfer performance of the cylinder head, the mesh models of the cylinder head and the cylinder head cooling channel need to set boundary conditions. After the meshes of the cylinder head and the cylinder head cooling channel are drawn, the mesh models of the cylinder head and the cylinder head cooling channel are merged and then calculated to achieve the simultaneous setting of the boundary conditions of the cylinder head and the cylinder head cooling channel. Import the surface mesh models of the cylinder head and the cylinder head cooling channel in ICEM, and merge the two meshes to obtain the merged cylinder head surface mesh model.

[0021] S23: Improve the mesh quality of the merged cylinder head surface mesh model. The surface mesh quality automatically drawn by ICEM is not high. If the volume mesh is directly drawn in ICEM and applied to the calculation, the calculation cannot converge. Importing the merged cylinder head surface mesh model into fluent meshing to repair the mesh problem and perform volume meshing can solve this problem and improve the mesh quality. In ICEM, the mesh areas in the merged cylinder head surface mesh model are named according to the water inlet, water outlet, flow channel wall, fluid-solid coupling surface, symmetry surface, outer wall, intake duct wall, exhaust duct wall and firepower surface. Import the merged cylinder head surface mesh model into fluent meshing, correct the three problems of free edge, self-intersection and repeated mesh, and reduce the mesh distortion to below the preset distortion. Draw the volume mesh model of the cylinder head based on the merged cylinder head surface mesh model, and repair the low-quality mesh based on the mesh node movement algorithm to reduce the inverse orthogonal quality to below the preset inverse orthogonal quality. Output the volume mesh model of the cylinder head.

[0022] S24: Set up simulation based on the cylinder head heat transfer analysis method, perform simulation analysis of the steady-state flow field and temperature field inside the cylinder head, and obtain the temperature distribution at each position on the cylinder head. Import the body mesh model of the cylinder head into fluent, set the scale of the simulation analysis, the calculation method used for the flow field calculation, and the material properties of the cylinder head and the coolant in the flow channel. Set the surface type of each surface on the cylinder head body mesh model, the surface includes the water inlet, water outlet, flow channel wall, fluid-solid coupling surface, symmetry surface, outer wall, intake channel wall, exhaust channel wall and fire surface, and the surface type includes inlet surface, outlet surface, wall surface and interface. Set the surface type of each fluid-solid coupling surface on the cylinder head and cylinder head cooling channel mesh model to the interface, and set the two fluid-solid coupling surfaces to a coupling relationship, so as to solve the problem that the meshes on the fluid-solid coupling surface of the cylinder head and cylinder head cooling channel mesh model do not share common nodes. Set the convection heat transfer coefficient and the initial wall temperature of the various surfaces. The monitoring and shutdown conditions are set for the calculation process and the simulation is initialized. The simulation calculation is submitted to obtain the temperature field simulation results of the cylinder head.

[0023] S25: Perform mesh independence analysis for calculating the heat transfer performance of the cylinder head. Starting from the initial value of the mesh size required by the minimum wall thickness of the process, expand or reduce the mesh size used when drawing the mesh model of the cylinder head and the cylinder head cooling channel surface, calculate the temperature field simulation results of the cylinder head at different mesh sizes, compare the effects of different mesh sizes on the calculation time and calculation results, select a mesh size with a short calculation time and a calculation result with a deviation less than a preset threshold value at other mesh sizes as the finite element mesh size used for optimization, and complete the mesh independence analysis, wherein the short calculation time refers to a calculation time shorter than the preset threshold value.

[0024] Step 3: Adjust the structural parameters of the cylinder head model to generate a cylinder head model with parameters different from the initial values. Record the scripts for the mesh model division and mesh merging of the cylinder head and cylinder head cooling channel surface in ICEM. Record the script for the mesh division of the cylinder head body in fluent meshing. Record the script for the calculation of the heat transfer performance of the cylinder head in fluent, and extract the index data that can characterize the heat transfer performance of the cylinder head and the quality of the cylinder head.

[0025] The specific implementation method of step three is:

[0026] S31: Adjust the structural parameters of the cylinder head model, automatically update the cylinder head model and the cylinder head cooling channel model, and generate a cylinder head model with parameters different from the initial values. Modify all parameters except the reference size in the expression of the cylinder head parametric model, call the UG API function, read the cylinder head parametric model expression, and automatically update the cylinder head parametric model and the cylinder head cooling channel model with one click.

[0027] S32: Record the scripts for the mesh model division and mesh merging of the cylinder head and cylinder head cooling channel. Based on the mesh size determined after mesh independence analysis, start script recording in ICEM, use the PatchIndependent meshing method to divide the surface mesh models of the cylinder head and cylinder head cooling channel, save the surface mesh models of the cylinder head and cylinder head cooling channel, and obtain the script for the surface mesh division. Start script recording in ICEM, import the surface mesh models of the cylinder head and cylinder head cooling channel, merge the two meshes, and name the mesh areas in the cylinder head surface mesh model according to the water inlet, water outlet, channel wall, fluid-solid coupling surface, symmetry surface, outer wall, intake duct wall, exhaust duct wall, and firepower surface. Obtain the merged cylinder head surface mesh model and the script for the mesh merging.

[0028] S33: Record the script for the cylinder head body meshing phase. Start the script recording in fluent meshing, import the merged cylinder head surface mesh model, correct the three problems of free edges, self-intersection and repeated meshes, and reduce the mesh distortion to below the preset distortion. Draw the cylinder head body mesh model, and repair the low-quality mesh based on the mesh node movement algorithm, and reduce the inverse orthogonal quality to below the preset inverse orthogonal quality. Output the cylinder head body mesh model and obtain the script for the body meshing phase.

[0029] S34: Record the script for calculating the heat transfer performance of the cylinder head. Start the script recording in Fluent, import the volume mesh model of the cylinder head, set the scale of the simulation analysis, the calculation method used for the flow field calculation, and the material properties of the cylinder head and the coolant in the flow channel. Set the surface type of each surface on the cylinder head volume mesh model, the surface includes the water inlet, water outlet, flow channel wall, fluid-solid coupling surface, symmetry surface, outer wall, intake channel wall, exhaust channel wall and fire surface, and the surface type includes inlet surface, outlet surface, wall surface and interface. Set the surface type of each fluid-solid coupling surface on the cylinder head and cylinder head cooling channel mesh model to the interface, and set the two fluid-solid coupling surfaces to the coupling relationship. Set the convective heat transfer coefficient and the initial wall temperature of the various surfaces. Set the monitoring and shutdown conditions for the calculation process and initialize the simulation, and submit the simulation calculation to obtain the temperature field simulation results of the cylinder head. Extract the index data that can characterize the heat transfer performance of the cylinder head and the quality of the cylinder head, including the surface average convection heat transfer coefficient, surface average pressure, surface average y+ value, surface minimum y+ value, surface maximum y+ value, body average water cavity temperature, body average cylinder head temperature, body average velocity, cylinder head total mass, cylinder head maximum temperature, water cavity maximum temperature, water cavity maximum velocity, water cavity minimum temperature and water cavity size. Output the cylinder head heat transfer performance calculation example and obtain the script of the cylinder head heat transfer performance calculation link.

