A Simple Stability Analysis for Flexible Rotors in Tilting Pad Bearings

[+] Author and Article Information
E. A. Bulanowski

Solid Mechanics Research & Advanced Product Development, De Laval Turbine, Inc., Trenton, N. J.

J. Mech. Des 100(1), 165-172 (Jan 01, 1978) (8 pages) doi:10.1115/1.3453881 History: Received June 01, 1977; Online October 21, 2010


A simplified stability analysis for flexible rotors in tilting pad bearings is developed which provides a convenient and practical approach for the consideration of nonsynchronous vibrations during the design phase of rotor bearing systems. It is known that the synchronous unbalance response of a single mass Jeffcott rotor in linear isotropic bearings is identical in form to the response of a simple spring-mass-damper system excited by a rotating unbalance. This paper demonstrates that the free vibrations, and hence the system damping factor, of a distributed mass flexible rotor in tilting pad bearings may be analyzed using a single mass, two tier spring-damper model. The relationship between the system damping factor and rotor stability is discussed. Non-synchronous tilting pad bearing characteristics are incorporated into the expression for the damping factor, and nondimensional curves are presented which establish values of the damping factor as a function of operating speed, critical speed, bearing clearance and Sommerfeld number. The subject curves provide a quick method for establishing stability guidelines during rotor design and for comparing existing rotor bearing systems.

Copyright © 1978 by ASME
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