Research On Aerodynamic Drag And Heat Transfer Performance Of Wheel

The three major themes of automotive design, energy conservation, environmental protection and safety, make a clear requirement for the development direction of the whole automobile industry. With the rising of the car ownership in China, the shortage of energy resources, the serious pollution of the exhaust gas and the frequent accidents of automobile safety, have become an urgent problem to be solved in the social development. Vehicle aerodynamic drag is directly related to the car’s fuel consumption rate, it is an important breakthrough in automobile energy saving and emission reduction. The wheel has an important influence on the formation and development of the vehicle flow field. Therefore, it is significant to study the aerodynamic drag characteristics of the vehicle, which is significant to improve the fuel economy and reduce the emission of harmful exhaust gas. As an important part of automobile driving safety, 90 percent of the brake disc ’ s heat energy is transmitted to the air through the convection heat transfer to the wheel chamber. Through the study of the flow field around the wheel, the cooling airflow speed and the state of the brake disc surface are changed. Due to the improvement of the heat dissipation performance of the brake disc, the brake failure caused by the high temperature of the brake disc is reduced, and the safety of the automobile is improved.This paper is based on the project of National Natural Science Foundation "magnesium alloy assembly wheel structure material properties of various lightweight multi objective optimization design method"(project number: 51475201). Firstly, make the CFD simulation of independent wheel by using fluid calculation software—FLUENT. Analyz the state of air flow near the independent wheel and the influence of the shape of the spokes on the wheel aerodynamic drag.Make the numerical calculations of the flow field of the wheel under the vehicle model and the analysis of the impact on the aerodynamic drag of the vehicle and the heat transfer in the wheel cavity. Do a brief comparative analysis between the simulation analysis and the wind tunnel test data and verify the validity of the simulation results. Secondly, Analyz the number of spokes, the opening area of spokes and the styles of spokes impact on aerodynamic drag and heat transfer characteristics of wheel. Summarize the influence law and provide the basis for the optimization of the size of the spoke in detail. Finally, the finite element parametric modeling of the wheel is carried out by using the Hypermorph advanced grid deformation software and 8 parameter variables are defined. According to the optimal Latin hypercube sampling method, schedule 35 simulation tests. Develop the Kriging approximation model and select the NSGA-II optimization algorithm for multi objective optimization of the size of the wheel spoke. And get a ideal optimized lightweight design scheme with good aerodynamic characteristics and cooling performance of brake disc.Make the comparative analysis on the performance of the wheels before and after optimization. Under the premise of satisfying the wheel weight loss of 4%, the aerodynamic drag of the vehicle is reduced by 5.03% and the heat transfer inside the wheel is increased by 4.47% after optimization. At the same time, the structure and performance parameters of the wheels still meet the requirements. The feasibility of this method is verified by considering the aerodynamic drag of the whole vehicle, the cooling performance of the brake disc and the light weight of the wheel.