| The quality of power batteries is closely related to many performances of electric vehicles(such as cruising range,cycle life,economy and power),and is also the key to restricting the development of electric vehicles.Lithium-ion batteries have become the first choice of power batteries for electric vehicles with many advantages.However,the heat generated by lithium-ion batteries under extreme operating conditions will increase dramatically.If this heat is not discharged in time,the temperature of the battery pack will rise sharply.Once it exceeds the optimal operating temperature range(20℃-45℃),It is likely to cause serious consequences such as spontaneous combustion and explosion of the battery pack,which endanger the life safety of the driver.Therefore,an efficient thermal management system is of great significance to ensure the normal operation of lithium-ion batteries and improve the performance of electric vehicles.This paper proposes a hybrid thermal management scheme,which is based on the forced air-cooling scheme,and combines the high latent heat characteristics of phase change materials and the high thermal conductivity characteristics of thermal energy.First,by building a lithium ion battery test platform,the test data under different charging and discharging conditions were obtained,and the finite element software COMSOL was used to simulate the battery thermal model and heat generation rate model,and the battery heat Physical parameters.Then,an approximate modeling method based on multi-parameter decoupling technology is used to analyze the global sensitivity of the design parameters of the battery pack,effectively eliminating the design parameters that are not sensitive to the temperature performance of the battery pack.The coupling analysis results between the design parameters show that the difference of the coupling effect between physics parameters has little effect on the performance of the battery pack,indicating that different physics parameters can be analyzed independently.Compared with the commonly used parametric research methods,this method effectively reduces the dimension of the optimization problem and greatly reduces the optimization cost.Finally,the multi-objective particle swarm optimization algorithm is used to optimize the multi-objective design of the battery pack.The optimization results show that under high-rate discharge conditions,the operating temperature of the optimized battery pack does not exceed the optimal temperature range,but it still cannot meet the optimal temperature.The need for temperature uniformity.In order to solve the above defects,this paper comprehensively analyzes the influence of the location,number and size of air inlets and outlets on the heat dissipation performance of the battery pack,and improves the air inlet and outlet of the battery pack to determine the final design plan.Further reducing the maximum temperature of the battery pack,but the effect of improving the temperature unevenness is still not ideal.Therefore,through further research on the effects of different cooling air flow rates,different discharge rates,and high / low rate cycling charge and discharge processes on the heat dissipation performance of the battery pack,the simulation results show that under different discharge rates,the heat dissipation effect of the battery pack only Properly adjusting the flow rate of cooling air can meet the requirements,and becomes more and more obvious as the discharge rate increases;even in the continuous high rate charge and discharge cycle,the optimized battery pack can still maintain a good cooling effect.Finally,under different ambient temperature conditions,the heat dissipation performance of the battery pack is further analyzed,and the corresponding cooling scheme optimization strategy is proposed to enhance the applicability of the battery pack in the entire temperature range. |
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