汽车换热器风室试验台的CFD分析

CFD analysis on wind chamber test-bed for automobile heat exchanger

为给汽车前端和发动机舱内气流数值计算提供参考依据,基于FLUENT对某汽车换热器风室试验台进行建模和数值模拟;分析风室内部空气流动状况,针对流动特征,给出风室计算流体力学(Computational Fluid Dynamics,CFD)校核的评价.网格采用四面体结构,模型中采用三维不可压的雷诺平均N-S方程,速度压力耦合采用SIMPLE方法.空间离散格式为2阶迎风格式,时间离散格式为2阶隐式.选用realizablek-ε模型模拟风室内部空气的湍流流动.固体壁面采用无滑移边界条件和非平衡壁面函数边界条件.模型进口采用速度入口来给定风量,出口采用压力出口.比较计算结果与试验设计标准,喷嘴压差的相对偏差范围在5%以内,基本达到对设备的精度要求,对风室设计有一定指导意义.

To support the airflow numerical computation of automobile front-end and engine compartment, the modeling and numerical simulation of a wind chamber test-bed for automobile heat exchanger are performed based on FLUENT; the airflow in the wind chamber is analyzed; and the Computational Fluid Dynamics （CFD） verification is evaluated according to the airflow characteristics. The 3 D uncompressible Navier-Stokes equations are solved for the model with tetrahedral mesh, and the velocity-pressure coupling is performed by SIMPLE method. The spatial discretization is second order upwind scheme and the temporal discretization is second order implicit scheme. The realizable k-ε model is used to simulate the turbulence flow for the air in the wind chamber. The velocity inlet which is used to set the wind flow rate and the pressure outlet are used for the model while the solid walls are treated as no-slip boundary conditions with unbalanced wall function. An ideal effect is obtained with the comparison between the computational results and the design criteria with less than 5% pressure drop error of the nozzle. The design basically meets the precision requirement of the equipment. So the results can provide some references for the wind chamber design.