[0030] Step 4: Build a cylinder head heat transfer performance optimization model based on joint simulation technology, use the Latin hypercube algorithm to plan the sample space for cylinder head heat transfer performance optimization, call the script recorded during the cylinder head heat transfer calculation process through batch commands, and automatically run the cylinder head parameterized model and cylinder head cooling channel model update, cylinder head mesh drawing, cylinder head heat transfer performance simulation analysis and cylinder head heat transfer performance index data extraction in the cylinder head heat transfer performance optimization test design process to obtain a sample data set that characterizes the corresponding relationship between cylinder head structure and heat transfer performance. Establish a comprehensive evaluation function, comprehensively consider multiple cylinder head heat transfer performance data to score each sample point, select the best scoring group of samples as the optimization result, and obtain the optimal cylinder head structure in the sample space, that is, to achieve cylinder head heat transfer performance optimization based on joint simulation technology.

[0031] The specific implementation method of step 4 is:

[0032] S41: Build a cylinder head heat transfer performance optimization model in Isight, set the total number of samples according to the computing power conditions, and use the Latin hypercube algorithm to plan the sample space when optimizing the cylinder head heat transfer performance, so that the sample points are evenly distributed in the high-dimensional Euclidean space to ensure the quality of the sample data. Call the script recorded during the cylinder head heat transfer calculation process through batch commands, and use different modules to execute the commands for updating the cylinder head model and the cylinder head cooling channel model, drawing the cylinder head mesh, calculating the cylinder head heat transfer performance, and extracting the heat transfer performance index data. After the settings are completed, the cylinder head heat transfer performance optimization model is automatically run to obtain a sample data set that characterizes the corresponding relationship between the cylinder head structure and the heat transfer performance.

[0033] S42: Establish a comprehensive evaluation function, comprehensively consider the fluctuation degree and importance of multiple cylinder head heat transfer performance indicators, and score the heat transfer performance of each sample point. As a preferred embodiment, the comprehensive evaluation function is shown in the following formula:

[0034]

[0035] Among them, g j is the comprehensive score of the jth evaluated sample point, λ i is the weight of the i-th evaluated indicator, y ij is the actual value of the i-th evaluated indicator of the j-th evaluated sample point, Z i is the ideal value of the i-th evaluated indicator of the evaluated sample point, σ i is the standard deviation of the i-th evaluated indicator data, and n is the total number of indicators evaluated at the sample point.

[0036] The weight of the i-th evaluated indicator can be calculated using the following formula:

[0037]

[0038] C i is the significance coefficient of the ith indicator, C i The larger the value is, the greater the impact of the i-th indicator on the comprehensive evaluation results, and the higher the weight is. i The standard deviation σ i and the correlation coefficient R i The product of is:

[0039] C i =σ i R i (3)

[0040] Standard deviation i Calculated using the following formula:

[0041]

[0042] In the formula, m is the total number of sample points used to calculate the standard deviation, x ij is the dimensionless data of the i-th performance index of the j-th sample point, is the dimensionless data average of the i-th performance indicator. The dimensionless data of the i-th performance indicator at the j-th sample point can be dimensionlessized by the following formula to obtain the data average:

[0043]

[0044] Correlation coefficient R i It can be calculated using the following formula:

[0045]

[0046] r ik is the linear correlation coefficient between the i-th indicator and the k-th indicator, which can be calculated using the following formula:

[0047]

[0048] After calculating all the above variables according to the sample data set, each sample point is scored through the comprehensive evaluation function, and the group of samples with the best scores are selected as the optimization results to obtain the optimal cylinder head structure in the sample space, that is, to achieve the optimization of the heat transfer performance of the cylinder head based on the joint simulation technology.

[0049] The process also includes step 5, performing process adaptability design according to the optimal cylinder head structure obtained in step 4, and obtaining a cylinder head design scheme that meets production constraints. The cylinder head manufactured by the cylinder head design scheme can improve the heat transfer performance, reduce the maximum temperature of the fire surface, reduce the thermal deformation effect, improve the heat transfer performance of the flow field and the stability of the flow characteristics, and the weight of the cylinder head after optimization is also lighter than that of the cylinder head before optimization, thereby achieving lightweight cylinder head.

[0050] Beneficial effects:

[0051] 1. The present invention discloses a method for optimizing the heat transfer performance of a cylinder head based on joint simulation technology. A parametric modeling method is used to build a parametric model of the cylinder head, and then a cooling channel model of the cylinder head is obtained by Boolean operations, thereby directly controlling the structural shape of the cylinder head and the cylinder head cooling channel through the expression of the cylinder head parametric model, thereby improving the efficiency of modifying and updating the cylinder head model and the cylinder head cooling channel model.

[0052] 2. The present invention discloses a cylinder head heat transfer performance optimization method based on joint simulation technology, which determines the initial value and upper and lower boundary values ​​of each parameter of the cylinder head parameterized model, and gradually modifies the cylinder head parameterized model by "combining global parameter changes with modification error reporting features", thereby ensuring that the cylinder head model has sufficient stability and achieving the effect that any value of the cylinder head parameterized model expression within the parameter variation range can stably update the cylinder head parameterized model and the cylinder head cooling channel model.

[0053] 3. The present invention discloses a cylinder head heat transfer performance optimization method based on joint simulation technology. By calling the API function of UG software, the cylinder head parameterized model and the cylinder head cooling channel model are automatically updated with one key, which omits the steps of opening the UG graphical window and then modifying the cylinder head parameterized model and the cylinder head cooling channel model, thereby improving the update efficiency of the cylinder head parameterized model and the cylinder head cooling channel model and meeting the necessary conditions for automating the cylinder head heat transfer calculation process.

[0054] 4. The present invention discloses a method for optimizing the heat transfer performance of a cylinder head based on joint simulation technology, which performs surface mesh division on the cylinder head and the cylinder head cooling channel respectively, merges the surface mesh models of the cylinder head and the cylinder head cooling channel and draws a cylinder head body mesh model, and then associates the coupling surfaces of the cylinder head and the cylinder head cooling channel with each other in the cylinder head body mesh model, thereby realizing the successful calculation of the coupling surfaces of the cylinder head and the cylinder head cooling channel under the premise that the meshes do not share common nodes.

[0055] 5. The present invention discloses a cylinder head heat transfer performance optimization method based on joint simulation technology, which completes the preliminary trial calculation of the cylinder head heat transfer performance under the grid size required by the process minimum wall thickness and performs grid independence analysis of the cylinder head heat transfer performance calculation, and selects a grid size with short calculation time and small deviation between the calculation result and the calculation result under other grid sizes as the finite element grid size used in optimization, thereby ensuring the accuracy of the cylinder head optimization result and saving the time cost of the cylinder head heat transfer optimization link to the greatest extent.

[0056] 6. The present invention discloses a method for optimizing the heat transfer performance of a cylinder head based on joint simulation technology. By recording the scripts of the mesh model division and mesh merging of the cylinder head and the cylinder head cooling channel surface in ICEM, recording the script of the mesh division of the cylinder head body in fluent meshing, and recording the script of the cylinder head heat transfer performance calculation and the extraction of index data of the cylinder head heat transfer performance in fluent, the accurate reproduction and automatic operation of the finite element mesh division work and the simulation analysis setting work in the process of calculating the heat transfer performance of the cylinder head can be achieved, thereby improving the efficiency of the heat transfer optimization of the cylinder head.

