Numerical Study On Nonlinear Aerodynamic Excitation Of Rotor-Bearing-Sealing Systems

Muszynska sealing force model is widely used. Otherwise, some sealing force parameters of the model are usually obtained by experience. In addition, the studies are always developed under a certain group of parameters. The sealing parameters can't be decided on concrete sealing structure. Rotor-bearing-sealing system is a typically nonlinear system. At present, the established calculation model hasn't completely seize the multi-tooth, unsteady characters of labyrinth seal under multi-condition. The established model is mainly for single tooth cavity and hasn't considered the effect of unsteady factor in calculation.This paper studies rotor-bearing-sealing system of the large Rotor Vibration Test Desk, which aims to research the variation of internal flow field in 3D comb labyrinth seal of balance disc and nonlinear dynamic characteristics of rotor-bearing-sealing system with multi-tooth sealing force and oil-film force.The specific summaries are as follows:(1) Computational fluid dynamics (CFD) analysis of the balance disc sealing for Rotor Vibration Test Desk, the variation of internal flow field in 3D comb labyrinth seal under twenty working conditions is summarized.(2) According to the CFD results, the sealing forces of rotating shaft wall on sealing teeth are calculated. And the increasing rate of sealing force will be sustained growth with rotating speed and be decreased with pressure difference.(3) According to the CFD results, Muszynska sealing parameters of sealing teeth are determined. Circumferentially-averaged velocity ratio of flow will be slow increase with rotating speed and be increased first and then decreased with pressure difference. Meanwhile Muszynska sealing force model doesn't satisfy the sealing force calculation of large eccentricity.(4) Time histories, orbits of the rotor center, Poincare maps and bifurcation diagrams at the rotor and bearing are used to demonstrate the dynamic features, under the dynamic model of rotor-bearing-sealing system with the combined multi-tooth sealing forces and oil-film forces. The multiple of double period motion under certain rotating speed will be changed with the eccentricity and pressure difference.