Subharmonic and Quasi-Periodic Motions of an Eccentric Squeeze Film Damper-Mounted Rigid Rotor

[+] Author and Article Information
J. Y. Zhao

Department of Mechanical Engineering, Australian Defence Force Academy, Campbell, ACT 2600, Australia

I. W. Linnett

Department of Mechanical Engineering, Australian Defence Force Academy, Campbell, ACT 2601, Australia

L. J. McLean

Machine Design and Development Manager, A.E. Bishop & Associates Pty Ltd, 10 Waterloo Road, North Ryde, NSW 2113, Australia

J. Vib. Acoust 116(3), 357-363 (Jul 01, 1994) (7 pages) doi:10.1115/1.2930436 History: Received July 01, 1992; Revised September 01, 1993; Online June 17, 2008


When a squeeze-film damper is operated eccentrically, the nonlinear damper forces are no longer radially symmetric and subharmonic and quasi-periodic vibrations may be excited by the rotor unbalance. In this study, the unbalance response of a rigid rotor, supported on an eccentric squeeze film damper, is first approximated by a harmonic series whose coefficients are determined by the collocation method, together with a nonlinear least-square regression. The stability of the resulting periodic solution is then examined using the Floquet transition matrix method. For sufficiently large values of the unbalance and the damper static radial misalignment, it is shown that the approximate harmonic motion loses its stability and bifurcates into a stable subharmonic motion and a quasi-periodic motion at speeds above twice the system critical speed. This analytical finding is verified by a numerical integration in forms of the Poincaré map, the rotor trajectory, the bifurcation diagram, and the power spectrum. It is suggested that stability analysis and numerical integration should always be incorporated into an approximate analytical method to achieve an adequate approximation. The results of this study show that the introduction of squeeze-film dampers may give rise to the undesirable nonsynchronous vibrations, which limits the maximum speed at which dampers should be used.

Copyright © 1994 by The American Society of Mechanical Engineers
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