Research On Low Aero-Drag Design Of Mid-Sized SUV On CFD

As the global car ownership continues to increase,environmental and energy issues are becoming more prominent.The car is mainly subjected to two external resistances,aerodynamic drag and rolling resistance.When the vehicle speed is increased to a certain extent,the proportion of aerodynamic drag in the total external resistance will increase sharply,resulting in a significant increase in fuel consumption of the vehicle.Therefore,by reducing the air resistance during the running of the vehicle,the fuel economy of the vehicle can be effectively improved.In order to improve the aerodynamic performance of the automobile,the automobile enterprises put lots of manpower,material resources and financial resources to test and study the aerodynamic characteristics of the vehicle.The traditional research methods of automobile aerodynamics,which are large,time-consuming and limited in resources,have been restricting the in-depth research of aerodynamics.In recent years,with the rapid development of large computing servers and researchers' continuous in-depth research on turbulence theory,computational fluid dynamics(CFD)has been widely used in automotive aerodynamics research and new vehicle development process.Uses the traditional research methods combined with the advance CFD simulation and research external aerodynamic,greatly improve vehicle aerodynamic performance,and improve the efficiency of research,and save the cost of research and development.This thesis is based on the basic theory of fluid mechanics.In the process of research,combined with previous project development process and optimization experience.Carry out the development of reducing wind resistance for a certain medium-sized SUV model,It contains the following:1.The simulation modeling and calculation of the vehicle external flow field are carried out for the target vehicle.By the calculating of base model,we can get the aerodynamic pressure field,velocity field,the pressure and velocity distribution of the car body.These calculations can be obtained for the later optimization scheme.2.According to the 3D data,the scale wind tunnel test model was made,and then the scale model was carried out wind tunnel test.The wind tunnel test results(scale model)and the simulation model calculation results were compared and analyzed to determine the simulation model that could be used for later optimization design.3.Study on aerodynamic drag reduction optimization schemes for exterior molding,car bottom and engine room.On the premise of meeting the constraints of vehicle product definition and general layout requirements: research on the aerodynamic drag reduction optimization scheme based on external modeling,including the optimization of the angle between the front windshield and the hood,and the optimization of the rear spoiler and the horizontal plane.The optimization of the rearview mirror mounting base and the optimization of the headlight shape,wherein the optimization of the rearview mirror and the headlights is realized by the hypermorph module in the Altair Hypermesh;the research is based on the drag reduction optimization scheme of the bottom of the car.Including the front and rear wheel chokes and bottom guards and other components to achieve the purpose of reducing the resistance;research based on the engine room and other parts of the drag reduction optimization program,including the radiator grille opening area,radiator sealing plate and other components to achieve resistance reduction purpose.The wind resistance of the vehicle test was reduced from 0.404 to 0.369,which reduced by 8.6% and reached the initial goal of the project.Combined with the final result of the wind tunnel test,the actual contribution of each local optimization scheme to reduce the aerodynamic drag of the vehicle is compared and verified.Finally,the EGO global optimization algorithm is used to optimize the front and rear wheel chokes,which reduces 4count.The practicality of the EGO optimization algorithm in the development of aerodynamic drag reduction of the whole vehicle is fully verified.The middle-sized SUV models are summarized in the aerodynamic drag reduction process of the whole vehicle and a certain regular experience(including optimization process,etc.),paving the way for future high-precision vehicle performance development.