A method for determining the performance of an engine cooling fan based on fluid-structure interaction

Abstract

This invention discloses a method for determining the performance of an engine cooling fan based on fluid-structure interaction (FSI). The method includes the following steps: establishing a three-dimensional geometric model based on the cooling fan structure; establishing a finite element model of the fan and a finite element model of the external flow field; importing the finite element model of the fan into finite element software, assigning material properties, and setting boundary conditions; importing the finite element model of the external flow field into computational fluid dynamics (CFD) software, setting a turbulence model and boundary conditions; setting the coupling surface as the blade surface, matching the mesh nodes on the coupling surface using a neighborhood search algorithm, and transferring physical quantities between the two coupled systems using interpolation methods; and performing post-processing analysis on the calculation results of the fan structure and flow field in their respective software. This calculation method overcomes, to a certain extent, the inaccuracies of individual finite element models and computational fluid dynamics models caused by deficiencies in modeling methods, establishing an accurate FSI simulation model for calculating the cooling fan performance, while ensuring both calculation accuracy and efficiency.

Description

Technical Field

[0001] This invention relates to the field of automotive engine cooling fan development, and particularly to a method for determining the performance of an engine cooling fan based on fluid-structure interaction. Background Technology

[0002] The cooling fan in a car is a crucial component of the engine cooling system, and its aerodynamic performance has always been a focus of research. During actual operation, the cooling fan drives airflow through its own rotation. The fan blades deform under the combined effects of centrifugal force and air pressure, and this deformation also influences the airflow. For the fluid-structure interaction (FSI) effects present on the blades, neither structural analysis nor flow field analysis alone can accurately simulate the actual situation. Therefore, it is necessary to apply the FSI method to the simulation analysis of cooling fans.

[0003] In their Chinese invention patent "A Method for Calculating the Aerodynamic Performance of an Automobile Windshield," Pan Denghui et al. provided a steady-state simulation model and calculation method for the aerodynamic performance of a cooling fan. However, this model does not consider the influence of cooling fan deformation, resulting in certain errors. For fans with higher speeds and larger diameters, where blade deformation is greater, the accuracy of this calculation method is poor.

[0004] Current research on fluid-structure interaction (FSI) models focuses on fields such as aero-engines, wind turbines, and compressors. Some researchers have also considered the impact of airflow on cooling fans, establishing unidirectional FSI models to predict stress distribution, deformation distribution, and modalities of fan blades, achieving some results. However, performance analysis of engine cooling fans is mainly conducted through separate computational fluid dynamics simulations, where the fan is often considered a rigid wall, which can lead to inaccurate models.

[0005] Fluid-structure interaction (FSI) analysis can generally be divided into strong coupling and weak coupling. Strong coupling involves constructing the governing equations of the coupled system and directly solving them numerically. While strong coupling can yield more accurate solutions, it is computationally expensive and convergence is difficult. In weak coupling, only the fluid and solid systems need to be solved separately. At the end of the coupling time step, data exchange of coupling quantities between the two systems is achieved through interpolation, thus obtaining the solution for the coupled system. Weak coupling does not consider the coupling effects between physical fields in a single increment step, significantly improving computational efficiency. In weak FSI methods, if only the influence of the fluid on the solid is considered, it is called unidirectional FSI; if the mutual influence between the fluid and solid is considered, it is called bidirectional FSI.

[0006] In conclusion, it is necessary to develop a bidirectional, weak fluid-structure interaction modeling method for engine cooling fans and a method for determining the performance of cooling fans. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for determining the performance of engine cooling fans based on fluid-structure interaction, which can simultaneously predict the structural strength and aerodynamic performance of cooling fans. This calculation method solves the problem of inaccurate simulation models to a certain extent, while ensuring computational efficiency and reducing computational costs. It can be used to study the deformation and aerodynamic performance of cooling fans.

[0008] To achieve the objective of this invention, a method for determining the performance of an engine cooling fan based on fluid-structure interaction is provided, comprising the following steps:

[0009] Step 1: Create a geometric model of the cooling fan in 3D modeling software;

[0010] Step 2: Mesh the geometric model of the cooling fan using preprocessing software to generate a finite element model of the cooling fan; establish a finite element model of the external flow field based on the finite element model of the cooling fan and the aerodynamic performance test bench.

