The nonlinear dynamic behavior of elliptic bearing-rotor system was investigated by working on 200 MWsteam turbine as an example.The finite element method was employed to establish a dynamical model of the system and a nonlinear model derived from the variational principle was adopted to describe the oil force of elliptic bearings.Then

the nonlinear dynamic system with 608-degree-of-freedom was reduced to a 30-degree-of-freeodm model in terms of the fixed interface mode synthesis method.The Rouge-Kutta method was employed to solve the reduced model numerically

and the frequency-response curve

the bifurcation diagram

and the three dimensional spectral plot obtained were used to analyze the stability of the rotor-bearing system.The effects

on the dynamic behavior of the system

of the eccentricity

the oil viscosity and the length-to-diameter ratio of bearing were discussed in terms of the frequency-response curve.The numerical results show that the stability range of the elliptic bearing-rotor model is larger than that of the circular bearing-rotor system.