CN-115828454-B - Engine cooling fan performance determining method based on fluid-solid coupling

CN115828454BCN 115828454 BCN115828454 BCN 115828454BCN-115828454-B

Abstract

The invention discloses an engine cooling fan performance determining method based on fluid-solid coupling, which comprises the following steps of establishing a three-dimensional geometric model according to a cooling fan structure, establishing a finite element model of a fan and a finite element model of an external flow field, importing the finite element model of the fan into finite element software to endow material properties and set boundary conditions, importing the finite element model of the external flow field into computational fluid dynamics software to set turbulence models and boundary conditions, setting a coupling surface as a blade surface, matching grid nodes on the coupling surface by utilizing a field searching algorithm, carrying out physical quantity transmission between two coupling systems by utilizing an interpolation method, and carrying out post-processing analysis on calculation results of the fan structure and the flow field in corresponding software. The method solves the problem that the independent finite element model and the computational fluid dynamics model are inaccurate due to the defects of the modeling method to a certain extent, establishes a fluid-solid coupling simulation model for accurate cooling fan performance calculation, and simultaneously ensures calculation accuracy and calculation efficiency.

Inventors

ZHOU ZIJIAN
DUAN YAOLONG
WANG XINLING
YU NING
YU LEIBIN
LI JUNHUI
YING RUNHAI
SHANGGUAN WENBIN

Assignees

雪龙集团股份有限公司

Dates

Publication Date: 20260505
Application Date: 20221117

Claims (7)

1. The method for determining the performance of the cooling fan of the engine based on fluid-solid coupling is characterized by comprising the following steps of: step one, establishing a geometric model of a cooling fan in three-dimensional modeling software; Step two, grid division is carried out on the geometric model of the cooling fan through preprocessing software to generate a finite element model of the cooling fan; step three, importing a finite element model of a cooling fan into structural analysis software, setting material parameters and boundary conditions, importing an external flow field finite element model into computational fluid dynamics software, setting a turbulence model and boundary conditions, adopting the computational fluid dynamics software to solve a control equation of a flow field, adopting an RNG k-epsilon turbulence model to process a rotating area by adopting a multiple reference system method, adopting a semi-implicit method of a pressure coupling equation set to carry out momentum equation iteration solution, adopting a mass flow inlet and adopting a pressure outlet by adopting an inlet; Setting a coupling surface and exchanged physical quantity, matching grid nodes of the coupling surface, realizing data exchange between a structural system and a fluid system, and starting simulation calculation to obtain structural strength and aerodynamic performance of the cooling fan, wherein when data exchange is carried out, a time increment step is set for structural analysis software, sub-loop iteration is adopted for the computational fluid dynamics software, the structural analysis software calculates data transmitted by the computational fluid dynamics software as boundary conditions and transmits the calculated data back to the computational fluid dynamics software for boundary update, the surface of a cooling fan blade is selected as a fluid-solid coupling surface, the data exchange between the two systems exists on the grid nodes of the coupling surface, and the exchanged physical quantity should satisfy a conservation relation: in the formula, tau stress, d is displacement, n is direction cosine, and subscripts f and s respectively represent fluid and solid coupling surfaces; the data exchange on the coupling surface comprises the relative pressure at the grid nodes of the surface of the blade and the positions of the grid nodes of the surface after the deformation of the blade; and fifthly, performing post-processing on the calculation result in finite element software and computational fluid dynamics software respectively to obtain blade stress distribution, deformation distribution, cooling fan static pressure, torque and shaft power.
2. The method for calculating the performance of the cooling fan of the engine based on fluid-solid coupling according to claim 1, wherein in the second step, the established finite element model of the cooling fan comprises a fan blade model and a supporting plate model, the complete blade model is generated by rotary replication of a single blade model, and the finite element model of the cooling fan is generated after the complete blade model is co-node with the supporting plate model.
3. The method for calculating the performance of an engine cooling fan based on fluid-solid coupling according to claim 1, wherein in the second step, the established finite element model of the external flow field comprises a rotation area, a transition area, an inlet area and an outlet area, the rotation area and the transition area are dispersed by adopting tetrahedral units, the inlet area and the outlet area are dispersed by adopting hexahedral units, and the mesh size is gradually increased from the rotation area to the transition area, the inlet area and the outlet area.
4. The method for calculating the performance of the cooling fan of the engine based on fluid-solid coupling according to claim 1, wherein in the second step, the established grid of the surface of the fan blade is duplicated, and a cooling fan finite element model and an external flow field finite element model are respectively generated, wherein the node distribution of the grid of the surface of the fan blade of the cooling fan is kept consistent.
5. The fluid-solid coupling-based engine cooling fan performance calculation method of claim 1, wherein a relaxation factor is applied to the relative pressure.
6. The fluid-solid coupling-based engine cooling fan performance calculation method of claim 1, wherein the finite element software uses a fixed time step and the computational fluid dynamics software starts sub-loop iterations.
7. The fluid-solid coupling-based engine cooling fan performance calculation method according to claim 1, wherein a moving grid function is turned on for a blade boundary in a computational fluid dynamics model, and a light-sequential grid method and a local grid reconstruction technique are used to optimize a moving grid cell quality.

