Study On Vehicle Integrated Thermal Management System Of A Front And Rear Wheel Independent Drive Type Electric SUV

As an energy-saving and environmental-friendly transportation,pure electric vehicles have received great attention by governments and automotive manufactures.As one of the hot topics,electric vehicle thermal management refers to maintain each part temperature of the vehicle within a reasonable range by an effective way,thus improving the security,economical and comfortable of the pure electric vehicles.Based on the cooperation project of our research group and enterprise,the objectives of this paper are to investigate the performance of integrated thermal management system of front and rear wheel independent drive type electric vehicle.The main contents of this paper are as follows:(1)Based on the characteristics of front and rear wheel independent drive type electric vehicle,a thermal management framework is designed,which can realize the functions of:power system cooling,battery pack preheating and cooling,cabin preheating and cooling and the waste heat recovery of the motors.And the specific realization forms of each function under different working modes are introduced.(2)In terms of power system cooling,in order to calculate the thermal load of the driving system,a bench test is designed to test the efficiency of driving motors and motor controllers.Based on the results of bench test,the heat generation models of driving motors and motor controllers are established respectively.The characteristics of the drive power consumption of the front and rear axle independently driven electric vehicles are analyzed,the torque distribution strategy of front and rear motors is established based on the highest efficiency of driving system.Then based on the torque distribution strategy,the cooling performances of the driving system are simulated under the vehicle driving cycles of low speed climbing,high speed climbing,maximum speed and HWFET.The results show that the driving cooling system achieves relatively good cooling capacity.(3)In terms of double evaporator air-conditioning system,firstly the theory analysis and study are developed.Then based on the theory and experimental data of air-conditioning system,the simulation models of compressor,expansion valve,heat exchanger and cabin are established.Meanwhile,the thermal management model of battery pack is established based on the test data of internal resistance and open circuit voltage.(4)Based on the environmental chamber,the air-conditioning system performance of the sample vehicle is studied experimentally.Firstly,the experimental conditions are established according to the industry standards.And the data related to the air-conditioning system are tested during the experiment.After data process and analysis,it is found that the air-conditioning system of the sample vehicle present some pitfalls.To solve these problems,a control strategy which consideration both cabin and battery pack cooling demands is put forward.Based on the strategy,the air-conditioning system is studied numerically,before the simulation,the model is calibrated and validated according to the test data.The simulation results show that,under the HWFET driving condition this control strategy can maintain the cabin temperature at about 24~oC and the battery pack temperature at 35-38~oC when the ambient temperature is 40~oC.(5)In terms of motors waste heat recovery,the simulation model and waste heat recovery strategies are established.The calculation results show that when the ambient temperature is-20~oC,under the driving condition of HWFET and WLTC,using the waste heat of motors to warm up the battery pack can reduce the PTC energy consumption 78%and 55%respectively.