| More than one million minibus were sold in 2007, and the increase ratio of sale will be over 10% every year by estimation. Along with the development of automobile technique and freeway, the practical speed of minibus will be higher, and it will cause fuel consumption increment. In order to improve transportation efficiency, the aerodynamic characteristics of minibus will be put more attention.Computational fluid dynamics is used in the development process of automobile more and more. In this dissertation fundamental theory of computational fluid dynamics and two equations turbulence model which include standard k ?εmodel, RNG k ?εmodel and LES model are introduced in short, then apply these three models to simulate the Ahmed blunt body and compare the results with the experimental results. By analyzing, LES model is more accurate than other two models; however since it is uneconomical in computing resource, it will not be widely used in practical project. Synthetically considering all above aspects, RNG k ?εmodel is used in this dissertation.Basing on the three dimensional CAD model, CFD computing grid is established. Software called CFX is conducted to simulate the external flow-field. Through analyzing flow pattern of external flow-field in detail, the relationship among flow theory, flow character and aerodynamic drag force around the mini passenger car is investigated and the reason why the drag force is produced is clear. According to the issue existing in the external flow-field, corresponding optimization solutions are proposed. In addition, the fuel economy after optimizing is calculated, the result demonstrates that fuel saves 9.92%.Before analyzing dispersion management in the engine room, the entry grid of engine room is optimized. On the basis of the optimization, temperature field and velocity field is calculated, and several important parameters about radiator are obtained. That provides important evidences for matching vehicle cooling system. |
PDF Full Text Request