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TECHNICAL PAPERS

# Nonlinear Behavior Analysis of a Rotor Supported on Fluid-Film Bearings

[+] Author and Article Information
Guangyan Shen, Zhonghui Xiao, Wen Zhang

Department of Mechanics and Engineering Science, Fudan University, Shanghai 200433, P. R. China

Tiesheng Zheng1

Department of Mechanics and Engineering Science, Fudan University, Shanghai 200433, P. R. Chinazhengts@fudan.edu.cn

1

Corresponding author.

J. Vib. Acoust 128(1), 35-40 (Jul 14, 2005) (6 pages) doi:10.1115/1.2149394 History: Received November 05, 2003; Revised July 14, 2005

## Abstract

A fast and accurate model to calculate the fluid-film forces of a fluid-film bearing with the Reynolds boundary condition is presented in the paper by using the free boundary theory and the variational method. The model is applied to the nonlinear dynamical behavior analysis of a rigid rotor in the elliptical bearing support. Both balanced and unbalanced rotors are taken into consideration. Numerical simulations show that the balanced rotor undergoes a supercritical Hopf bifurcation as the rotor spin speed increases. The investigation of the unbalanced rotor indicates that the motion can be a synchronous motion, subharmonic motion, quasi-period motion, or chaotic motion at different rotor spin speeds. These nonlinear phenomena are investigated in detail. Poincaré maps, bifurcation diagram and frequency spectra are utilized as diagnostic tools.

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## Figures

Figure 6

Orbit and the projected Poincaré map of synchronous motion and quasi-periodic motion. (Top) Synchronous motion for σ=20; (a) orbit, (b) projected Poincaré map. (Bottom) Quasi-perodic motion for σ=35; (c) orbit, (d) projected Poincaré map

Figure 7

Orbit and mode locking diagram of subharmonic motion. (a) 1∕5 subharmonic motion for σ=45; (b) 1∕2 subharmonic motion for σ=65; (c) 1∕3 subharmonic motion for σ=190

Figure 8

The orbit of journal, projected Poincaré map, and power spectrum of journal displacement in horizontal direction of chaotic motion for σ=100

Figure 1

Model of the rotor supported by two elliptical bearings

Figure 2

Cross section of journal and one pad of bearing in local coordinates

Figure 3

Comparison of the fluid-film force between two methods

Figure 4

Hopf bifurcation and limit circle of balanced rotor, (a) Hopf bifurcation; (b) limit circle for ω=5000

Figure 5

Bifurcation diagram

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