[0057] 7. The present invention discloses a cylinder head heat transfer performance optimization method based on joint simulation technology. The cylinder head heat transfer performance optimization model is built based on joint simulation technology. The Latin hypercube algorithm is used to plan the sample space when optimizing the cylinder head heat transfer performance. The total number of samples can be set according to the computing power conditions for experimental design. The sample points in the sample data used for cylinder head heat transfer optimization are sufficiently uniform, and the sample number and computing time cost are controllable.

[0058] 8. The present invention discloses a cylinder head heat transfer performance optimization method based on joint simulation technology. Based on the joint simulation technology, a cylinder head heat transfer performance optimization model is built. The script recorded during the cylinder head heat transfer calculation process is called through a batch command to automatically run the cylinder head model and cylinder head cooling channel model update, cylinder head mesh drawing, cylinder head heat transfer performance calculation and heat transfer performance index data extraction operations in the cylinder head heat transfer performance optimization test design process, so as to realize the automatic calculation of the effect of the sample point structure parameters in the sample space corresponding to the cylinder head heat transfer performance, thereby improving the efficiency of cylinder head optimization. During the calculation process, the model will automatically filter and remove sample points with unconvergent calculations and substandard mesh quality to ensure the quality of the sample data set.

[0059] 9. The present invention discloses a cylinder head heat transfer performance optimization method based on joint simulation technology, establishes a comprehensive evaluation function, considers multiple cylinder head heat transfer performance indicators to score the heat transfer performance of each sample point, realizes a comprehensive evaluation of the cylinder head heat transfer performance, ensures that the cylinder head heat transfer optimization result has the greatest improvement in comprehensive performance, and that each sub-indicator can be balanced. The cylinder head processed using the optimization result scheme selected by the comprehensive evaluation function has a longer service life and better heat transfer performance, and is effectively lightweight. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 It is a flow chart of a cylinder head heat transfer performance optimization method based on joint simulation technology of the present invention;

[0061] Figure 2 The surface feature cylinder head parameterized model and the cylinder head cooling channel model are respectively established in combination with the optimization method of the present invention, wherein: Figure 2 (a) is the parametric model of the cylinder head in the form of surface features. Figure 2 (b) The cylinder head cooling channel model in the form of surface features;

[0062] Figure 3 The cylinder head temperature field cloud map is obtained by using a 5mm grid size after the grid independence analysis in Example 1 obtains the optimal grid size of 5mm;

[0063] Figure 4It is the cylinder head surface mesh model, cylinder head cooling channel surface mesh model and merged cylinder head surface mesh model obtained after one-click automatic cylinder head surface mesh division, where: Figure 4 (a) is the mesh model of the cylinder head surface. Figure 4 (b) is the mesh model of the cylinder head cooling channel surface. Figure 4 (c) is the mesh model of the cylinder head surface after merging;

[0064] Figure 5 It is the cylinder head body mesh model obtained after one-click automatic cylinder head body mesh division.

[0065] Figure 6 This is a workflow diagram for building a cylinder head heat transfer performance optimization model in Isight.

[0066] Figure 7 It is the optimized cylinder head model structure. DETAILED DESCRIPTION

[0067] The invention is further described below with reference to the accompanying drawings and embodiments.

[0068] Embodiment 1:

[0069] like Figure 1 The figure shows a cylinder head heat transfer performance optimization method based on the joint simulation technology disclosed in this embodiment, and the specific implementation steps are as follows:

[0070] Step 1: Parametrically model the cylinder head to obtain a cylinder head parametric model. Obtain the cylinder head cooling channel model through Boolean operations, and associate the cylinder head parametric model with the same parameters of the cylinder head cooling channel model. Determine the initial value and upper and lower boundary values ​​of each parameter of the cylinder head parametric model, and gradually modify the cylinder head parametric model by "global parameter change + modify error reporting features" until its parameter stability is qualified. Classify the faces that need to be assigned different boundary conditions on the cylinder head parametric model and the cylinder head cooling channel model, and save the cylinder head parametric model and the cylinder head cooling channel model in the form of surface features. By calling the API function of the UG software, the cylinder head parametric model and the cylinder head cooling channel model can be automatically updated with one click, thereby improving the update efficiency of the cylinder head parametric model and the cylinder head cooling channel model.

[0071] The specific implementation method of step one includes the following steps:

[0072] Step 1.1: Use the stretching or rotation modeling method in UG to create the top plate, bottom plate and side wall of the cylinder head. Use projection curves to draw the feature lines on the cylinder head intake and exhaust duct walls, use fitting surfaces to generate the surface features of the intake and exhaust duct walls, stitch the surface features to form entities, and use Boolean operations to subtract the air duct from the cylinder head top plate, bottom plate and side wall to complete the intake and exhaust duct modeling. Use stretching, rotation, punching or rounding modeling methods to create the 22mm fastening threaded holes, 8.5mm intake and exhaust pipe assembly holes, 42mm injector assembly holes and 20mm locating pin holes of the cylinder head. The water inlet and outlet of the flow channel are drawn on the cylinder head by stretching modeling. Starting from the water inlet, 20 flow channel geometries of the cylinder head are drawn by stretching, rotating, and stitching surfaces at the position where the wall thickness of the cylinder head model is greater than 6mm, until the water inlet and the water outlet are connected and the flow channel is spread throughout the cylinder head. The flow channel geometries are summed by Boolean operation to obtain the flow channel entity of the cylinder head model. The cylinder head model with completed air channel modeling and the flow channel entity of the cylinder head model are subtracted by Boolean operation to obtain the cylinder head model with completed air channel and flow channel modeling; 6 weight reduction geometries are established by stretching, rotating, and stitching surfaces at the top plate, bottom plate, and side wall of the cylinder head where assembly and sealing are not involved, and the size of the weight reduction geometries is associated with the size of the flow channel geometries to always ensure that the minimum wall thickness on the cylinder head is greater than 6mm. The cylinder head with completed assembly feature modeling is subtracted by Boolean operation from all weight reduction geometries to obtain the cylinder head model with completed parametric modeling.

[0073] Step 1.2: Delete the weight reduction features on the cylinder head parameterized model and save the model as copy 1; delete the weight reduction features and flow channel features on the cylinder head parameterized model and save the model as copy 2. Subtract the copy 1 model from the copy 2 model by Boolean operation to obtain the cooling channel model of the cylinder head. In the expression of the cylinder head cooling channel model, the parameters with the same meaning in copy 1 and copy 2 are associated. In this embodiment, the parameters that need to be modified include the parameters that control the cylinder head shape and the parameters that control the air channel shape, a total of 53.

[0074] Step 1.3: Set the initial values ​​of the 96 reference dimension parameters constituting this embodiment as the initial values ​​used in the parametric modeling of the cylinder head, and then set their boundary values ​​equal to the reference values. These dimensions do not change when the model is updated. Among the 100 parameters other than the reference dimensions, this embodiment only optimizes the parameters controlling the flow channel shape. After determining the upper and lower boundary values ​​of the parameter changes for the 31 parameters controlling the flow channel shape, set the initial values ​​of the parameters of the 31 parameters controlling the flow channel shape to the median of the upper boundary value and the lower boundary value.