[0011] Step 3: Import the finite element model of the cooling fan into the structural analysis software and set the material parameters and boundary conditions; import the finite element model of the external flow field into the computational fluid dynamics software and set the turbulence model and boundary conditions.

[0012] Step 4: Set the coupling surface and the physical quantities to be exchanged, match the mesh nodes of the coupling surface to realize data exchange between the structural system and the fluid system, and start the simulation calculation to obtain the structural strength and aerodynamic performance of the cooling fan. During the data exchange, the time increment step is set for the structural analysis software, and the sub-loop iteration is used for the computational fluid dynamics software. The structural analysis software uses the data transferred from the computational fluid dynamics software as boundary conditions for calculation and transfers the calculated data back to the computational fluid dynamics software for boundary update.

[0013] Step 5: Post-process the calculation results in finite element software and computational fluid dynamics software respectively to obtain the blade stress distribution, deformation distribution, and cooling fan static pressure, torque, and shaft power.

[0014] Furthermore, the established finite element model of the cooling fan includes a fan blade model and a support plate model. The complete blade model is generated by rotating and copying a single blade model, and after sharing nodes with the support plate model, the finite element model of the cooling fan is generated.

[0015] Furthermore, the established external flow field finite element model includes a rotating region, a transition region, and inlet and outlet regions. The rotating region and the transition region are discretized using tetrahedral meshes, while the inlet and outlet regions are discretized using hexahedral elements. The mesh size gradually increases from the rotating region to the transition region and the inlet and outlet regions.

[0016] Furthermore, when establishing the fluid-structure interaction model of the cooling fan, the established fan blade surface mesh is copied, and a finite element model of the cooling fan and an external flow field finite element model are generated respectively, while the distribution of mesh nodes on the surface of the cooling fan blade remains consistent.

[0017] Furthermore, computational fluid dynamics software was used to solve the Reynolds-averaged Navier-Stokes equations. The RNG k-epsilon turbulence model, which is suitable for handling rotating flows, was adopted. The multiple reference frame method was used to handle the rotating region. The semi-implicit method of pressure coupling equations was used to iteratively solve the equations. The inlet was a mass flow rate inlet and the outlet was a pressure outlet.

[0018] Furthermore, the surface of the cooling fan blades is a fluid-structure interaction surface, and data exchange exists between the two systems at the mesh nodes of the interaction surface. The exchanged physical quantities should satisfy conservation relationships:

[0019]

[0020]

[0021] In the formula, τ is stress, d is displacement, n is direction cosine, and the subscripts f and s represent the fluid and solid coupling surfaces, respectively.

[0022] Furthermore, the data exchange on the coupling surface includes: the computational fluid dynamics software transmits the calculated "relative pressure" to the structural analysis software, the structural analysis software uses the "relative pressure" as a boundary condition to calculate the blade deformation, and feeds back the deformed "node position" to the computational fluid dynamics software as a new blade boundary.

[0023] Furthermore, a relaxation factor is applied to the "relative pressure" to avoid excessive pressure peaks in the early stages of iterative calculation, which could lead to excessive blade deformation and the generation of negative volume grid cells.

[0024] Furthermore, the structural analysis software uses a fixed time step, while the computational fluid dynamics software initiates a sub-loop iteration. Within this sub-loop, no data exchange occurs between the two systems, thereby reducing the number of coupling iterations and improving computational efficiency.

[0025] Furthermore, the dynamic mesh function was enabled for the blade boundaries in the computational fluid dynamics model, and the quality of the dynamic mesh elements was optimized using the smooth mesh method and local mesh reconstruction technique.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] 1) The present invention provides a method for determining the performance of an engine cooling fan based on fluid-structure interaction, which can simultaneously perform simulation analysis on the structural strength and aerodynamic performance of the cooling fan.

[0028] 2) The engine cooling fan performance determination method based on fluid-structure interaction provided by the present invention has a model with strong stability, and large mesh deformation can be achieved by controlling the relaxation factor and dynamic mesh function.

[0029] 3) The method for determining the performance of an engine cooling fan based on fluid-structure interaction provided by this invention considers the influence of aerodynamic pressure when simulating the structural strength of the cooling fan; and considers the influence of blade deformation when simulating the aerodynamic performance of the cooling fan, which can improve the accuracy of the model while ensuring computational efficiency. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a fluid-structure interaction model provided in an embodiment of the present invention.

