Abstract
In the past studies, the influence of wheel structure design and optimization on the aerodynamic drag of car and heat transfer performance of brake disc was less studied. To study the influence mechanism, the finite element model for wheel aerodynamic analysis was established using computational fluid dynamic method and the correctness of the model was verified by the wind tunnel test data. The influence mechanism of the flow field on aerodynamic drag of car and wheel and heat transfer performance of brake disc was studied. The influence of wheel disc structure on aerodynamic drag coefficient of the car and average convective heat transfer coefficient of the brake discs was studied. The parametric model of the wheel under the computational fluid dynamic analysis was established using mesh morphing technology. A total of 100 and 10 sample points were extracted using the Hammersley Design and Optimal Latin Hypercube Design, respectively, to fit the radial basis function surrogate model and test the accuracy of the surrogate model. Based on the established surrogate model, taking the minimum of the wheel mass, the minimum of the aerodynamic drag coefficient of the car and the maximum of the average surface convective heat transfer coefficient of brake discs as objectives and design variables of wheel as constraints to ensure the wheel structural strength, the non-dominated sorting genetic algorithm was adopted to carry out multi-objective optimization design for the wheel. Pareto frontier was obtained and a compromise solution was selected as the optimization design result. After the optimization design, the wheel mass is reduced by 8.28%, the aerodynamic drag coefficient of the car is reduced by 3.17% and the average surface convective heat transfer coefficient of brake discs is increased by 9.31%.
Highlights
The results show a small decrease in drag performance; when increasing the number of wheel blades, the drag performance shows an improvement due to the fan effect and by closing the opening wheel area
The positive pressure region is the main reason for the formation of the aerodynamic drag, while the airflow separation in the negative pressure region will cause the vortex to generate, rotate and detach
The aerodynamic drag of front wheel is bigger than that of rear wheel, while the rear wheel has a great influence on the flow field in the rear body
Summary
Advances in Mechanical Engineering the wheel cavity and the car wake vortex, affecting the aerodynamic drag of car and surface convective heat transfer of brake disc.[8]. The aerodynamic drag represents 20% of the total vehicle fuel consumption, while the drag contribution of wheel in total vehicle drag is around 25%.9. With the deep research on optimizing body shapes to reduce the vehicle aerodynamic drag in decades, there is a little space improving the body optimization.[10,11,12,13,14,15,16,17] So, the research on optimizing wheel structures to reduce the vehicle aerodynamic drag is increasing recently The wheel is the most important carrier and safety part in the car driving system, the lightweight extent and aerodynamic performance of which directly affect the car’s economy, power, ride comfort, braking and traffic safety.[1,2,3] At the same time, the brake disc is an important part for driving safety, heat fading of which will make the brake failure, while convective heat transfer accounts for 90% of the heat transfer of brake disc.[4,5,6,7] Rotating wheel will interfere with the flow field near
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