[0075] Step 1.4: Configure the data interface between Excel software and UG software, import the names of the 31 parameters that control the flow channel shape and their corresponding parameter variation ranges into the Excel table, insert a random number formula to randomly select a parameter value within the variation range for the 31 parameters that control the flow channel shape, and then select all the random parameter values ​​generated by the random number formula together with the names of the 31 parameters that control the flow channel shape as the data source of the cylinder head parametric model. Use the Excel table to drive UG to update the model to test the parameter stability of the cylinder head parametric model under random parameter values. The parameter stability of the cylinder head parametric model is considered qualified when no error occurs when the cylinder head parametric model is updated ten times in a row with random parameter values.

[0076] Step 1.5: Based on the cylinder head heat transfer analysis method, the surface feature areas of the water inlet, water outlet, channel wall, fluid-solid coupling surface, symmetry surface, outer wall, intake channel wall, exhaust channel wall and fire surface are selected on the cylinder head parametric model and cylinder head cooling channel model by extracting geometric features. All surface features are set to be associated with the hidden cylinder head and cylinder head cooling channel entities, and the original entity models in the cylinder head parametric model and cylinder head cooling channel model are hidden to obtain the cylinder head parametric model and cylinder head cooling channel model in the form of surface features. The final cylinder head parametric model in the form of surface features is as follows: Figure 2 As shown in a, the cylinder head cooling channel model in the form of surface features is as follows Figure 2 As shown in b.

[0077] Step 1.6: Call the UG API function to achieve one-key automatic update of the cylinder head parameterized model and the cylinder head cooling channel model in this embodiment.

[0078] Step 2: Mesh the cylinder head parameterized model and the cylinder head cooling channel model separately, and then merge the surface mesh models of the cylinder head and the cylinder head cooling channel. Fix the mesh problem of the merged cylinder head surface mesh model, draw the cylinder head body mesh model, and improve the mesh quality of the cylinder head body mesh model. Set up simulation analysis based on the cylinder head heat transfer analysis method, and set the fluid-solid coupling surfaces on the cylinder head and cylinder head cooling channel mesh models to a coupling relationship, so as to solve the problem that the meshes on the fluid-solid coupling surfaces of the cylinder head and cylinder head cooling channel mesh models do not share common nodes. Perform a simulation analysis of the heat transfer performance of the steady-state flow field and temperature field inside the cylinder head to obtain the temperature distribution at various locations on the cylinder head. Perform a mesh independence analysis of the cylinder head heat transfer performance calculation, and select a mesh size with a short calculation time and a small deviation from the calculation results under other mesh sizes as the finite element mesh size used for optimization.

[0079] The specific implementation method of step 2 includes the following steps:

[0080] Step 2.1: Use 6mm as the initial mesh size for mesh drawing. Import the cylinder head parametric model and the cylinder head cooling channel model into ICEM. Set the mesh size to 6mm, use the Patch Independent meshing method to divide the surface mesh, and output and save the surface mesh model of the cylinder head and the cylinder head cooling channel.

[0081] Step 2.2: Import the surface mesh models of the cylinder head and the cylinder head cooling channel into ICEM, and merge the two meshes to obtain the merged cylinder head surface mesh model.

[0082] Step 2.3: In ICEM, name the mesh areas in the merged cylinder head surface mesh model according to the water inlet, water outlet, flow channel wall, fluid-solid coupling surface, symmetry surface, outer wall, intake duct wall, exhaust duct wall and firepower surface. Import the merged cylinder head surface mesh model into fluent meshing, correct the three problems of free edges, self-intersection and repeated meshes, and reduce the mesh distortion to below 0.8. Draw the volume mesh model of the cylinder head based on the merged cylinder head surface mesh model, and repair the low-quality mesh based on the mesh node movement algorithm to reduce the inverse orthogonal quality to below 0.8. Output the volume mesh model of the cylinder head.

[0083] Step 2.4: Import the body mesh model of the cylinder head into Fluent, set the simulation analysis scale to 6mm, use the SIMPLE method for flow field calculation, use the ke model for turbulence calculation, and set the material properties of the cylinder head and the coolant in the flow channel to cast iron and water, respectively. Set the water inlet, water outlet, flow channel wall, fluid-solid coupling surface, symmetry surface, outer wall, intake channel wall, exhaust channel wall and fire surface of the cylinder head body mesh model to the inlet surface, outlet surface, wall surface and interface surface, respectively, according to the needs of simulation analysis. Set the surface type of the fluid-solid coupling surface on the cylinder head and cylinder head cooling channel mesh model to the interface, and set the two fluid-solid coupling surfaces to a coupling relationship. Set the ambient temperature of the fire surface to 812℃, the heat transfer coefficient to 1582W / (m2*K); the ambient temperature of the intake duct wall to 63℃, the heat transfer coefficient to 320W / (m2*K); the ambient temperature of the exhaust duct wall to 704℃, the heat transfer coefficient to 640W / (m2*K); the water inlet temperature to 25℃, and the water outlet temperature to 70℃. Set the shutdown condition to 200 simulation iterations and initialize the simulation, submit the simulation calculation to obtain the temperature field simulation results of the cylinder head.

[0084] Step 2.5: Starting from the initial value of the grid size of 6mm, expand or reduce the grid size used when drawing the grid model of the cylinder head and the cylinder head cooling channel surface, calculate the temperature field simulation results of the cylinder head at different grid sizes, compare the effects of different grid sizes on the calculation time and calculation results, and select a grid size with a short calculation time and a small deviation between the calculation results and the calculation results at other grid sizes as the finite element grid size used for optimization. After performing a grid independence analysis in this embodiment, a 5mm grid size was finally selected as the optimal grid size that takes into account both calculation speed and calculation accuracy, and the 5mm grid size was used in subsequent optimization. The cylinder head temperature field cloud map calculated with a 5mm grid size is shown below. Figure 3 shown.

[0085] Step 3: Adjust the structural parameters of the cylinder head model to generate a cylinder head model with parameters different from the initial values. Record the scripts for meshing the cylinder head and the cylinder head cooling channel surface and mesh merging in ICEM. Record the script for meshing the cylinder head body in fluent meshing. Record the script for calculating the heat transfer performance of the cylinder head in fluent and extract the index data that can characterize the heat transfer performance of the cylinder head.

[0086] The specific implementation method of step three includes the following steps:

[0087] Step 3.1: Adjust the structural parameters of the cylinder head model to generate a cylinder head model whose parameters are random numbers within a variation range.

[0088] Step 3.2: Start script recording in ICEM, and use the Patch Independent meshing method to divide the surface mesh models of the cylinder head and the cylinder head cooling channel with a mesh size of 5mm. Save the surface mesh models of the cylinder head and the cylinder head cooling channel and obtain the script for the surface mesh division link. Start script recording in ICEM, import the surface mesh models of the cylinder head and the cylinder head cooling channel one after another, merge the two meshes, and name the mesh areas in the cylinder head surface mesh model according to the water inlet, water outlet, channel wall, fluid-solid coupling surface, symmetry surface, outer wall, intake duct wall, exhaust duct wall and firepower surface to obtain the merged cylinder head surface mesh model and the script for the mesh merging link. The script can be used to realize one-click automatic division of the cylinder head surface mesh. The obtained cylinder head surface mesh model is as follows: Figure 4 The surface mesh model of the cylinder head cooling channel is shown in a. Figure 4 As shown in b, the merged cylinder head surface mesh model is as follows Figure 4 As shown in c.

