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TECHNICAL PAPERS

# Linear Stability Analysis of a Tilting-Pad Journal Bearing System

[+] Author and Article Information
Guang Qiao, Liping Wang

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

Tiesheng Zheng

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

J. Tribol 129(2), 348-353 (Dec 05, 2006) (6 pages) doi:10.1115/1.2464136 History: Received March 19, 2006; Revised December 05, 2006

## Abstract

This paper describes a mathematical model to study the linear stability of a tilting-pad journal bearing system. By employing the Newton-Raphson method and the pad assembly technique, the full dynamic coefficients involving the shaft degrees of freedom as well as the pad degrees of freedom are determined. Based on these dynamic coefficients, the perturbation equations including self-excited motion of the rotor and rotational motion of the pads are derived. The complex eigenvalues of the equations are computed and the pad critical mass identified by eigenvalues can be used to determine the stability zone of the system. The results show that some factors, such as the preload coefficient, the pivot position, and the rotor speed, significantly affect the stability of tilting-pad journal bearing system. Correctly adjusting those parameter values can enhance the stability of the system. Furthermore, various stability charts for the system can be plotted.

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## Figures

Figure 1

Figure 9

Modal damping ratios versus δ(Ω=10,000rpm)

Figure 13

Coordinates of a pad and journal in a tilting-pad journal bearing system

Figure 2

Schematic of a three-pad journal bearing system

Figure 3

Nondimensional pad critical mass m¯c versus Ω(Ψ=0.5)

Figure 4

Nondimensional pad critical mass m¯c versus Ψ (a) (Ω=15,000rpm)

Figure 5

Nondimensional pad critical mass m¯c versus Ψ (b) (δ=0.3)

Figure 6

The associated amplitude ratio of complex modes (δ=0.2, Ω=10,000rpm)

Figure 7

The real portion of complex mode shapes (δ=0.2, Ω=10,000rpm)

Figure 8

The imaginary portion of complex mode shapes (δ=0.2, Ω=10,000rpm)

Figure 10

Natural frequencies versus δ(Ω=10,000rpm)

Figure 11

Damping ratios versus Ω(δ=0.2)

Figure 12

Natural frequencies versus Ω(δ=0.2)

## Errata

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