GLTRS--Glenn
TITLE AND SUBTITLE:
The Role of Radial Clearance on the Performance of Foil Air Bearings

AUTHOR(S):
Kevin Radil, Samuel Howard, and Brian Dykas

REPORT DATE:
July 2002

FUNDING NUMBERS:
WU-708-18-13-00
1L161102AH45

PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES):
National Aeronautics and Space Administration
John H. Glenn Research Center at Lewis Field
Cleveland, Ohio 44135-3191

PERFORMING ORGANIZATION REPORT NUMBER:
E-13450

SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES):
National Aeronautics and Space Administration
Washington, DC 20546-0001
and
U.S. Army Research Laboratory
Adelphi, Maryland 20783-1145

REPORT TYPE AND DATES COVERED:
Technical Memorandum

SPONSORING/MONITORING AGENCY REPORT NUMBER:
NASA TM-2002-211705
ARL-TR-2769

SUPPLEMENTARY NOTES:
Prepared for the International Joint Tribology Conference cosponsored by the American Society of Mechanical Engineers and the Society of Tribologists and Lubrication Engineers, Cancun, Mexico, October 27-30, 2002. Kevin Radil, U.S. Army Research Laboratory, NASA Glenn Research Center; Samuel Howard, NASA Glenn Research Center; and Brian Dykas, Ohio Aerospace Institute, Brook Park, Ohio 44142. Responsible person, Kevin Radil, organization code 5960, 216-433-5047.

ABSTRACT:
Load capacity tests were conducted to determine how radial clearance variations affect the load capacity coefficient of foil air bearings. Two Generation III foil air bearings with the same design but possessing different initial radial clearances were tested at room temperature against an as-ground PS304 coated journal operating at 30 000 rpm. Increases in radial clearance were accomplished by reducing the journal's outside diameter via an in-place grinding system. From each load capacity test the bearing load capacity coefficient was calculated from the rule-of-thumb (ROT) model developed for foil air bearings. The test results indicate that, in terms of the load capacity coefficient, radial clearance has a direct impact on the performance of the foil air bearing. Each test bearing exhibited an optimum radial clearance that resulted in a maximum load capacity coefficient. Relative to this optimum value are two separate operating regimes that are governed by different modes of failure. Bearings operating with radial clearances less than the optimum exhibit load capacity coefficients that are a strong function of radial clearance and are prone to a thermal runaway failure mechanism and bearing seizure. Conversely, a bearing operating with a radial clearance twice the optimum suffered only a 20 percent decline in its maximum load capacity coefficient and did not experience any thermal management problems. However, it is unknown to what degree these changes in radial clearance had on other performance parameters, such as the stiffness and damping properties of the bearings.

SUBJECT TERMS:
Foil air bearing; Gas bearing; Turbomachinery

NUMBER OF PAGES:
20

PDF AVAILABLE FROM URL:
2002/TM-2002-211705.pdf
( 669 KB )
This page contains an Adobe® Acrobat® Reader PDF file. The PDF documents have been created to show thumbnails of each page. If the thumbnails do not display properly, download the file to the hard drive and view through Acrobat® Reader. You can download Acrobat® Reader for free.

NASA NASA GLTRS--Glenn

A service of the NASA Glenn Research Center Logistics and Technical Information Division

Suggestions or questions about this site can be directed to:

NASA official: Technical Publications Manager, Sue.E.Butts@nasa.gov

Web curator: Caroline.A.Rist@grc.nasa.gov

Privacy Policy and Important Notices