[0089] Step 3.3: Start script recording in fluent meshing, import the merged cylinder head surface mesh model, correct the three problems of free edges, self-intersection and repeated meshes, and reduce the mesh distortion to below 0.8. Draw the volume mesh model of the cylinder head, and repair the low-quality mesh based on the mesh node movement algorithm, and reduce the inverse orthogonal quality to below 0.8. Output the volume mesh model of the cylinder head and obtain the script for the volume mesh division link. The script can be used to realize one-click automatic division of the cylinder head body mesh. The obtained cylinder head body mesh model is as follows Figure 5 shown.

[0090] Step 3.4: Start script recording in Fluent, import the volume mesh model of the cylinder head, set the simulation analysis scale to 5mm, use the SIMPLE method for flow field calculation, use the ke model for turbulence calculation, and set the material properties of the cylinder head and the coolant in the flow channel to cast iron and water, respectively. Set the water inlet, water outlet, flow channel wall, fluid-solid coupling surface, symmetry surface, outer wall, intake channel wall, exhaust channel wall and fire surface of the cylinder head volume mesh model to the inlet surface, outlet surface, wall surface and interface surface, respectively, according to the needs of simulation analysis. Set the surface type of the fluid-solid coupling surface on the cylinder head and cylinder head cooling channel mesh model to the interface, and set the two fluid-solid coupling surfaces to the coupling relationship. Set the ambient temperature of the fire surface to 812℃, and the heat transfer coefficient to 1582W / (m2*K); the ambient temperature of the intake duct wall to 63℃, and the heat transfer coefficient to 320W / (m2*K); the ambient temperature of the exhaust duct wall to 704℃, and the heat transfer coefficient to 640W / (m2*K); the water inlet temperature is 25℃, and the water outlet temperature is 70℃. Set the shutdown condition to 200 simulation iterations and initialize the simulation, submit the simulation calculation to obtain the temperature field simulation results of the cylinder head. Extract the surface average convection heat transfer coefficient, surface average pressure, surface average y+ value, surface minimum y+ value, surface maximum y+ value, body average water cavity temperature, body average cylinder head temperature, body average velocity, total mass of the cylinder head, maximum temperature of the cylinder head, maximum temperature in the water cavity, maximum velocity in the water cavity, minimum temperature in the water cavity, and water cavity size obtained by calculating the heat transfer performance of the cylinder head. Save the cylinder head heat transfer performance calculation example and obtain the script for the cylinder head heat transfer performance calculation link.

[0091] Step 4: Build a cylinder head heat transfer performance optimization model based on joint simulation technology, use the Latin hypercube algorithm to plan the sample space for cylinder head heat transfer performance optimization, call the script recorded during the cylinder head heat transfer calculation process through batch commands, and automatically run the cylinder head model and cylinder head cooling channel model update, cylinder head mesh drawing, cylinder head heat transfer performance calculation and heat transfer performance index data extraction in the cylinder head heat transfer performance optimization test design process to obtain a sample data set that characterizes the corresponding relationship between cylinder head structure and heat transfer performance. Establish a comprehensive evaluation function, comprehensively consider multiple cylinder head heat transfer performance indicators to score the heat transfer performance of each sample point, select the best scoring group of samples as the optimization result, and obtain the optimal cylinder head structure design scheme in the sample space.

[0092] The specific implementation method of step 4 includes the following steps:

[0093] Step 4.1: Build a cylinder head heat transfer performance optimization model in Isight. The workflow is available Figure 6 The flowchart is represented by . Based on the i5-10500CPU and 16GB memory computing device used, the total number of samples in the sample space is set to 500, and the Latin hypercube algorithm is selected to plan the sample space for optimizing the heat transfer performance of the cylinder head. The script recorded during the cylinder head heat transfer calculation process is called through batch commands, and different modules are used to execute the commands for updating the cylinder head model and the cylinder head cooling channel model, drawing the cylinder head mesh, calculating the cylinder head heat transfer performance, and extracting the heat transfer performance index data. After the settings are completed, the cylinder head heat transfer performance optimization model is automatically run, and after several rounds of calculations, a sample data set that characterizes the correspondence between the cylinder head structure and the heat transfer performance is obtained.

[0094] Step 4.2: Establish a comprehensive evaluation function, comprehensively consider the floating degree and importance of multiple cylinder head heat transfer performance indicators, and score the heat transfer performance of each sample point. In this embodiment, the cylinder head weight, maximum temperature and maximum flow rate in the cylinder head are selected as evaluation indicators, and the ideal value of each indicator is set to the minimum value of the indicator data. The weight of each indicator is calculated and scored using the comprehensive evaluation function. The group of samples with the best score is selected as the optimization result to complete the optimization of the cylinder head. The final optimized cylinder head model structure is as follows: Figure 7 shown.

[0095] The process also includes step 5, performing process adaptability design according to the optimization results obtained in step 4, and obtaining a cylinder head design scheme that meets actual production constraints. The cast iron cylinder head manufactured by this scheme is 10% lighter than the cylinder head before optimization, the maximum temperature is reduced from 520°C to 440°C, the vortex in the cylinder head flow channel is significantly reduced, and the maximum flow rate in the cylinder head is reduced from 17m / s to 11m / s. It can be seen that the optimized cylinder head has improved heat transfer performance and lightweight.

[0096] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A cylinder head heat transfer performance optimization method based on joint simulation technology, characterized in that: The cylinder head geometry model is constructed based on the parametric modeling method, and the cylinder head expression is used to control the structural shape of the cylinder head geometry model to achieve rapid update of the cylinder head geometry model; the cylinder head model is meshed by finite element based on the automated meshing method, and the cylinder head mesh and cooling channel mesh are drawn separately. The cylinder head mesh and cooling channel mesh are merged to achieve accurate identification of the fluid-solid coupling surface during the automatic calculation of the cylinder head heat transfer performance, and the low-quality mesh is repaired based on the mesh node movement algorithm to ensure that the cylinder head mesh model has the preset qualified mesh quality; simulation analysis is set based on the cylinder head heat transfer analysis method, and the macro command is used to drive the solver to perform automated simulation analysis of the steady-state flow field and temperature field inside the cylinder head, obtain the temperature distribution at each position on the cylinder head, and extract key indicators that can reflect the cylinder head heat transfer performance; A sample space is constructed based on the parameter variation range of the cylinder head geometric model, and automatic simulation analysis is repeatedly performed independently on each sample point. After screening out data with non-convergence and inaccuracy, a sample data set that characterizes the correspondence between the cylinder head structure and the heat transfer performance is obtained. A comprehensive evaluation function is established to score the heat transfer performance of each sample point by comprehensively considering multiple cylinder head heat transfer performance indicators, and the group of samples with the best scores are selected as the optimal cylinder head structure optimization results in the sample space, thereby realizing the optimization of the cylinder head heat transfer performance based on the joint simulation technology.

