Research On Heating And Cooling Of In-wheel Motor Drive System

Environmental and energy problem have become obstacles to China's sustainable development.With the growing shortage of oil resources and the air pollution caused by automobile exhaust emission becoming serious,the development of new energy vehicles and the transition from traditional vehicle to pure electric vehicle are the effective way to solve the problem of energy shortage and environmental pollution.The structure of electric vehicle(EV)driven by in-wheel motor(IWM)is simplified and the transmission mechanism such as the differential is omitted.The IWM drive EV is the main product in the field of pure electric vehicle because of its obvious technical advantages in vehicle general arrangement structure,chassis active control and operational convenience.The IWM generally has high torque / power density to satisfy the requirements of the multi-mode drive of vehicles,and can withstand the high temperature,vibration and other harsh working conditions.On the other hand,the loss density is increased,resulting in overheating of the motor overheating.At the same time,the heat dissipation is poor because of the narrow-closed installation and the stale air.If the heat of the IWM cannot be dissipated in time,it will not only affects the performance of the insulation and permanent magnet,but also reduces the motor life and threats to the safe operation of the vehicle.Accordingly,it is of great significance for the reduction of temperature and the safe operation of IWM drive vehicles to accurately calculate the motor loss and the motor temperature distribution.The detailed work are as follows:(1)Structure introduction and motor loss analysis of IWM drive system.Firstly,the structure of IWM drive system,the structure parameters and performance parameters are introduced;Secondly,the core loss,winding loss and permanent magnet eddy current loss of the IWM under different working conditions are simulated and analyzed by the Ansoft Maxwell Software.The temperature field characteristics are further analyzed on the premise of calculating the heat generation rate of each component as the heat load.(2)The research of air flow field characteristics of vehicle at different vehicle velocities.An electric vehicle driven by a rear-drive IWM is taken as the research object based on the established vehicle model with the critical components in this paper.The air flow field characteristics around the IWM and the influence of vehicle velocity are obtained by analyzing the flow field characteristics of vehicle at different vehicle velocities.Meanwhile,the convective heat transfer coefficient of each surface of the IWM is calculated at different velocities according to the results of the flow field characteristics analysis to provide accurate boundary conditions for subsequent calculation of temperature field characteristics.(3)Study on thermal characteristics of IWM drive system under different cooling structures.The thermal characteristics of IWM drive system are analyzed by natural cooling,the parallel cooling structure,axial cooling structure and spiral cooling structure based on the determined heat load and convective heat transfer coefficient.The cooling and heat dissipation effects of IWM drive system with various cooling structures are analyzed and compared from two aspects of maximum temperature and temperature difference of each component under the rated and extreme conditions to obtain the appropriate cooling structure for IWM drive system.(4)Optimized design of the cooling structure for IWM drive system.Based on the design experiment,the inlet flow rate,the inlet and outlet diameter,the channel numbers,the channel height and the channel ribs thickness of cooling structure are taken as optimization parameters,and the maximum temperature of insulation and permanent magnet and temperature difference of insulation under rated conditions are taken as optimization objectives to optimize the cooling structure by the method of the multivariate linear regression equation and particle swarm optimization.Finally,the final cooling structure of IWM drive system is determined,and it can also meet the requirements of the IWM drive system under the extreme conditions.