Study On Aerodynamic Drag Reduction Of Heavy Commercial Vehicle Shape In The Styling Phase

In recent years,with the development of high-grade highways and the rising oil prices in China,the pressure of long-distance transportation of heavy commercial vehicles is increasing.Low wind resistance and low fuel consumption will become the objective requirements and development trend of heavy commercial vehicles.The shape of heavy commercial vehicle has the characteristics of large windward area and drastic transition at the rear of the container,which seriously affects the aerodynamic characteristics of the vehicle.On the one hand,the aerodynamic drag of the heavy commercial vehicle is larger,on the other hand,the stability of the vehicle under cross-wind condition is reduced,which affects the driving safety.In order to improve the fuel economy and driving safety of heavy commercial vehicles,the parametric optimization design of CAS model for heavy commercial vehicles at the initial stage of modeling is carried out,and the influence of shape parameters of heavy commercial vehicles on the aerodynamic characteristics of the vehicle is further studied.Firstly,this paper summarizes the development status of drag reduction of heavy commercial vehicles and the aerodynamic optimization methods of vehicles,and discusses the drag reduction space and mechanism of heavy commercial vehicles.In this paper,GTS standard model is selected as the object of study,combined with CFD numerical simulation and vehicle wind tunnel test,the number of grids,turbulence model and simulation settings of vehicle numerical simulation are validated.Comparing the simulation results with the model wind tunnel test data,the minimum error between the simulation and the test results is 0.79%,which meets the requirements.Thus,the parameters of external flow field simulation for heavy commercial vehicles are determined,which lays the foundation for CFD numerical simulation research in this paper.In the early stage of heavy commercial vehicle modelling,combining modelling and aerodynamics to complete the modelling design,the CAS model in the modelling stage is used as the initial model for simulation optimization,and the aerodynamic characteristics of the initial model external flow field are analyzed.Combined with pressure nephogram and turbulent kinetic energy nephogram,the key parts which have great influence on the aerodynamic characteristics of the initial model vehicle are put forward,and the overall parametric optimization of the heavy commercial vehicle shape is carried out based on seven key parts.In order to reduce the streamlined coefficient Cd*A of the initial model,40 sets of sample points were generated by combining Sculptor and Star-CCM+software with Isight platform based on the optimized Latin hypercube experimental design for simulation,and optimized by Kriging approximation model and ASA adaptive simulated annealing optimization algorithm.The results show that the streamline coefficient of the optimized CAS model is reduced by 4.31%,and the obvious optimization effect is achieved.In order to further explore and optimize the drag reduction space of heavy commercial vehicles,on the basis of overall optimization,body accessories such as diversion plate,side skirt and trunk tail plate are added based on the optimization model,and further parameterized aerodynamic optimization of the optimization model for adding body accessories is carried out to complete the comparative analysis of aerodynamic characteristics of different vehicle forms.The results show that the streamlined coefficient of the optimized vehicle is 13.42% lower than that of the original model,and the drag reduction effect of the optimized vehicle is obvious.Finally,the aerodynamic characteristics of four different vehicle types under 6 angle crosswind conditions are compared and analyzed,and the effects of crosswind on the aerodynamic characteristics of the vehicle and the optimization effect of the vehicle are deeply explored.The results show that the model with aerodynamic accessories has better aerodynamic characteristics under cross-wind conditions,and the lateral force coefficient of the optimized model_accessories decreases the most than that of the initial model,reaching 14.51%,so it has better cross-wind stability.In summary,this paper studies the parametric optimization of CAS model of heavy commercial vehicle in the early stage of modeling by using Isight optimization platform.The overall optimization of the vehicle and the local optimization of accessories have achieved obvious drag reduction effect.At the same time,it is helpful to pave the way for the study of the influence of the shape parameterization method and shape design variables on the aerodynamic characteristics of heavy commercial vehicles.