Impact Of Exterior Shape Parameters On Aerodynamic Drag Of Electric Passenger Car

Faced with the pressure both from energy andenvironment, green energy has become a general trend in future.At the same time, promoting the new energy automotive industry has become the common strategic choice of world’s automobile enterprises. The target of promoting the new energy vehicles is to reduce environmental pollution, ease energy problems and raise the level of people’s life. Among them, the battery electric vehicles which make zero emission and no pollution are the best choice. But its development is still restriced seriously due to lots of problems, such as incomplete supporting facilities, short travel distance which hardly meets people’s daily needs. Reducing the aerodynamic drag through changing exterior shape parameters is regarded as a better way to extend travel distance, compared to increasing its own battery energy density. In this paper, electric passenger car is choosen to be analysised about the impact of changing exterior shape parameters. Due to the difference of power and transmission technology between battery electric vehicles and traditional vehicles, body struction changes a lot. So it is necessary to do autobody layout research again to study the impact which exterior shape paremeters do to electric passenger car aerodynamic drag, when facing new conditions and restricted factors.First of all, the main technical measures, distribution and function are summarized to discuss the advantages and disadvantages of different battery layout method. It is easy to draw a conclusion that there is larger aerodynamics research space when facing the new layout structure and the restricted conditions. Then numerical simulation is confirmed basing on automotive wind tunnel experimental data, and it will lay solid foundation to the rest research text. At the same time, exterior shape parameters impact on electric passenger car aerodynamic drag is arised through analysising aerodynamic characteristics in flow field.Based on both the aerodynamic research space of electric passenger car and exterior shape parameters which may impact to aerodynamic drag, low drag exterior shape is analysised in overall design. Seven parameters are chosen from the body on the transvese and longitudinal section curve control, then the optimal plan shows that the drag coefficient Cd is changed from 0.25883 to 0.23592, which decreased by 8.85%.In addition, aerodynamic global optimization research is carried on the low drag exterior shape. Eight parameters are chosen from the front, roof and rear, then the optimal plan shows that the the aerodynamic coefficient Cd * A is changed from 0.50793 to 0.48438, which decreased by 4.64%. In total, the Cd value was decreased by 13.58%, the Cd * A value was decreased by 13.13%.According to the numerious simulation and data, some conclusions were got:(1)There is a big space of electric passenger car in aerodynamic drag research, when facing the new layout structure and the restricted conditions.(2)In the period of low-drag exterior shape design, seven parameters were analysised. Among them, the variable length l1 do more than 50% contribution to the drag coefficient Cd, and height h1、 height h2、length l1、length 14、angle 2 do benefit to reduce it.(3)In the period of overall aerodynamic optimal design, eigβht parameters were analysised. Among them, the variable Middle_e and Middle_d do 80% contribution to the aerodynamic coefficient Cd * A.(4)Kringing approximate model is suitable for the method used in the paper, the R2 of the two is above 0.90.In conclusion, it is easy to figure out that it’s nesseary to do research on exterior shape parameters which will do impact on electric passenger car aerodynamic drag. With the effort in this paper, a low drag electric passenger c which Cd is 0.22369 is achieved, and the impact of several parameters is analysised during the analysis.