[0031] Figure 2 This is a schematic diagram of a cooling fan structure provided in an embodiment of the present invention.

[0032] Figure 3 This is a schematic diagram of the fan support structure provided in an embodiment of the present invention.

[0033] Figure 4 This is a schematic diagram of a finite element model of a cooling fan provided in an embodiment of the present invention.

[0034] Figure 5 This is a schematic diagram of the finite element model of the rotating region provided in an embodiment of the present invention.

[0035] Figure 6 A schematic diagram of the computational fluid dynamics model of the external flow field provided in an embodiment of the present invention.

[0036] Figure 7 The flowchart is a fluid-structure interaction modeling method provided in an embodiment of the present invention.

[0037] Figure 8 A diagram illustrating the physical quantity exchange process provided in an embodiment of the present invention.

[0038] Figures 9(a) to 9(c) are schematic diagrams of the calculation results of the aerodynamic performance of the cooling fan provided in the embodiments of the present invention.

[0039] Figure 10 This is a schematic diagram of the calculation results of the deformation of the cooling fan blades provided in an embodiment of the present invention. Detailed Implementation

[0040] The invention will now be described in more detail through a specific embodiment. It should be noted that the embodiment includes many specific details to enable a fuller understanding of the implementation, but the implementation of the invention is not limited to the following embodiment, and any modifications and / or alterations made to the invention will fall within the scope of protection of the invention.

[0041] Please see Figures 1-10 The present invention provides a method for determining the performance of an engine cooling fan based on fluid-structure interaction. First, a fluid-structure interaction simulation model of the cooling fan needs to be established (see...). Figure 1 ), divided into cooling fan model and external flow field model (see Figures 2-6 ), including the following steps:

[0042] Step 1: Establish the geometric model of the cooling fan.

[0043] In some embodiments of the present invention, the established cooling fan geometric model is as follows: Figure 2 As shown, the cooling fan has a diameter of 650mm, 7 blades, an outer hub diameter of 240mm, and an inner hub diameter of 205mm. It is understood that in other embodiments, the parameters of the cooling fan can be set to other values.

[0044] In some embodiments of the present invention, the fan support plate in the cooling fan has a diameter of 210 mm and a thickness of 4 mm; 24 circular holes with a diameter of 12 mm are distributed on the fan support plate along a circumference with a diameter of 180 mm for connecting to the fan; and 6 mounting holes with a diameter of 10.6 mm are distributed on the fan support plate along a circumference with a diameter of 89 mm for mounting a silicone oil clutch. The fan support plate model is as follows. Figure 3 As shown.

[0045] In step one, a geometric model of the cooling fan is established using 3D modeling software. The Z-axis is perpendicular to the fan's rotation plane. According to the right-hand rule, the negative direction of the Z-axis is determined to be the fan's rotation direction, and the positive direction of the Z-axis is the incoming flow direction.

[0046] Step 2: Establish the finite element model of the cooling fan and the finite element model of the external flow field.

[0047] In some embodiments of the present invention, the established geometric model file of the cooling fan is imported into pre-processing software for mesh generation to produce a finite element model of the cooling fan. Considering the relatively complex blade structure, triangular elements are used for meshing the entire geometric model of the cooling fan. The blade tips and edges have a significant impact on the flow field, so 2.5mm mesh elements are used there, while 5mm mesh elements are used at the blade center; 2.5mm mesh elements are used for the fan support plate. The finite element models of the cooling fan blades and support plate are as follows: Figure 4 As shown.

[0048] In some embodiments of the present invention, the fan blades are equidistant. When establishing the finite element model, one-seventh of the blades can be selected for meshing, and the mesh elements of a single blade can be rotated and copied to obtain the overall finite element model of the cooling fan. It is important to note that when meshing a single blade, the arrangement of mesh nodes on the blade's periodic boundaries must be consistent so that after rotation and copying, all boundaries will share nodes.

[0049] After generating the finite element model of the cooling fan, the tetrahedral elements need to be optimized to ensure that the Vol skew of all tetrahedral elements is below 0.85 and the Tet collapse is above 0.2. Finally, the tetrahedral element type is converted to an improved ten-node tetrahedral element.

