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RESEARCH PAPERS

Rotordynamic Evaluation of a Roughened-Land Hybrid Bearing

[+] Author and Article Information
Patrice Fayolle

SEP, Division of SNECMA, Direction Grosse Propulsion Liquide-BP 802, 27208 Vernon Cedex, France

Dara W. Childs

Texas A&M University,Turbo Machinery Laboratory, College-Statio, TX 77840-3254

J. Tribol 121(1), 133-138 (Jan 01, 1999) (6 pages) doi:10.1115/1.2833794 History: Received January 28, 1998; Revised May 26, 1998; Online January 24, 2008

Abstract

Hybrid bearings represent an attractive alternative to ball bearings for use in highspeed cryogenic turbopumps. However, the internally-developed cross-coupled forces can generate instabilities responsible for a speed limitation of the machine. To reduce these forces and raise the onset speed of instability, the use of deliberately-roughened stators, already successfully tested for liquid “damper” seals, is investigated. Rotor-dynamic results are presented for a five-pocket orifice-compensated hole-pattern-land hybrid bearing tested with water at high speed and high pressure. Experimental data show a good prediction of leakage flow rate and direct damping but a significant improvement in stability compared to a conventional smooth-land hybrid bearing, resulting in an elevation of the onset speed of instability. Comparisons between measurements and predictions from a code developed by San Andres (1994) shows good predictions for flowrate and direct damping but an over prediction for the direct and cross-coupled stiffness coefficients by about 30 and 50 percent, respectively. The use of the Moody friction-factor model is thought to be mainly responsible for the poorer predictions of stiffness coefficients.

Copyright © 1999 by The American Society of Mechanical Engineers
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