Multi-physical Field Analysis And Optimization Of High Speed Oil Immersed Generator

With the development and innovation of global aerospace technology,there are higher demands on the performance of aircraft.High speed oil immersed generators are widely used in aviation starter system,and high speed oil immersed generators are one of the most important parts of aircraft power supply system.The high speed oil immersed generator not only retains the advantages of the high speed permanent magnet synchronous motor,including light weight,high power density and high reliability but also has the cooling structure of direct oil immersed inside the motor,which solves the problem of heat dissipation of the motor under bad aviation conditions.However,the direct oil immersion method will bring about a large rotor friction loss,which needs to be accurately calculated and reduced by design.Aiming at the problems of high speed oil immersed generator,which is applied in high speed and high temperature scene and the rotor friction loss is large,the electromagnetic design,stress check,fluid analysis and thermal field research are carried out in this article.Finally,a high speed oil immersed generator is designed by using the method of multi-field analysis,which is used in aviation generator system.Firstly,the basic principle of the high speed oil-immersed generator is given in this article,and the problems of motor loss,temperature rise,efficiency and power density are considered comprehensively.The structure and material of the fixed rotor are selected reasonably,and the key parameters are preliminarily determined.The preliminary electromagnetic design scheme is formulated,and the simulation results of the no-load and load characteristics of the motor are given.Secondly,this article studies the mechanism of rotor oil frictional loss caused by the immersed structure of the high-speed oil-immersed generator.By simplifying the flow field structure,the rotor oil frictional loss of the high-speed oil-immersed generator is accurately calculated by CFD numerical simulation method,and the exponential relationship between the oil frictional loss and the speed in the analytical method is corrected.The relevant factors affecting rotor oil frictional loss in engineering practice were studied,and the effects of motor operating parameters,structural parameters and technological parameters on rotor oil frictional loss were determined,which provided an important basis for optimizing motor structure and reducing rotor oil frictional loss.Thirdly,this article analyzed the internal heat transfer mechanism of the high-speed oil-immersed generator,established the three-dimensional calculation model of the motor and the internal flow field model with the method of winding equivalent treatment,analyzed and calculated the heat source density of each component,and finally solved the internal flow field distribution of the motor and the temperature distribution of each component of the motor through the heat flow coupling method.The good heat dissipation effect of direct oil cooling is verified.Finally,according to the optimization objectives,this article puts forward the multi-physical field optimization design process of high-speed oil-immersed generator,combines the constraints of multi-physical field,comprehensively considers the effects of various parameters on motor performance,optimizes the preliminary scheme of high-speed oil-immersed generator,and compares the schemes before and after optimization,and gives the final optimization results.To sum up,for the special occasion applied in the harsh environment of aerospace,this article designs a high-speed oil-immersed generator by the method of multi-field analysis.Through the electromagnetic characteristics research,rotor oil frictional loss research,thermal characteristics research and other aspects of the motor design and optimization.