Rotordynamic Evaluation of a Near-Tangential-lnjection Hybrid Bearing

[+] Author and Article Information
Franck Laurant

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

Dara W. Childs

Texas A&M University, Jordan Professor of Mechanical Engineering, Turbomachinery Laboratory, College Station, TX 77840-3254

J. Tribol 121(4), 886-891 (Oct 01, 1999) (6 pages) doi:10.1115/1.2834151 History: Received December 21, 1998; Revised April 16, 1999; Online January 24, 2008


Given the inherent DN and assembly limitations of rolling-element bearings, research is underway to develop hybrid bearings (combining hydrostatic and hydrodynamic effects) for their replacement. Hybrid bearings develop cross-coupled stiffness coefficients due to fluid rotation, leading to predictions of onset speeds of instability and potential limitations in their range of application. Injecting fluid into a bearing recess against rotation, versus the customary radial injection, can reduce the circumferential flow and the cross-coupled-stiffness coefficients, and increase the margin of stability. Test results are presented here for a hybrid bearing with against-rotation injection. The bearing has a 76.4 mm diameter with LID = 1, and Cr IR = 0.001. Data are presented for 55°C water at three speeds out to 25000 rpm and three pressures out to 7.0 MPa. Compared to a radial-injection hybrid bearing, experiments show injection against rotation enhances stability, yielding reductions of cross-coupled stiffness coefficients and whirl frequency ratios. However, increased flow rate and a drop of effective stiffness with increasing speed adversely affect the bearing performance. The prediction code developed by San Andres (1995) includes angled-orifice injection. The code correctly predicts trends, but at low speed, measured cross-coupled stiffness coefficients are positive, versus a prediction of larger negative values.

Copyright © 1999 by The American Society of Mechanical Engineers
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