[0050] In some embodiments of the present invention, the fan aerodynamic performance testing device is selected from the Type A air chamber device (free inlet-free outlet) in the national standard GB-T1236-2000 "Performance Testing of Standardized Air Ducts for Industrial Ventilators". The finite element model of the entire external flow field is established proportionally based on the actual dimensions of the air chamber test bench, and unnecessary structures are reasonably simplified, such as ignoring auxiliary fans, rectifiers, and drive motors. The air chamber inlet is a square plane of 3000mm × 3000mm, and the air chamber length is 4000mm; behind the air chamber is a free fluid region with a diameter of 7000mm and a length of 5000mm, used to simulate the space entered by air flowing through the fan.

[0051] The finite element model of the external flow field established in step two includes a rotating region, a transition region, and inlet and outlet regions. In some embodiments of the present invention, the rotating region is a cylindrical region with a diameter of 680 mm and a length of 165 mm near the fan; the transition region is a cylindrical region with a diameter of 1685 mm and a length of 1480 mm, and the rotating region is located at the center of the transition region; the transition region is connected to the inlet and outlet regions.

[0052] In some embodiments of the present invention, in order to control the overall number of meshes and ensure the accuracy of the model, the air rotation area near the fan is divided into denser units as much as possible, while larger units are used near the inlet and outlet areas, and the unit size increases as gradually as possible from the fan surface outwards.

[0053] In some embodiments of the present invention, the outer surface of the rotating area is meshed using 12mm triangular units. The enclosed space formed by the surface mesh of the rotating area and the surface mesh of the internal cooling fan is filled with tetrahedral mesh units. The tetrahedral units are generated using interpolation to ensure a smooth change in the size distribution of the mesh units within the rotating area. Figure 5 As shown, the outer surface of the transition zone is meshed using 40mm triangular elements, which, together with the surface mesh of the rotation zone, generate tetrahedral mesh elements for the transition zone. These tetrahedral elements can be generated using standard methods to reduce the number of meshes. The inlet and outlet regions, being far from the fan and having regular shapes, can be discretized using hexahedral elements, generated by stretching and rotating quadrilateral mesh elements. Finally, the tetrahedral elements in the transition and rotation zones need to be optimized to ensure that the twist rate of all tetrahedral elements is below 0.85 and the element collapse rate is above 0.2.

[0054] Step 3: Import the finite element model of the cooling fan into the structural analysis software and set the material parameters and boundary conditions; import the finite element model of the external flow field into the computational fluid dynamics software and set the turbulence model and boundary conditions.

[0055] The established finite element model of the cooling fan is exported as a file that can be recognized by structural analysis software, imported into the structural analysis software, and material parameters and boundary conditions are set. In some embodiments of the present invention, the blade material is engineering plastic PA6 with an elastic modulus of 7.71 × 10⁻⁶. 3 MPa, Poisson's ratio is 0.41, and density is 1.36 × 10⁻⁶. -9 t / mm 3 The pallet material is Q235 carbon steel, with an elastic modulus of 2.1 × 10⁻⁶. 5 MPa, Poisson's ratio is 0.274, and density is 7.83 × 10⁻⁶. -9 t / mm 3 Full constraints were applied to the six mounting holes on the support plate, and a rotational speed of 2100 rpm was applied to the entire fan model using a static universal analysis step. Additionally, the fan blade surface mesh elements were extracted as fluid-structure interaction surfaces.

[0056] Computational fluid dynamics software was used to solve the governing equations of the flow field, namely the continuity equation, the momentum equation (Navier-Stokes equations), and the energy equation. A semi-implicit method using the pressure coupling equations was employed for iterative solution of the momentum equation.

[0057] In some embodiments of this invention, the established finite element model of the external flow field is imported into computational fluid dynamics software and solved using a steady-state, pressure-based solver. The ambient pressure is set to standard atmospheric pressure, and the effects of temperature and gravity are not considered. The turbulence model uses the RNG k-epsilon model, suitable for handling rotating flows, in which the standard wall equations are used to handle the near-wall region. The multi-reference method is used to handle the rotating region, and the rotational speed is kept consistent with the fan speed. A mass flow rate inlet is selected, with different air mass flow rates given experimentally. A pressure outlet is selected, and the relative pressure at the outlet is set to zero, indicating that it is connected to the atmosphere. The fan surface is set as the rotating wall. In addition, the hexahedral and tetrahedral meshes in the model do not share nodes. To ensure normal data transmission, the surface meshes here need to be set as data interaction surfaces.

