Study Of Finite Element Method For Rotor-casing System Vibration Charateristic Analysis

Rotor and stator system are the important components of aeroengines. Because vibration coupling effects exist between them cannot be ignored, to calculate the whole model vibration characteristics is of great significance. In this paper, several kinds of finite element analysis method of vibration characteristics of rotor-casing system are compared and their results are analyzed and compared.According to the basic structure of the turbine engine a finite element model of simple rotor-casing system is established. Vibration characteristics of the system are calculated and analyzed using the integral model, separate model, and dimension reduction model respectively. The error was analyzed. With the decrease of casing stiffness, the coupling influence between the rotor system and the casing is increasing. Compared with integral method, the relative error of the whole model calculation result obtained using the separation calculation method is not obvious. With the decrease of casing stiffness, the relative error increases gradually. The analysis method of dimension reduction is adopted to establish the finite element model of the three dimensional casing and one dimensional rotor system, this model can both improve the computation efficiency and reflect the coupling between the rotor system and casing, but in the process of simplification of 3 dimensional model of the rotor system to one dimensional model will introduce other errors.Finally, according to the analysis method of rotor unbalance response excited by one disc and more discs, displacement excitation method of analyzing disc unbalance by restricting disc response displacement is proposed. The response displacements of the discs caused by unbalance excitation and displacements excitation is analyzed and compared respectively. And the result shows that the response displacement of each disc is identical for the two types of excitation at the same rotating speed. In order to prevent the rubbing, according to the relationship between responses and unbalance distribution, the maximum allowable unbalance is obtained with the displacement restriction method.