| Today,the total car ownership continues to grow and fossil energy is gradually decreasing,development of new energy vehicles has become a key area of concern for countries and major automobile companies.As the main energy source of electric vehicles,the performance of power batteries directly affects the performance of complete vehicles.There are many types of electric vehicle power batteries.The power battery selected in this paper is a lithium-ion battery.Due to the mechanism of the lithium ion battery,a large amount of heat will be generated during it works,and an excessive temperature will reduce the performance of lithium ion battery.Therefore,when the temperature of the lithium ion battery pack reaches the warning line,certain heat dissipation measures must be taken to reduce the temperature of the lithium ion battery.Firstly,this paper introduces the research background and significance of battery thermal management system,gives the types and characteristics of commonly used power batteries,and introduces the research status of battery thermal management system at home and abroad.Secondly introduce the structure and chemical principle of lithium-ion battery,give the heat generation model of lithium-ion battery,and according to the temperature variation curve of single-cell lithium-ion battery at 1C-rate,and calculate heating power of single-cell lithium-ion battery at the 1C-rate,the heating power is 4W.Then,the thermal characteristics experiment and thermal simulation of the air-cooled battery pack were carried out.Firstly,three complete 1C-rate charge and discharge cycles were performed on the lithium ion battery pack.The temperature tester was used to record the battery pack to indicate the temperature change,and the surface temperature of the battery pack was plotted over time after the experiment.Then,the thermal simulation of the thermal characteristics of the air-cooled battery pack is carried out,and compared with the experimental results.It is concluded that the simulation results of the thermal characteristics of the air-cooled battery pack are basically consistent with the experiment,indicating that the boundary condition of the battery pack thermal simulation is reasonable;Simulation and experimental results show that the temperature changes too much when the battery pack is running under natural cooling.The maximum temperature and maximum temperature differenceexceed the safe operation requirements of the battery pack.Additional cooling measures must be taken to ensure the safe operation of the battery pack.Finally,based on the battery pack structure and cooling requirements,the battery pack thermal management system is designed.The piezoresistive calculation is carried out on the thermal management system.According to the simulation results,the waterway structure is optimized,the water pressure resistance is reduced,and the total pressure drop is reduced.Then,using the water-optimized thermal management system and the battery pack,the fluid-solid coupling thermal simulation was carried out.Through simulation calculation,it was found that the graphite material heat-conducting plate is beneficial to balance different single cells due to its anisotropy compared with the aluminum alloy heat-conducting plate.The temperature between the two can effectively reduce the temperature difference of the battery pack.A battery pack heating fluid-solid coupling thermal simulation was carried out on the designed battery thermal management system.The results show that the battery thermal management system can quickly heat the battery so that the battery can operate within the specified working range.And it could ensure the battery pack temperature difference is within a certain range. |
PDF Full Text Request