2. The method for optimizing the heat transfer performance of a cylinder head based on the joint simulation technology according to claim 1, characterized in that: The following steps are included: Step 1: parametrically model the cylinder head to obtain a cylinder head parametric model; obtain the cylinder head cooling channel model through Boolean operations, and associate the cylinder head parametric model with the same parameters of the cylinder head cooling channel model; determine the initial value and upper and lower boundary values ​​of each parameter of the cylinder head parametric model, and gradually modify the cylinder head parametric model by "combining global parameter changes with modification error reporting features" until the cylinder head parameters meet the preset stability qualification requirements; Classify the faces that need to be assigned different boundary conditions on the cylinder head parametric model and the cylinder head cooling channel model, and save the cylinder head parametric model and the cylinder head cooling channel model in the form of surface features; by calling the API function of the UG software, realize the one-click automatic update of the cylinder head parametric model and the cylinder head cooling channel model, and improve the update efficiency of the cylinder head parametric model and the cylinder head cooling channel model; Step 2: Mesh the cylinder head parameterized model and the cylinder head cooling channel model respectively, and merge the surface mesh models of the cylinder head and the cylinder head cooling channel after meshing; repair the mesh problem of the merged cylinder head surface mesh model, draw the cylinder head body mesh model, and improve the mesh quality of the cylinder head body mesh model; set up simulation analysis based on the cylinder head heat transfer analysis method, and set the respective fluid-solid coupling surfaces on the cylinder head and cylinder head cooling channel mesh models as coupling relationships; perform heat transfer performance simulation analysis of the steady-state flow field and temperature field inside the cylinder head to obtain the temperature distribution at various positions on the cylinder head; perform mesh independence analysis of the cylinder head heat transfer performance calculation, and select a mesh size with a short calculation time and a calculation result with a deviation less than a preset threshold from the calculation result under other mesh sizes as the finite element mesh size used for optimization; The short calculation time means that the calculation time is shorter than a preset threshold; Step 3: Adjust the structural parameters of the cylinder head model to generate a cylinder head model with parameters different from the initial values; record the scripts for mesh model division and mesh merging of the cylinder head and cylinder head cooling channel surface in ICEM; record the script for mesh division of the cylinder head body in fluent meshing; record the script for heat transfer performance calculation of the cylinder head in fluent, and extract the index data that can characterize the heat transfer performance of the cylinder head; Step 4: Build a cylinder head heat transfer performance optimization model based on joint simulation technology, use Latin hypercube algorithm to plan the sample space for cylinder head heat transfer performance optimization, call the script recorded during the cylinder head heat transfer calculation process through batch commands, and automatically run the cylinder head model and cylinder head cooling channel model update, cylinder head mesh drawing, cylinder head heat transfer performance calculation and heat transfer performance index data extraction in the cylinder head heat transfer performance optimization test design process to obtain a sample data set that characterizes the correspondence between cylinder head structure and heat transfer performance; establish a subjective and objective comprehensive evaluation function, comprehensively consider multiple cylinder head heat transfer performance indicators to score the heat transfer performance of each sample point, select the best scoring group of samples as the optimization result, and obtain the optimal cylinder head structure in the sample space, that is, to achieve cylinder head heat transfer performance optimization based on joint simulation technology.

3. The method for optimizing the heat transfer performance of a cylinder head based on the joint simulation technology according to claim 2, characterized in that: The method also includes step 5, performing process adaptability design according to the optimal cylinder head structure obtained in step 4 to obtain a cylinder head design scheme that meets production constraints; the cylinder head manufactured by the cylinder head design scheme can improve the heat transfer performance, reduce the maximum temperature of the fire surface, reduce the thermal deformation effect, improve the flow field heat transfer and stabilize the flow characteristics, and realize lightweight cylinder head compared with the cylinder head before optimization.

