Research On Thermal Management Of HEV Power Battery Based On Engine Waste Heat

In recent years,with the development of new energy vehicles,the automotive industry’s requirements for the energy consumption and environmental protection of new energy vehicles have become increasingly strict.How to reduce the energy consumption of new energy vehicles has become an important development direction in the future.As an important driving energy source for hybrid vehicles,power batteries need to consume a part of the vehicle’s energy consumption during thermal management.Relevant research shows that only one third of the energy produced by the combustion of engine fuel is effectively used,and the remaining energy is discharged into the environment in the form of thermal energy.Use exhaust heat to drive a potential and environmentally-friendly adsorption refrigeration system,and apply the amount of cold generated to the thermal management of power batteries in hybrid vehicles to improve the working efficiency and performance of power batteries and extend their use.At the same time of life,it is also of great significance to reduce the energy consumption and exhaust emissions of hybrid vehicles.In this paper,in order to solve the problems of exhaust hybrid heat generated by the engine cannot be fully utilized during the running of a parallel hybrid vehicle,and the energy consumption of the thermal management of the compressor-type power battery is relatively high.This paper designs a power battery thermal management system based on engine waste heat,and studies the heat dissipation effect and low temperature preheating effect of the battery thermal management system.The main research contents and conclusions of this article are as follows:(1)Design the thermal management system of hybrid vehicle power battery based on engine exhaust heat,elaborate the working principle of battery thermal management system based on adsorption refrigeration,and set up the mathematical model of adsorption refrigeration system.The main device parameters such as adsorption bed,condenser and evaporator are designed in detail.(2)Select a parallel hybrid vehicle simulation model,use fuzzy drive control strategy and lithium iron phosphate battery pack,and use the vehicle performance simulation software ADVISOR2002 to obtain the power battery charge and discharge under a cyclic operating condition composed of 4 high-speed operating conditions.Current information and engine operating data,the results show that the main range of engine speed under cycle conditions is 1000r/min～3000r/min;Based on this,through the engine performance simulation software AVL BOOST,the exhaust temperature range of the engine in the main speed range is 650K～879K,exhaust flow rate range 0.03kg/s～0.08kg/s;Then use EES software to simulate and analyze the refrigeration characteristics of the designed adsorption refrigeration system,it was found that with the increase of engine exhaust temperature and flow rate,the cooling capacity shows an increasing trend,which can reach a maximum of 3.15kW,the refrigeration power(SCP)per unit mass of the adsorbent is 171W/kg,and the cooling performance coefficient(COP)of the system is 0.354.The change of cooling capacity with time at three speeds of 1000 r/min,2000 r/min and 3000 r/min was obtained.(3)The real-time temperature rise and other physical parameters of the selected lithium iron phosphate battery pack under cyclic conditions were determined through tests,and a temperature rise test bench for the power battery pack was built.The incubator is used to simulate the ambient temperature,and the battery is placed in the incubator.The obtained current information is input into the power battery charge-discharge test system as a known condition to simulate the actual charge and discharge of the power battery in the actual operation of the car,and the temperature rise of the battery is measured with an infrared thermometer.The test results show that,under the cycle condition,the temperature of the power battery at 1650s has exceeded the optimal working temperature range,and the maximum temperature reached 43℃.(4)The air-cooled wind speeds corresponding to the cooling capacity of the parallel hybrid vehicle engine at three operating speeds were calculated to be 2.7m/s,3.8m/s and 4.2m/s,respectively,and the air-cooled temperature was 291.15K.Using the fluid dynamics simulation software Fluent 19.0 as the simulation platform,the heat dissipation effect of the thermal management system of power battery based on adsorption refrigeration was simulated and analyzed.The results show that under different wind speeds,the battery temperature is always controlled within 40℃,and the maximum temperature difference is within 5℃.The temperature of the battery pack is consistent and good to meet the heat dissipation requirements,which shows that the cooling capacity generated by the waste heat of the engine has a good effect on the heat dissipation of the power battery;The engine exhaust waste heat is used to perform warm-up simulation analysis on the power battery under different low temperature and cold environments.The results show that under different low-temperature environments,preheating the power battery with exhaust heat from the engine exhaust can quickly heat up to the proper operating temperature of the power battery,indicating that in low temperature and cold environments,using the exhaust heat from the engine to preheat the power battery is a feasible preheating scheme.After energy saving calculation and analysis,the energy saving per 100 kilometers can reach 5.31%～6.76%,which shows that the cooling capacity generated by the waste heat of the engine is used for heat dissipation of the power battery is a feasible energy-saving scheme.