Research On Coupling Optimization Of Car-Body Drag Reduction And Battery Heat Dissipation Of Pure Electric Vehicles

In the background of environment and energy crisis, the development of typically pure electric vehicles for new energy vehicles have become the inevitable course in the development of automotive industry.However, insufficient mileage has become one of the bottleneck problems of pure electric vehicle technology development. Reduce body aerodynamic drag and improve the battery energy conversion efficiency is an effective method to improve the mileage of pure electric vehicles. But the existing pure electric vehicle body did not make full use of the advantages of its simple structure and flexible arrangement of battery pack. Usually following the traditional fuel automobile styling which with large air drag coefficient. On the other hand, in the research of battery pack cooling, the influence of car body structure, the location and structure characteristics of the battery pack on the battery pack air flow cooling characteristics has not been systematically considered.What’s more,there isbasically littleresearch of optimization of automobile inner and outer flow that considering the aerodynamic reduction and improve the battery pack cooling performance.This paper take a pure electric vehicle as research object, through proper structure design of battery pack to ensure the battery work in the optimum temperature range and enhance the discharge efficiency. Thenreduce the drag coefficient to saving the battery power of the target model based on the characteristics that pure electric vehiclehas less transmission components and the structure is relatively simple. Finally, coupling the battery temperature control and vehicle drag reducing, obtaineda comprehensive optimal models with low body resistance and good heat dissipation performance of battery pack. The concrete research contents are as follows:1. The grid quality of the finite volume method and thermal physical model has an important impact on the simulation of the external flow field and body battery temperature field results.Therefore, must first to determine the simulation method in this paper. By comparing the experimental results with the model wind tunnel,investigates theinfluence of aspect ratio, skew, minimum angle etc.mesh quality evaluation criteria on the precision of car-body outflow calculation, select the comprehensive evaluation indicators to evaluate the grid and finally improved mesh quality and flow field calculation accuracy;Using the Bernardi battery heat generation theory and DO radiation model to establish the single battery heat generation model.Compared with the previous experimental results, the accuracy of battery heat generation model is verifiedand determined the simulation scheme.2.In order to guarantee the optimal working temperature of the battery pack,the battery cooling and insulation performance under different layout conditionresearch is carried on. The temperature field of three different arrangement condition, cabin layout, chassis layout and spare tiregroove layout were calculated, andcompared with the real vehicle road test, put forward heat dissipation improvement schemeand insulation measures of the battery pack under different arrangement conditions.3. Using the feature transplantation method to study the drag reduction of research object. Considering the battery packet collision safety, battery temperature field condition and car-body shape improved space, the battery pack arranged between the chassis and the crew cabin is more appropriate.Through using the feature transplantation method,remove the body attachment, add a rear wheel cover, flat the front etc., the drag coefficient decreased maximumby 23.2%.4.According to the field synergy theory, a double field coupling optimization of the target models was conducted.Select the head length, tail departure angle, rear air window angle, air inlet grille size, inlet size of battery pack and spacing of cooling fan etc. 9 design factors. Using optimal Latin hypercube method to obtain sample points, established high precision RSM agent model,adopt Multi-Island genetic algorithm obtained thetheory optimal models.Use field synergy principle to analysis the angle between the state of temperature gradient and heat flow vector, reveals the low and high temperature regions distribution causes on the battery surface.Eventually, restore the theory optimal models for vehicle models and carries on the numerical calculation. Results shows that drag coefficient decreased 21.97%, the highest temperature of battery group dropped 2.44℃, a decline of 5.5%.