Optimization Research On Energy Consumption Of Hybrid Vehicle Thermal Management System

With the rapid development of automobile industry and the depletion of renewable energy,improving the energy efficiency of vehicles has become the main goal of the automobile development stage.In this paper,based on the thermal system architecture of hybrid electric vehicle as the research background,the energy consumption of thermal system when the hybrid vehicle is working is studied,and combined with the thermal system working mode under high and low temperature conditions,the thermal management control strategy is proposed to further optimize the energy consumption of the vehicle thermal system.First of all,according to the selected type of hybrid vehicle,clarified the structure of vehicle thermal system,mastered the working principles of the air conditioning system,battery circulation system,motor and electronic components cooling system,engine cooling system and heating system,established the numerical model,confirmed the component parameters and based on the theoretical knowledge supports,the dynamic system and thermal system model of the vehicle were constructed by onedimensional simulation software.Secondly,achieved the operation control of thermal system model,the energy distribution strategy of hybrid electric vehicle was formulated,the speed and torque following of power system model was verified by NEDC working conditions,the component performance of air conditioning system was checked,the control mode of electronic expansion valve was optimized,and the cooling performance of air conditioning system was analyzed after the vehicle was exposed to the high temperature outdoors.Then,the balance performance of vehicle thermal system was verified,including the vehicle cooling performance under different speeds and high temperatures,as well as the vehicle heating performance under low temperature NEDC condition.The results showed that the temperature of vehicle thermal system components performed well under different high temperature conditions,and it rose faster under low temperature conditions,but the corresponding energy consumption of the vehicle cooling and heating energy was high.Further,the cooling time of the crew cabin and battery under different working conditions was obtained by changing the speed of the compressor and water circulating pump under different ambient temperatures and different vehicle speeds with the high temperature conditions.At the same time,observed the heat dissipation effect of the motor and engine after heating,and the analysis showed that the low speed of the motor and engine could meet the requirements.According to the cooling time of the crew cabin and the battery,selected the rotational speed and energy consumption of the compressor and battery circulating water pump which had the same time,the normalization algorithm was introduced,the cooling time and energy consumption were comprehensively considered by adding the weight coefficient,multiple fitting surfaces under different weight coefficients were obtained,and the fitting data of the best rotational speed was selected according to the standard deviation of the fitting data.Under the conditions different from the ambient temperature and vehicle speed in the above working conditions,generalization verification was carried out on the selected optimal speed fitting data,and the effectiveness of speed control strategy was verified by NEDC working conditions.The results showed that the error between the simulated value and the fitting value was small,and the fitting speed was suitable for various working conditions of the model.Then,two consecutive NEDC conditions were selected to explore the cooling time of the crew cabin and the battery at the ambient temperature of 30℃,35℃ and 40℃.The results showed that under the three ambient temperatures,the average cooling time of crew cabin and battery with the optimal rotational speed strategy had reduced by 14.7s and 194 s,the energy consumption of vehicle thermal system had reduced by 35.8%,12% and 6.1%.Finally,the low temperature heating energy consumption of vehicle thermal system was studied,and developed the cooperative control strategy of heating condition.According to the heat generation and demand of each subsystem,combined with the normal working temperature of components,the engine circulating water loop,battery cycling loop,motor electronic components cycling loop and warm air loop were connected.The vehicle thermal system shared a PTC,and each loop and PTC loop were connected by a valve,which controled the PTC range through different component temperatures and temperature differences.As the heating time increased,the component temperature interval was divided and the branch valve opening was controlled according to the different temperature interval.When the component temperature rose to a preset value,the branch water pump was shut down.The results showed that,when the valve opening and pump switch were not considered,the energy consumption would be effectively reduced by 22.2% compared with the independent heating of each component,and the collaborative thermal management of the interactive valve and pump switch could be further reduced by 16.7%.