Description

Engine cooling fan performance determining method based on fluid-solid coupling Technical Field The invention relates to the field of research and development of cooling fans of automobile engines, in particular to a method for determining performance of an engine cooling fan based on fluid-solid coupling. Background The cooling fan of an automobile is one of the important components in an engine cooling system, and its aerodynamic performance has been the focus of attention of researchers. When the cooling fan actually works, the air flow is driven through the self rotary motion, the fan blades deform under the combined action of the rotary centrifugal force and the air pressure, and meanwhile, the deformation of the blades also affects the motion of the air flow. For the fluid-solid coupling effect existing on the blade, the individual structural analysis or flow field analysis cannot accurately simulate the actual situation, so that the fluid-solid coupling method needs to be applied to the simulation analysis of the cooling fan. Pan Denghui et al in the chinese patent of invention, "a calculation method of aerodynamic performance of an automobile hood", provide a steady-state simulation model and a calculation method of aerodynamic performance of a cooling fan, where the model is built with a certain error without considering the influence of deformation of the cooling fan. For fans with higher rotating speeds and larger diameters, the deformation of the blades is larger, and the calculation method is poor in accuracy. At present, research on fluid-solid coupling models is concentrated in the fields of aeroengines, wind turbines, compressors and the like, some researchers consider the influence of air flow on cooling fans, a unidirectional fluid-solid coupling model is established, and the stress distribution, deformation distribution, modes and the like of fan blades are predicted, so that a certain result is obtained. The performance analysis of the engine cooling fan is mainly simulated by single computational fluid dynamics, and the fan is often considered to be a rigid wall surface, so that the built model is inaccurate. Fluid-solid coupling analysis can be generally classified into strong coupling and weak coupling. By constructing a control equation of the coupling system and directly solving the control equation numerically, the method is called strong coupling. Although a more accurate solution can be obtained by using strong coupling, the calculation cost is large and the convergence is difficult. In the weak coupling system, only the fluid system and the solid system are needed to be solved respectively, and when the coupling time step is finished, the data exchange of the coupling quantity is realized between the two systems through interpolation, so that the solution of the coupling system is obtained. The weak coupling method does not consider the coupling effect between the physical fields in a single increment step, so that the calculation efficiency is greatly improved. In the weak fluid-solid coupling method, the fluid-solid coupling is referred to as unidirectional fluid-solid coupling if only the influence of the fluid on the solid is considered, and the fluid-solid coupling is referred to as bidirectional fluid-solid coupling if the mutual influence between the fluid and the solid is considered. In view of the foregoing, it is necessary to develop a modeling method for bi-directional, weak fluid-solid coupling of an engine cooling fan and a determination method for cooling fan performance. Disclosure of Invention The invention aims at overcoming the defects in the prior art, and provides a method for determining the performance of an engine cooling fan based on fluid-solid coupling, which can simultaneously predict the structural strength and the pneumatic performance of the cooling fan. The calculation method solves the problem of inaccurate simulation models to a certain extent, ensures the calculation efficiency, reduces the calculation cost, and can be used for researching the deformation and the aerodynamic performance of the cooling fan. In order to achieve the purpose of the invention, the invention provides a method for determining the performance of an engine cooling fan based on fluid-solid coupling, which comprises the following steps: step one, establishing a geometric model of a cooling fan in three-dimensional modeling software; Step two, grid division is carried out on the geometric model of the cooling fan through preprocessing software to generate a finite element model of the cooling fan; Step three, leading the finite element model of the cooling fan into structural analysis software, and setting material parameters and boundary conditions; Setting a coupling surface and exchanged physical quantity, matching grid nodes of the coupling surface, realizing data exchange between a structural system and a fluid system, and starting simulation calculation to obtain stru