Simulation And Experimental Study On Thermal Management System Of New Electric Vehicle Based On Heat Pump Air Conditioning

Efficient and reasonable thermal management system of electric vehicles can reduce energy consumption,avoid energy waste,improve battery life,and increase the sustained mileage of pure electric vehicles,which is of great significance for promoting the development of pure electric vehicles.Therefore,based on heat pump air conditioning technology and combined with motor heat dissipation,waste heat recovery and power battery heating heat dissipation,this paper proposes a new type of electric vehicle thermal management system,and conducts research through simulation and experiment.The main research contents and results are as follows:(1)Combined with the heat pump air conditioning system,motor heat dissipation and waste heat recovery system and power battery heating and heat dissipation system,a new thermal management system scheme of electric vehicle is designed.The thermal management system scheme can not only realize the temperature control of passenger cabin,motor and power battery,but also can recycle the waste heat of motor.From the analysis of structure and principle,the thermal management system scheme can ensure the performance of electric vehicle and effectively reduce the energy consumption of electric vehicle.(2)Based on a electric vehicle model,the thermal load of its passenger cabin is calculated under the ambient temperature of-10℃,and the conclusion is drawn that over 3900 W of heat is needed to maintain the temperature of the passenger cabin at 24℃.So choose in the heat pump air conditioning system displacement compressor for 32 ml/r,and according to the parameters of the compressor corresponding heat pump air conditioning system model simulation is established,then the simulation results were compared with the experimental results concluded that heat pump air conditioning system in the compressor suction exhaust temperature of the suction or discharge temperature,condenser and evaporator vacuum exhaust temperature changes of the simulation curve with the experimental curve,error range within3 ℃.Then the simulation models of the motor system and the power battery system were established respectively.By comparing the simulation results with the experimental results,it was found that the motor model could well simulate the thermal characteristics of the motor,and the experimental temperature rise error would not exceed 3℃.The quasi-static battery model can well simulate the thermal characteristics of the battery,and the experimental temperature rise error will not exceed 1℃.(3)According to the new thermal management system scheme,the corresponding vehicle thermal management system control strategy is designed.The control strategies are divided into passenger cabin thermal management control,motor thermal management control,power battery thermal management control and heat pump air conditioning evaporator defrosting logic.According to the logic threshold control,they are divided into different working modes.The temperature control of passenger cabin adopts the fuzzy adaptive PID(Proportion Integration Differentiation,PID)control with high control precision,and the temperature control of motor and battery adopts the fuzzy control.(4)Using Visual Studio C++ compiler combines simulation model and controller.The simulation model was established based on AMESim software and the controller is built based on MATLAB/Simulink software.Then the performance of heat pump air conditioning,motor waste heat recovery and power battery heating and heat dissipation were simulated and analyzed respectively.The simulation results show that in the single heating mode of the heat pump air conditioner,when the ambient temperature is greater than 0℃,the heating energy efficiency ratio of the air conditioning system is basically maintained at 2～4,and when the ambient temperature is lower than 0℃,the heating energy efficiency ratio of the air conditioning system is less than 2,and the economy of the air conditioning system decreases greatly.In the mode of heating passenger cabin with motor waste heat alone,the heating requirements of passenger cabin can be met when the ambient temperature is greater than 10℃.In the mode of passenger cabin heating with motor waste heat pump air conditioning,the passenger cabin heating demand can be met when the ambient temperature is greater than-10℃.And the equivalent heating energy efficiency ratio of the air conditioning system can reach 25.94 when the passenger cabin demand temperature is 24℃ and the ambient temperature is 0℃,and can still reach 3.92 when the passenger cabin demand temperature is 30℃ and the ambient temperature is-10℃,which shows good energy saving effect.In the working condition of ambient temperature above 5℃,motor waste heat can quickly and effectively heat the power battery.In the working condition of ambient temperature below 5℃,additional PTC(Positive Temperature Coefficient,PTC)heater needs to be turned on to heat the battery pack quickly.When the temperature of the power battery reaches 40℃,the temperature of the battery pack is maintained between 31℃～40℃ and tends to 35℃ when the heat dissipation mode is opened at different ambient temperatures and discharge rate,which can meet the design requirements of the power battery heat dissipation system.The new electric vehicle thermal management system proposed in this paper has been proved by simulation and experiment that it can effectively reduce system energy consumption while ensuring vehicle performance.The scheme is novel and has great practical value,which provides part of theoretical reference for promoting the development of electric vehicle thermal management system.