Design And Analysis Optimization Of Air Cooling And Heat Dissipation Of FSEC Racing Car Power Battery

With the aggravation of energy consumption and the increasingly prominent pollution problem,in order to respond to the national strategy of new energy vehicles and cultivate more talents in this industry for the country,China Society of Automotive Engineering began to hold the first Formula Student Electric China(FSEC)competition in 2013.At present,the competition has been developed to nearly 80 colleges and universities in the country,and is gradually popular in colleges and universities around the world.The fierce competition and the severity of the racing condition have put forward high requirements for the reliability of the racing power system designed by universities.Meanwhile,the rules of the competition also make the design of the battery cooling system more important.In this paper,the electric racing car of Xingzhi Team of North University of China is taken as the research object,and the heat dissipation of the power system composed of nickel-cobalt-manganate lithium battery used in the racing car is studied,so that the heat generated by the racing car battery during the working period can be dissipated in time,and the battery pack can always work in a reasonable temperature range,so as to improve the service life of the battery and the safety of the racing car.Firstly,starting with the composition structure of lithium-ion battery,the working principle is introduced.According to the heat generation mechanism of battery,the source of the heat generation of battery is defined.The thermal model of single battery and the simplified Bernardi heat generation rate model are established,and the thermal physical property parameters such as battery density,specific heat capacity and thermal conductivity are equivalent treated according to the calculation and specification.Secondly,based on the event,the single battery was set into two working conditions of short-time discharge with large current and long-time discharge with small current,and the thermal effect of single battery under the two working conditions was studied.The corresponding temperature rise experiment and HPPC experiment platform were built,and the relationship between battery heat generation rate and discharge time was successfully obtained by using the experimental data and compiled into UDF.The three-dimensional model of single battery was generated by using CATIA and thermal simulation analysis was done in Fluent.The simulation data and temperature rise experiment data were compared and analyzed,and the results showed that the maximum temperature rise error was 0.5℃.The maximum error of temperature difference is 0.12℃,which confirms the feasibility of single cell thermal model.Then,according to the selected motor,the connection mode,the number of cells and the energy of the battery Pack were established.Combined with the competition conditions and Newton’s cooling law formula,the heat dissipation of the battery box was determined at 4.83m~3/min.Two suitable cooling fans were selected,and preliminary modeling and reasonable arrangement were made for the battery system module and other electrical components in the box.The three-dimensional structure of the battery box cooling system is preliminarily completed.Finally,the preliminary thermal simulation of the simplified battery system is done,and the calculation parameters are set and the heat dissipation factors are determined.On this basis,the orthogonal test method was selected to optimize the battery heat dissipation system.Finally,the optimal scheme was determined among the three optimization schemes,and the simulation analysis was carried out for the endurance race condition of FSEC competition project.The results show that the maximum temperature of the ultimate discharge condition of the optimal scheme is 33.37℃,and the maximum temperature difference is 3.87℃,which is nearly 33%better than the preliminary thermal simulation.In order to reduce the power consumption of the low pressure system of the racing car,the heat dissipation efficiency of the two-fan model was analyzed based on the optimal scheme,and it was found that the heat dissipation effect of the two-fan model was better,which was optimized by nearly 27%compared with the preliminary thermal simulation.The assembled battery box was tested in the vehicle and results show that the heat dissipation effect is good and it is in the specified temperature range of the battery work,which lays a foundation for the later temperature rise experiment of the real car.