Study On Modeling And Analysis For Random Vibration Of Centrifugal Compressor Impellers

The impeller is the principal part of a centrifugal compressor for compressing gas and doing work on gas by rotating. The pressure that gas reacted on the impeller is a typical random excitation, so the impeller aerodynamic problem by random loads is typical fluid-structure interaction problems. In many engineering accident, the damage of the impellers is caused by the high cycle fatigue of the material when the random aerodynamic excitation is excited. Therefore, the stress analysis of the impeller has the actual value of preventing fatigue damage and verifying the impeller reliability.In the past, the dynamic stress analysis of the impeller was mainly based on the static load or the 5% static load, and the calculation of the blade was flawed. In order to more accurately calculate the impeller dynamic strength, judge the impeller failure and fatigue failure, this paper carried out the targeted of based on dynamic design of centrifugal impeller random vibration problem research, the specific content as follows:Firstly, obtain unsteady aerodynamic loading impeller flow solid coupling response by weak one-way coupling method, extraction the numerical results with the experimental data were compared to verify the dynamic calculation of the credibility.Secondly, for impeller fluid solid coupling transient solution, weak coupling confluence structure interface data exchange is more complex and the solution of the problem is time-consuming in the time domain, put forward the application of arbitrary geometrical shape leaves the surface load of rapid modeling method, the method based on the engineering fluid meter experience and meet any given mathematics is assumed.Then, the article quotes solving structural dynamic response of stationary random action by the pseudo excitation method, detailing the basic principle of pseudo excitation method, the calculation method of multi dimensional multi point virtual excitation is deduced, and the method and process of realizing multi dimensional multi point virtual excitation in ANSYS is given.Since then, the random problem of semi open impeller based on dynamic design is analyzed by third and four chapters. According to the application method of virtual excitation method of impeller by completely irrelevant excitation in ANSYS, the first step through the blade surface load fast modeling algorithm to generate the impeller surface pressure mean; the second step according to the amplitude frequency curve of dynamic strain test results to determine the frequency components of the design of pneumatic load, the blade surface pressure amplitude load model established quickly any algorithm, generate pressure pulsation by third step impeller surface; improved periodgram method, through MATLAB program of power on the impeller surface pressure pulsation spectrum estimation, power spectrum obtained pressure; the last step using ANSYS harmonic response analysis module analyzes the impeller single sector model, extraction focuses on 200 node displacement dangerous area and the stress power spectrum, the maximum frequency of dynamic response is determined and the corresponding hot.At last, the fatigue damage of the impeller dangerous point is calculated by the fatigue life estimation method based on the fifth chapter, and the fatigue life of the impeller is given.