4. The method for optimizing the heat transfer performance of a cylinder head based on the joint simulation technology as claimed in claim 3, characterized in that: The specific implementation method of step one is: S11: Use UG as a modeling platform to perform parametric modeling of the cylinder head; use stretching or rotation modeling methods to establish the external features of the cylinder head, including the top plate, bottom plate, and side wall; use the projection curve modeling method to draw the characteristic lines on the wall surfaces of the cylinder head intake and exhaust ducts, use the fitting surface modeling method to connect the closed projection curves to generate the surface features of the intake and exhaust duct walls, sew the surface features that make up the intake and exhaust ducts to form a solid, and use Boolean operations to subtract the external features of the cylinder head from the intake and exhaust duct entities to obtain a cylinder head model that completes the airway modeling; use stretching, rotation, punching or rounding on the completed airway and modeled cylinder head model The assembly features of the cylinder head are established by the angle modeling method, and the features include fastening threaded holes, intake and exhaust pipe assembly holes, water inlet and outlet assembly holes, fuel injector assembly holes, and positioning pin holes; the water inlet and outlet of the flow channel are drawn on the cylinder head by the stretching modeling method, and the flow channel geometry of the cylinder head is drawn by stretching, rotating, and stitching surfaces at the position where the wall thickness of the cylinder head model after the airway modeling is completed is greater than the minimum wall thickness requirement of the process, until the flow channel geometry connects the water inlet and the water outlet, and the flow channel geometry is arranged at the position where the wall thickness is greater than the minimum wall thickness requirement of the process. When setting the size of the flow channel geometry, the wall thickness requirement of the minimum wall thickness requirement of the processing process must be strictly met; Use Boolean operations to sum the flow channel geometries to obtain the flow channel entity of the cylinder head model, and then use Boolean operations to subtract the cylinder head model that has completed the air channel modeling from the flow channel entity of the cylinder head model to obtain the cylinder head model that has completed the air channel and flow channel modeling; after the external features, air channels, assembly features and flow channels of the cylinder head are modeled, use stretching, rotation, and stitching surfaces to establish weight-reducing geometries at locations on the top plate, bottom plate, and side wall of the cylinder head that do not involve assembly and sealing, and associate the size of the weight-reducing geometries with the size of the flow channel geometries to always ensure that the minimum wall thickness on the cylinder head is greater than the minimum wall thickness requirement of the process; Use Boolean operations to subtract the cylinder head that has completed the assembly feature modeling from all weight-reducing geometries to obtain a cylinder head model that has completed parametric modeling; S12: obtaining a cooling channel model of the cylinder head through Boolean operations; deleting the weight reduction features on the cylinder head parameterized model and saving the model as copy 1; deleting the weight reduction features and channel features on the cylinder head parameterized model and saving the model as copy 2; performing subtraction between the copy 1 model and the copy 2 model through Boolean operations to obtain a cooling channel model of the cylinder head; associating the parameters of the same meaning in copy 1 and copy 2 in the expression of the cylinder head cooling channel model, wherein the parameters include parameters for controlling external features and parameters for controlling air channel features, so that the parameters of the same meaning in the two groups of expressions always remain equal during the model update process; after completing the association of the same parameters, when updating the parameters of the cylinder head cooling channel model, the external features and air channel features of copy 1 and copy 2 will be updated synchronously, ensuring that each time the cylinder head cooling channel model is updated, the final entity obtained only has the channel part of the cylinder head; S13: setting parameter initial values ​​and parameter boundary values ​​for structural parameters on the cylinder head parametric model; setting one parameter boundary value of the cylinder head parametric model as a limit parameter when the wall thickness at each position of the cylinder head is the minimum wall thickness requirement of the process, and setting the other parameter boundary value to other limit dimensions that meet the cylinder head design requirements, wherein the cylinder head design requirements include that the hydraulic diameter at each position of the flow channel shall not be less than the minimum wall thickness requirement of the process, the narrowest part of the cylinder head surface shall not be less than one third of the minimum wall thickness requirement of the process, and no interference shall occur between the cylinder head flow channel, air channel, assembly features, weight reduction features and external wall surface; Some cylinder head dimensions are the reference dimensions set when the cylinder head parametric model is modeled. The initial values ​​of the reference dimension parameters are set to the initial values ​​used when the cylinder head parametric model is modeled, and then the boundary values ​​are equal to the reference values. These dimensions do not change when the model is updated. After the upper and lower boundary values ​​of the parameter changes are determined for the parameters other than the reference dimensions, the initial values ​​of the parameters other than the reference dimensions are set to the median of the upper and lower boundary values ​​to reduce the probability of errors when the cylinder head parametric model is updated. S14: gradually modify the cylinder head parametric model by combining "global parameter change with error feature modification"; when the cylinder head parametric model selects parameter values ​​within the parameter variation range obtained in S13 and substitutes them into the expression to update the model, and the model update exceeds the preset number of times without error, it is determined that the parameter stability of the cylinder head parametric model meets the conditions required for optimization; modify the error feature and gradually improve the cylinder head parametric model; name all parameters except the reference size in the cylinder head parametric model expression, configure the data interface between Excel software and UG software, and import the parameter names of the cylinder head except the reference size and their corresponding parameter variation range into the Excel table, insert a random number formula to randomly select a parameter value within the variation range for all parameters except the reference size, select all random parameter values ​​generated by the random number formula together with the names of all parameters except the reference size as the data source of the cylinder head parametric model, and use the Excel table to drive UG to update the model multiple times to test the parameter stability of the cylinder head parametric model under random parameter values; When the cylinder head parametric model does not report an error when the random parameter values ​​are used for ten consecutive times to update the model, the parameter stability of the cylinder head parametric model is determined to be qualified; if an error occurs, the error feature prompted in the UG software is modified or the size variation range corresponding to the feature is modified until the cylinder head parametric model is updated ten consecutive times with random parameter values ​​without reporting an error; S15: Classify the faces on the cylinder head parameterized model and the cylinder head cooling channel model that need to be assigned different boundary conditions, and save the cylinder head parameterized model and the cylinder head cooling channel model in the form of surface features; when performing automatic calculation of the cylinder head heat transfer performance, boundary conditions can only be automatically assigned to surface features, and extracting the surfaces of the cylinder head parameterized model and the cylinder head cooling channel model into multiple surface features based on the type of boundary condition area can achieve the effect of automatically identifying the boundary condition area in the solver; Based on the cylinder head heat transfer analysis method, the cylinder head parameterized model and the cylinder head cooling channel model are classified into the surface features. The surfaces on the cylinder head model are classified, and the surface categories include water inlet, water outlet, flow channel wall, fluid-solid coupling surface, symmetry surface, outer wall, intake channel wall, exhaust channel wall and fire surface; these surfaces are extracted into surface features according to categories on the cylinder head parameterized model and the cylinder head cooling channel model by a modeling method of extracting geometric features, and the original entity models in the cylinder head parameterized model and the cylinder head cooling channel model are hidden, and the cylinder head parameterized model and the cylinder head cooling channel model in the form of surface features are obtained and saved separately, and all surface features are set to be associated with the hidden cylinder head and cylinder head cooling channel entities; S16: Automatic update of the cylinder head model is realized by calling the API function of UG; calling the API function of UG to realize the functions of reading the cylinder head parameterized model path and the cylinder head cooling channel model path, reading the cylinder head parameterized model expression path, automatically updating the cylinder head parameterized model and the cylinder head cooling channel model using the expression parameter value, and saving the cylinder head parameterized model and the cylinder head cooling channel model corresponding to the new parameter value, so as to realize one-key automatic update of the cylinder head parameterized model and the cylinder head cooling channel model.

5. The method for optimizing the heat transfer performance of a cylinder head based on the joint simulation technology according to claim 4, characterized in that: The specific implementation method of step 2 is: S21: Meshing the cylinder head parametric model and the cylinder head cooling channel model respectively; meshing with the minimum wall thickness requirement of the process as the initial mesh size to ensure the mesh quality at the minimum position of the cylinder head wall; importing the cylinder head parametric model and the cylinder head cooling channel model into ICEM; The mesh size is set to the minimum wall thickness requirement of the process, and the surface mesh is divided by using the Patch Independent meshing method; the geometric shape distortion includes the presence of broken surfaces on the cylinder head parameterized model and the cylinder head cooling channel model, a narrow surface with a width less than the minimum wall thickness requirement of the process, or an angle between two surfaces less than 15°; the cylinder head and the cylinder head cooling channel are meshed separately, and the surface mesh models of the cylinder head and the cylinder head cooling channel are output and saved; S22: merging the surface mesh models of the cylinder head and the cylinder head cooling channel; when calculating the heat transfer performance of the cylinder head, the mesh models of the cylinder head and the cylinder head cooling channel need to set boundary conditions. After the meshes of the cylinder head and the cylinder head cooling channel are drawn, the mesh models of the cylinder head and the cylinder head cooling channel are merged and calculated to achieve simultaneous setting of the boundary conditions of the cylinder head and the cylinder head cooling channel; the surface mesh models of the cylinder head and the cylinder head cooling channel are successively imported into ICEM, and the two meshes are merged to obtain a merged cylinder head surface mesh model; S23: Improve the mesh quality of the merged cylinder head surface mesh model; The surface mesh automatically drawn by ICEM is not of high quality. If the volume mesh is directly drawn in ICEM and applied to the calculation, the calculation cannot converge. The merged cylinder head surface mesh model is imported into fluent meshing to fix the mesh problem and perform volume mesh division to improve the mesh quality. In ICEM, the mesh areas in the merged cylinder head surface mesh model are named according to the water inlet, water outlet, flow channel wall, fluid-solid coupling surface, symmetry surface, outer wall, intake duct wall, exhaust duct wall and firepower surface. Import the merged cylinder head surface mesh model into fluent meshing, correct the free edge, self-intersection and repeated mesh problems, and reduce the mesh distortion to below the preset distortion; Draw the volume mesh model of the cylinder head based on the merged cylinder head surface mesh model, and repair the low-quality mesh based on the mesh node movement algorithm to reduce the inverse orthogonal quality to below the preset inverse orthogonal quality; output the volume mesh model of the cylinder head; S24: Set up simulation based on the cylinder head heat transfer analysis method, perform simulation analysis of the steady-state flow field and temperature field inside the cylinder head, and obtain the temperature distribution at each position on the cylinder head; import the body mesh model of the cylinder head into fluent, set the scale of the simulation analysis, the calculation method used for the flow field calculation, and the material properties of the cylinder head and the coolant in the flow channel; set the surface type of each surface on the cylinder head body mesh model, the surfaces include water inlet, water outlet, flow channel wall, fluid-solid coupling surface, symmetry surface, outer wall, intake channel wall, exhaust channel wall and fire surface, and the surface types include inlet surface, outlet surface, wall surface and interface surface; set the surface type of each fluid-solid coupling surface on the cylinder head and cylinder head cooling flow channel mesh model as an interface, and set the two fluid-solid coupling surfaces as a coupling relationship; set the convection heat transfer coefficient and the initial wall temperature of the various surfaces; set monitoring and shutdown conditions for the calculation process and initialize the simulation, and submit the simulation calculation to obtain the temperature field simulation result of the cylinder head; S25: Perform mesh independence analysis on the calculation of the heat transfer performance of the cylinder head; starting from the initial value of the mesh size required by the minimum wall thickness of the process, expand or reduce the mesh size used when drawing the mesh model of the cylinder head and the cylinder head cooling channel surface, calculate the temperature field simulation results of the cylinder head at different mesh sizes, compare the effects of different mesh sizes on the calculation time and calculation results, select a mesh size with a short calculation time and a small deviation in calculation results from other mesh sizes as the finite element mesh size used for optimization, and complete the mesh independence analysis.

