| Battery is the heart of electric vehicle,and the key to the development of new energy vehicle industry.Lithium-ion battery is widely applied because of its high energy density and excellent performance.However,the performance,life and safety of lithium-ion battery depend largely on it's working temperature.in order to ensure the performance,life and safety of the lithium battery in the complex and changeable driving conditions of the electric vehicle,it should work at a suitable working temperature.as the control system of battery temperature,battery thermal management system(BTMS)play an important role in protection of output power,service life and thermal safety of power battery under harsh conditions,such as high temperature environment,low temperature,high rate discharge operating mode.therefore,the performance of the battery heat management system is very important to the power output and service life of the power battery.This paper studies the calculation method of heat generation in engineering application,and selects appropriate thermal management evaluation conditions by comparing different cycle operating modes to accurately evaluate whether thermal management design can meet battery performance requirements.And use commercial CFD software(star ccm+)to analyze the flow field and temperature field of the heat management system,and optimize the design of the cooling plate according to the results of the analysis.The specific research contents are as follows:(1)this paper expounds the significance of studying BTMS,and systematically summarizes the current research status and shortcomings of the BTMS.Through benchmarking BTMS scheme of typical vehicles and analysising the development direction of the battery system,the liquid cooling BTMS has gradually become the mainstream development trend.(2)by analysising the working principle of lithium ion battery and its heat transfer and heat generation models,identify the parameters required for the calculation of heat generation,these parameters include open circuit voltage(OCV),internal resistance(R)and current(I)under driving condition.Based on the HPPC test,the data of OCV and internal resistance under different SOC are obtained.collect the commonly used urban driving cycles both home and abroad,by comparing the required RMS currents of different driving cycles,US06 is selected as the evaluation driving cycle of BTMS.(3)based on the boundary of battery,the battery system scheme was designed and the themogenesis of the battery system under the US06 driving cycle was calculated.The BTMS sheme is selected based on the battery themogenesis.the cooling plates and internal flow-path are designed to ensure that the temperature of the system is uniform.Meanwhile,a heating system scheme is designed to provide a reference for PTC selection.(4)Using the commercial CFD analysis software star ccm+ to establish the simulation model of the thermal management system.First by analyze the stream field of the flow-path,get the pressure drop of the flow path under different flow rates and determine the maximum flow rate of the cooling system.Then,the temperature field of the BTMS is simulated and analyzed.the results show that the highest cell temperature is 35.70? and the minimum core temperature is 31.85?when the single core has an average heat generation power of 3.29 w.The maximum temperature difference of the core is 2.11?,which meets the design requirements.(5)Trial produce the prototype of the power battery system,and design the verification test of the thermal management system.under the US06 driving cycle,the maximum temperature of the battery is 38? and the maximum temperature difference is 5?,which achieve the design goal.then the calibration test of the BMS is designed to calibrate the cooling flow,the inlet temperature of the coolant and the cooling opening temperature. |
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