Reliability Design Optimization Of Power Battery Pack Structure In Multi Physical Field

With the increasing environmental problems and energy shortage,the development of electric vehicles has been strongly supported by the government and society.The core component of the electric vehicle is the power battery pack.The power battery pack faces the thermal and mechanical physical fields under normal driving conditions.Therefore,it is very necessary to study the structure of the power battery pack to ensure that the energy system is in a suitable working environment,which is of great significance to ensure the safety and reliability of the electric vehicle.In this paper,the structure of the power battery pack under multi physical fields is studied and optimized.The structure of the battery pack can be logically divided into heat dissipation structure(i.e.commonly described thermal management system)and mechanical structure,which correspond to the thermal physical field and mechanical physical field respectively.This paper mainly starts from these two aspects,and the details are as follows:1.Research on the heat dissipation structure of the power battery pack:according to the internal environment of the power battery pack and the temperature characteristics of the battery,a heat dissipation structure based on a new channel liquid cooling plate is proposed.Taking multi row square lithium-ion batteries as the research object,the Bernardi heat generation rate model is used for reference,and the CFD simulation model of the cooling structure of liquid cooled lithium-ion batteries is established by using the Flotherm finite element analysis software.The performance of the cooling structure is studied by adjusting the structural parameters of the liquid cooling plate and the flow rate of the coolant.Finally,taking the maximum temperature and the maximum temperature difference of the battery module as the reliability constraints,and taking the minimum mass of the liquid cooling plate in the cooling structure as the optimization objective,the optimization design is carried out.The mass of the liquid cooling plate is reduced from 1.828kg to 0.832kg.The results show that the heat dissipation structure has enough heat dissipation capacity,and its temperature consistency is excellent.The maximum temperature difference can be reduced to 1.0? in the limit state.When the coolant flow rate is fixed,the maximum channel spacing of the liquid cooling plate is 26mm,and the width of the rectangular channel is about 7mm,the heat dissipation performance of the heat dissipation structure is the best2.Research on the mechanical structure of the power battery pack:according to the actual mechanical structure of the power battery pack,the pre-processing model of the battery pack including the quality points of the battery modules and electrical components is established.Finite element analysis is carried out for the six modes of the battery pack mechanical structure under the actual constraint state,and the impact load of the battery pack mechanical structure under three limit conditions is analyzed by finite element method,all of which meet the use requirements;random vibration fatigue analysis is carried out for the battery pack mechanical structure,and the results show that the strength of the lower box and the lifting lug needs to be improved.Finally,the following fatigue strength of the box and the lifting lug is a reliability constraint problem,and its minimum mass is taken as the optimization objective to carry out the optimization design.The mass is reduced from 41.24kg to 37.91kg.The research results show that the mechanical structure which meets the requirements under the limit working condition may also have fatigue damage.By reasonable distribution of the structural parameters of the lower box and the lifting lug,the overall quality can be reduced while the fatigue life is guaranteed.