Thermodynamic Analysis And Cooling System Optimization Of Axial Flux Hub Motor

With the issue of environmental degradation and energy shortage put forward,new energy technology has gradually attracted the attention and support of various countries.Compared with traditional vehicles,electric vehicles do not use fossil energy and can achieve zero emissions,which is of great significance for environmental protection.As the power source of electric vehicles,the drive motor needs to meet the power requirements of the vehicle in motion.Compared with the traditional radial flux motor,the axial flux motor has higher power density and the advantage of compact structure,so it is more suitable for new energy vehicles with limited space.The electric drive system of new energy vehicles still adopts centralized drive,and the output torque of the motor is transmitted to the wheels through the drive system.In the process of power transmission,energy loss will be caused,and the drive system also needs a certain cost.Compared with the centralized drive,the distributed hub drive has higher working efficiency without the energy loss of the transmission system.In this paper,the development history of axial flux-hub motors is summarized,the existing problems of axial flux-hub motors are analyzed,and a direct cooling Yokeless and Segmented Armature Axial Flux Machine(YASA)for vehicle hub driving is proposed.Based on the knowledge of heat transfer and computational fluid dynamics(CFD),the heat transfer model and pressure drop model of the cooling system were established,and the number of parallel connections and pipe diameter of the cooling system were optimized according to the numerical analysis method,considering the heat transfer performance and pressure loss of the cooling system.Then,a three-dimensional CFD model of the optimized motor was established,and the stator loss of the motor was analyzed.According to the winding structure of YASA motor,an equivalent model of secondary winding was proposed to calculate the equivalent thermal conductivity of its winding.In addition,the planetary reducer is analyzed,the heat loss generated by the planetary reducer is obtained,the convection boundary condition is solved,and the influence of the friction heat on the motor is analyzed.After that,the external convection boundary conditions of the motor were solved,and the steady-state temperature field of the motor was analyzed by using the Finite Element Method(FEM).In order to verify the reliability of axial flux-hub motor,the influence of braking heat on the hub motor under emergency braking and continuous braking on long slope is analyzed in this paper,and the simulation results are verified through the bench test of the motor,which proves that the motor has high reliability.