[0058] In addition, the meshing function needs to be enabled on the blade boundary of the finite element model of the external flow field. In order to avoid poor mesh quality after blade deformation, the smooth meshing method and local mesh reconstruction technology are used to optimize the mesh quality, and the maximum element distortion rate is limited to 0.85.

[0059] Step 4: Set the coupling surface and the physical quantities to be exchanged, match the mesh nodes of the coupling surface to realize the data exchange between the structural system and the fluid system, and start the simulation calculation to obtain the deformation and aerodynamic performance of the cooling fan.

[0060] Import the configured finite element model of the cooling fan and the finite element model of the external flow field into the multiphysics coupling interface software for scanning, and set the unit system in the structural analysis software to SI-mm-ts. Select the fan blade surface as the fluid-structure interaction surface. During the co-simulation, the blade structure deforms under air pressure, and this deformation also alters the fluid boundary. For the physical quantities exchanged on the coupling surface, the conservation equations must be satisfied:

[0061]

[0062]

[0063] In the formula, τ is stress, d is displacement, n is direction cosine, and the subscript is... , These represent the fluid and solid coupling surfaces, respectively.

[0064] In some embodiments of the present invention, the multiphysics coupling interface software employs MpCCI.

[0065] Figure 7 , Figure 8 The diagram illustrates the calculation method and physical quantity exchange process of this invention. For structural analysis software, a fixed time increment step (e.g., 0.1s) is used, with a total calculation time of 1 second. For computational fluid dynamics software, a sub-loop iteration is used, set to 200 steps, for a total of 2000 iterations. No data exchange occurs between the two systems within the sub-loop, thereby reducing the number of coupling iterations and improving computational efficiency. The coupled calculation flow is as follows:

[0066] 1. The calculation was initiated by computational fluid dynamics software. After 200 iterations, the calculation was paused, and the obtained "relative pressure" was passed to the structural analysis software through interpolation.

[0067] 2. After receiving the data, the structural analysis software uses it as boundary conditions to calculate a time increment step, obtains the "node positions" of each fan blade, and transmits it back to the computational fluid dynamics software.

[0068] 3. The computational fluid dynamics software uses dynamic mesh technology to update the blade boundaries and begin the next round of coupled calculations.

[0069] In some embodiments of the present invention, a step relaxation factor is applied to the "relative pressure" with an initial value of 0.1 and an increment of 0.1 after each data exchange, in order to avoid excessively large initial calculated pressure peaks, which could lead to excessive blade deformation and the generation of negative volume grid cells.

[0070] Step 5: Post-process the calculation results in the structural analysis software and computational fluid dynamics software respectively to obtain the blade stress distribution, deformation distribution, and cooling fan static pressure, torque, and shaft power.

[0071] In some embodiments of the present invention, the calculation results of the cooling fan's structural strength and aerodynamic performance are post-processed in corresponding structural analysis software and computational fluid dynamics software, respectively. The aerodynamic performance of the cooling fan includes static pressure-flow rate curves, power-flow rate curves, and efficiency-flow rate curves. The static pressure of the cooling fan... Shaft power and efficiency It can be calculated using the following formula:

[0072]

[0073] In the formula, It is the cross-sectional pressure at the outlet of the air chamber device, i.e., the test atmospheric pressure. It is the pressure at the detection surface.

[0074]

[0075] In the formula, This refers to the torque of the cooling fan; This refers to the rotational speed of the cooling fan.

[0076]

[0077] In the formula, For airflow, For fan static pressure, This refers to the fan power.

[0078] Figures 9(a) to 9(c) Figure 10 The calculation results of the aerodynamic performance and structural strength of the cooling fan in this embodiment were obtained by using the multiple reference frame method (MRF) without considering fan deformation and the two-way, weak fluid-structure interaction method considering fan deformation. It can be seen that, compared with the multiple reference frame method, the simulation results of the fluid-structure interaction method provided by this invention are closer to the experimental results after considering the influence of cooling fan deformation on the flow field, and the consistency is well maintained, which verifies the correctness of the model.