6. The method for optimizing the heat transfer performance of a cylinder head based on the joint simulation technology according to claim 5, characterized in that: The specific implementation method of step three is: S31: adjusting the structural parameters of the cylinder head model, automatically updating the cylinder head model and the cylinder head cooling channel model, and generating a cylinder head model with parameters different from the initial values; modifying all parameters except the reference size in the expression of the cylinder head parameterized model, calling the API function of UG, reading the cylinder head parameterized model expression, and automatically updating the cylinder head parameterized model and the cylinder head cooling channel model with one key; S32: script for recording the mesh model division and mesh merging of the cylinder head and cylinder head cooling channel surface; Based on the mesh size determined after mesh independence analysis, start script recording in ICEM, use PatchIndependent meshing method to divide the surface mesh models of the cylinder head and cylinder head cooling channel, save the surface mesh models of the cylinder head and cylinder head cooling channel, and obtain the script for the surface meshing link; Start script recording in ICEM, import the surface mesh models of the cylinder head and the cylinder head cooling channel in turn, merge the two meshes, and name the mesh areas in the cylinder head surface mesh model according to the water inlet, water outlet, channel wall, fluid-solid coupling surface, symmetry surface, outer wall, intake duct wall, exhaust duct wall, and fire surface; obtain the merged cylinder head surface mesh model and the script for the mesh merging process; S33: Record the script for the cylinder head body meshing process; start the script recording in fluent meshing, import the merged cylinder head surface mesh model, correct the three problems of free edges, self-intersection and repeated meshes, and reduce the mesh distortion to below the preset distortion; Draw the volume mesh model of the cylinder head, and repair the low-quality mesh based on the mesh node movement algorithm to reduce the inverse orthogonal quality to below the preset inverse orthogonal quality; output the volume mesh model of the cylinder head and obtain the script for the volume mesh division link; S34: Record the script for calculating the heat transfer performance of the cylinder head; start the script recording in Fluent, import the volume mesh model of the cylinder head, set the scale of the simulation analysis, the calculation method used for the flow field calculation, and the material properties of the cylinder head and the coolant in the flow channel; set the surface type of each surface on the cylinder head volume mesh model, the surfaces include the water inlet, water outlet, flow channel wall, fluid-solid coupling surface, symmetry surface, outer wall, intake channel wall, exhaust channel wall and fire surface, the surface types include inlet surface, outlet surface, wall surface and interface surface; set the surface type of the fluid-solid coupling surface on the cylinder head and cylinder head cooling channel mesh model to interface surface, and set the two fluid-solid coupling surfaces to Coupling relationship; setting the convective heat transfer coefficient and the initial wall temperature of the various surfaces; setting monitoring and shutdown conditions for the calculation process and initializing the simulation, submitting the simulation calculation to obtain the temperature field simulation result of the cylinder head; extracting index data that can characterize the heat transfer performance of the cylinder head, the indexes include surface average convective heat transfer coefficient, surface average pressure, surface average y+ value, surface minimum y+ value, surface maximum y+ value, body average water cavity temperature, body average cylinder head temperature, body average speed, total mass of the cylinder head, maximum temperature of the cylinder head, maximum temperature in the water cavity, maximum speed in the water cavity, minimum temperature in the water cavity and water cavity size; outputting a cylinder head heat transfer performance example and obtaining a script for the cylinder head heat transfer performance calculation link.

7. The cylinder head heat transfer performance optimization method based on joint simulation technology as claimed in claim 6, characterized in that: The specific implementation method of step 4 is: S41: Build a cylinder head heat transfer performance optimization model in Isight, set the total number of samples according to the computing power conditions, and use the Latin hypercube algorithm to plan the sample space for cylinder head heat transfer performance optimization, so that the sample points are evenly distributed in the high-dimensional Euclidean space to ensure the quality of sample data; call the script recorded during the cylinder head heat transfer calculation process through batch commands, and use different modules to execute the cylinder head model and cylinder head cooling channel model update, cylinder head mesh drawing, cylinder head heat transfer performance calculation, and heat transfer performance index data extraction commands; After the setup is completed, the cylinder head heat transfer performance optimization model is automatically run to obtain a sample data set that characterizes the corresponding relationship between the cylinder head structure and the heat transfer performance; S42: Establish a comprehensive evaluation function, comprehensively consider the fluctuation degree and importance of multiple cylinder head heat transfer performance indicators, and score the heat transfer performance of each sample point. As a preferred embodiment, the comprehensive evaluation function is shown in the following formula: Among them, g j is the comprehensive score of the jth evaluated sample point, λ i is the weight of the i-th evaluated indicator, y ij is the actual value of the i-th evaluated indicator of the j-th evaluated sample point, Z i is the ideal value of the i-th evaluated indicator of the evaluated sample point, σ i is the standard deviation of the i-th evaluated indicator data, and n is the total number of indicators evaluated at the sample point. The weight of the i-th evaluated indicator can be calculated using the following formula: Xi is the significance coefficient of the ith indicator. The larger the Xi is, the greater the impact of the ith indicator on the comprehensive evaluation result, and the higher the weight is. The significance coefficient Ci can be expressed by the product of the standard deviation σi and the correlation coefficient Ri, that is: C=σiRi(3) The standard deviation σi is calculated using the following formula: Where m is the total number of sample points used to calculate the standard deviation, xij is the dimensionless data of the i-th performance indicator of the j-th sample point, is the dimensionless data average of the i-th performance indicator. The dimensionless data of the i-th performance indicator at the j-th sample point can be dimensionlessized by the following formula to obtain the data average: The correlation coefficient Ri is calculated using the following formula: rik is the linear correlation coefficient between the i-th indicator and the k-th indicator, which can be calculated using the following formula: After calculating all the above variables according to the sample data set, each sample point is scored through the comprehensive evaluation function, and the group of samples with the best scores are selected as the optimization results to obtain the optimal cylinder head structure in the sample space, that is, to achieve the optimization of the heat transfer performance of the cylinder head based on the joint simulation technology.

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