| The automotive electric wheel technology greatly simplified the mechanical transmission part of EV,which had the advantages of short drive transmission chain,high transmission efficiency,compact structure,etc.At the same time,the poor heat transfer environment of electric wheel made its heat emission difficult.This paper took the electric wheel with multi PMSMs in parallel working model as research object,and aimed to develop a distributed electric wheel driving system with a completely independent cooling system.In this paper,a detailed study and analysis were carried out on the problems of heat generation,cooling system design and selection,temperature distribution,internal and external flow fields simulation,and cooling structure optimization for electric wheel.The main research contents were as follows:(1)The cause and distribution of each part’s power loss for sub-motor of electric wheel were analyzed,and heat emission requirement of the electric wheel with a completely independent cooling system were clarified.The above studies provided the basis for subsequent temperature field analysis and cooling structure design.(2)On the basis of summarizing the motor’s currently main cooling technologies,combined with the working environment and characteristics of the electric wheel,an electric wheel heat exchange system which was similar to the refrigeration cycle was proposed and its feasibility was discussed.After comparative analysis with current technical conditions,the independent air cooling method was finally selected.(3)For the dual-stator motor model of independent air cooling electric wheel,Fluent was used as the simulation method to establish a simulation model of temperature field and flow field.The temperature distribution and internal flow field characteristics of the in-wheel motor were calculated,and further ways to improve the cooling effect of the motor were proposed.(4)The external flow field of the electric wheel was calculated under the working environment of the vehicle,the features of the external flow field of the electric wheel were analyzed,and the influence of the external flow field distribution on the cooling effect of the electric wheel was studied,which provide directions for optimizing the cooling performance of the electric wheel.(5)Further study had been made on the influences of electric wheel’s cooling performance,including environment temperature,wind speed,and the shape,density,arrangement angle of the motor housing’s fins.Through comparative analysis and optimization,a fin design scheme was proposed to increase the convection heat transfer coefficient of the motor housing and improve the cooling performance of the electric wheel.This paper had studied the independent thermal design for automotive electric wheel and calculation and analysis methods for flow field,which proposed a approach for simplifying the structures of electric wheel system.At the same time,it also had reference value for the design of electric wheel that used non-independent cooling systems. |
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