[0079] The proposed method for calculating the performance of engine cooling fans based on fluid-structure interaction employs bidirectional, weak fluid-structure interaction, simultaneously simulating and analyzing the structural strength and aerodynamic performance of the cooling fan. This method overcomes, to a certain extent, the inaccuracies of separate finite element models and computational fluid dynamics models caused by deficiencies in modeling methods, while ensuring computational efficiency. It can be applied to the development of cooling fans.

[0080] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for determining the performance of an engine cooling fan based on fluid-structure interaction, characterized in that, Includes the following steps: Step 1: Create a geometric model of the cooling fan in 3D modeling software; Step 2: Mesh the geometric model of the cooling fan using preprocessing software to generate a finite element model of the cooling fan; establish a finite element model of the external flow field based on the finite element model of the cooling fan and the aerodynamic performance test bench. Step 3: Import the finite element model of the cooling fan into the structural analysis software and set the material parameters and boundary conditions; import the finite element model of the external flow field into the computational fluid dynamics software and set the turbulence model and boundary conditions; use the computational fluid dynamics software to solve the governing equations of the flow field. The turbulence model adopts the RNG k-epsilon turbulence model, the multiple reference frame method is used to handle the rotating region, and the momentum equation is solved iteratively using the semi-implicit method of the pressure coupling equation set. The inlet adopts the mass flow rate inlet and the outlet adopts the pressure outlet. Step 4: Define the coupling surface and the physical quantities exchanged. Match the mesh nodes of the coupling surface to achieve data exchange between the structural system and the fluid system, and begin simulation calculations to obtain the structural strength and aerodynamic performance of the cooling fan. During data exchange, set a time increment step for the structural analysis software and use a sub-loop iteration for the computational fluid dynamics (CFD) software. The structural analysis software uses the data transferred from the CFD software as boundary conditions for calculation and then transfers the calculated data back to the CFD software for boundary updates. The surface of the cooling fan blades is selected as the fluid-structure interaction surface. Data exchange exists between the two systems at the mesh nodes of the coupling surface, and the exchanged physical quantities should satisfy conservation relationships. In the formula, τ is stress, d is displacement, n is direction cosine, and the subscripts f and s represent the fluid and solid coupling surfaces, respectively. The data exchange on the coupling surface includes the relative pressure at the mesh nodes on the blade surface and the position of the surface mesh nodes after the blade is deformed. Step 5: Post-process the calculation results in finite element software and computational fluid dynamics software respectively to obtain the blade stress distribution, deformation distribution, and cooling fan static pressure, torque, and shaft power.

2. The method for calculating the performance of an engine cooling fan based on fluid-structure interaction according to claim 1, characterized in that, In step two, the finite element model of the cooling fan includes a fan blade model and a support plate model. The complete blade model is generated by rotating and copying a single blade model, and then sharing nodes with the support plate model to generate the finite element model of the cooling fan.

3. The method for calculating the performance of an engine cooling fan based on fluid-structure interaction according to claim 1, characterized in that, In step two, the established finite element model of the external flow field includes a rotating region, a transition region, and inlet and outlet regions. The rotating region and the transition region are discretized using tetrahedral elements, while the inlet and outlet regions are discretized using hexahedral elements. The mesh size gradually increases from the rotating region to the transition region and the inlet and outlet regions.

4. The method for calculating the performance of an engine cooling fan based on fluid-structure interaction according to claim 1, characterized in that, In step two, the established fan blade surface mesh is copied, and a cooling fan finite element model and an external flow field finite element model are generated respectively, with the distribution of mesh nodes on the cooling fan blade surface remaining consistent.

5. The method for calculating the performance of an engine cooling fan based on fluid-structure interaction according to claim 1, characterized in that, A relaxation factor is applied to the relative pressure.

6. The method for calculating the performance of an engine cooling fan based on fluid-structure interaction according to claim 1, characterized in that, Finite element software uses a fixed time step, while computational fluid dynamics software enables sub-loop iteration.

7. The method for calculating the performance of an engine cooling fan based on fluid-structure interaction according to claim 1, characterized in that, The dynamic mesh function is enabled for the blade boundaries in the computational fluid dynamics model, and the quality of the dynamic mesh elements is optimized using the smooth mesh method and local mesh reconstruction technique.

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