Study On Aerodynamic Characteristics Of Passenger Car Based On Shape Of Front Grille

With the increase of car ownership and speed, the decline in energy storage and theimprovement of people’s requirements, automotive aerodynamics research has attractedmore and more attention of the automobile manufacturers. As the only entrance of theunder-hood except the underbody, automobile front grille shape, position, openarea, diversion direction and density have important effect on the intake airquantity and flow field distribution in the car. On the one hand, the aerodynamicdrag rises due to the consumption of the air kinetic energy, on the other hand, the enginecompartment temperature decreases due to the heat exchange between the flow and thecooling module, which improves the engine compartment environment. In order to solve thecontradiction above, the shape of automobile front grille must be reasonably designed.In this paper, cross-flow radiator with water inlet and water outlet on the same side wasused. In order to make the simulation results consistent with the actual radiator, partition wasset in the middle of the main radiator body and the cooling liquid inlet and outlet pipe toensure that the fluid flow route is U shape inside the radiator.Firstly, the passenger car model with cooling fans still was simulated to research theapplicability of four kinds of turbulence models in STAR CCM+. Compared with the testresults from the enterprise, Realizable k-e model was selected for subsequent numericalsimulations. The simulation method was verified by the grid Y+value near the body. Afterchoosing the simulation method, the base car model was simulated to get the aerodynamicdrag coefficient Cd value and the radiator air mass flow Q value. Then the flow field and thetemperature field is analyzed in detail. The front grille shape mentioned in this paper mainlyincludes two aspects: grid parameters and grille forms. In the study of grid size, orthogonalexperimental design method was used to arrange the simulation scheme firstly.Then simulations and analyses were carried out to obtain the optimal scheme of Cd value(A5B5C5) and the optimal scheme of Q value (A1B2C1). Finally the engine compartment flow field and temperature field were analyzed in the two groups of optimum scheme, and theinfluence rules of different grid parameters on vehicle aerodynamic characteristicsand under-hood heat dissipation characteristics were obtained. For the study of grille forms,four grille forms which are different from the prototype were designed, including Straighttype, Concave type, M type and W type. Then these models were simulated and the resultswere analyzed, including quantitative analysis and qualitative analysis, the influence rules ofdifferent grille forms on vehicle aerodynamic characteristics and under-hood heatdissipation characteristics were obtained.