Study On Thermal Management Of Lithium Titanate Battery For Tram

The lithium titanate battery has excellent charging,discharging efficiency,high energy density and high safety,so it has become one of the first energy storage options on trams.However,in the face of the operating characteristics of trams with high traction power,high braking power,and frequent and large fluctuations in operating conditions,lithium titanate batteries not only produce a large amount of heat,but also have difficulty in dissipating heat under the conditions of lightweight vehicles and space constraints,the excessive temperature rise,which seriously affects the performance and life of the battery.Therefore,on the basis of theoretical analysis,a combination of simulation and experiment methods is used to study the temperature distribution characteristics of lithium titanate batteries under different operating conditions.Based on this,a liquid cooling/phase change material composite heat management method was designed,and compared with the two single heat management methods of natural cooling and liquid cooling,result show that the composite thermal management method can make the battery work in a suitable temperature range and the internal temperature difference is small,so it has a better temperature control effect.The main research contents and conclusions are as follows:（1）For specific lines and trains,through simulation calculation obtain the current conditions of the lithium titanate battery corresponding to the typical operating conditions of the tram,provide working condition parameters for the electric-thermal coupling finite element analysis and experiment of lithium titanate battery later.（2）Propose a liquid-cooled/phase change material composite cooling lithium titanate battery thermal management program.Determine the structure of the liquid cooling system according to the arrangement of the battery cells and the size of the battery module,and design the geometric model of the liquid cooling plate.Compare the advantages and disadvantages of different phase change materials,determine the phase change materials to be used in this article,and make theoretical calculations on the quality of phase change materials,and design the size and position of the phase change materials according to the battery module space limitations.（3）Establish a lithium titanate battery electric-thermal coupling model,carry out simulation calculation base on COMSOL,and comprehensively analyze the temperature distribution of the battery module at an ambient temperature of 25°C and a working current.The heat dissipation performance and uniform temperature performance of the three thermal management methods of natural cooling,liquid cooling,and liquid cooling/phase change material composite cooling are successively enhanced.,and when the battery module adopts liquid cooling/insulating phase change plate composite cooling,the maximum temperature T_max=30.2℃and the maximum temperature differenceΔT_max=4.8℃.（4）Build a thermal management experiment platform for lithium titanate batteries.Combining the economical and lightweight principles of the energy storage system of trams,the influence of phase change materials on the temperature of battery modules is analyzed through experiments,and a phase change material structure with differentiated thickness splicing is designed,Through comparative experimental research on natural cooling,liquid cooling,phase change material cooling and liquid cooling/phase change material composite cooling,the temperature characteristics of the battery module under different ambient temperatures and current cycles under different working conditions are analyzed.The results show that the combined thermal management method of liquid cooling/insulating phase change plate can make the T_max of the battery module under the current cycle of the working condition less than 50°C,andΔT_max less than 2.3°C,comprehensively considering the heat dissipation,temperature uniformity and economy of the energy storage system,the liquid cooling/insulating phase change plate composite cooling has the best engineering practicability and is the best thermal management method.