Theoretical And Numerical Analysis On The External Flow Of Electric Vehicles

Compared with the conventional cars, the external structure of electric vehicle isalmost the same except for its difference power systems, in terms of the research andanalysis of aerodynamic contour for electric vehicles shape, the methods and theoriesused in conventional car can be made into considered, for example, the wind tunneltesting and the numerical simulation method. In this paper, the external flow of aelectric vehicle—LF320, which comes from the innovation of science and technologycommission of Shenzhen municipality—lightweight composite materials design andsimulation of micro-electric car, will be calculated by using the numerical simulationmethod.For the theory aspect, according to the basic theory of the fluid flow and taking theassumption of thermostat, three-dimensional incompressible flow field intoconsideration, the mathematic model for the numerical simulation—the basic controlequation, the turbulent control equation and the solve method and process of thevelocity and pressure are deduced in detail.And then, on the aspect of numerical calculation, in order to validate and illustratethe reliability and accuracy of the numerical simulation method in the study andanalysis of the external flow around the car, a international model—MIRANOTCBACK CAR is selected, meanwhile, it is also used to present the process andmethods of numerical simulation in detail. Using RNG k-ε model to simulate theexternal flow of car body, that the relevant body aerodynamic drag and lift values areobtained by calculating at different inlet velocity，then calculate the correspondingcoefficients through its formula, by comparing the results of the numerical simulation tothe wind tunnel test, the result shows that the numerical method can also get a good andcredible outcome. So, on this basis, using the same method to simulate the external flowaround the electric vehicle—LF320, calculating its aerodynamic drag and lift, studyingits flow velocity distribution and the pressure distribution characteristics of the externalflow field.In consideration of the energy saving, it is widely considered that the way toreduce the body’s aerodynamic drag is the most effective and economic, so based on the drag, introduce the local iteration optimization method, by modifying the main featuresof the tail to the body shape—the rear window angel, the side angel and the departureangel. Taking the actual situation into account, change the values of the selected shapewith a range of parameter values, after that, Create different vehicle models and analyzeall the rebuilt car models by Numerical simulation reanalysis, studying the relationshipbetween the local body shape and aerodynamic drag. By this way, getting the optimalparameter value and then rebuild model for further analytical validation, from the resultof calculation, it presents that the optimal model has the better aerodynamicperformance, its aerodynamic drag decreases obviously. Finally, the paper analyzes theimpact to aerodynamic drag by installing different rear spoiler，it’s also show thatdifferent rear spoiler has a certain impact on the aerodynamic drag.