GLTRS--Glenn
TITLE AND SUBTITLE:
Turbomachine Sealing and Secondary Flows
Part 2-Review of Rotordynamics Issues in Inherently Unsteady Flow Systems With Small Clearances

AUTHOR(S):
R.C. Hendricks, L.T. Tam, and A. Muszynska

REPORT DATE:
July 2004

FUNDING NUMBERS:
Cost Center 2250000013

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-13662-2

SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES):
National Aeronautics and Space Administration
Washington, DC 20546-0001

REPORT TYPE AND DATES COVERED:
Technical Memorandum

SPONSORING/MONITORING AGENCY REPORT NUMBER:
NASA TM-2004-211991-PART2

SUPPLEMENTARY NOTES:
Portions of this material were presented at Second International Symposium on Stability Control of Rotating Machinery sponsored by Bently Pressurized Bearing Company, Gdansk, Poland, August 4-8, 2003. R.C. Hendricks, NASA Glenn Research Center; L.T. Tam, Lockheed Martin Space Systems Company, Sunnyvale, California 94089; and A. Muszynska, A.M. Consulting, Minden, Nevada 89423. Responsible person, R.C. Hendricks, organization code 5000, 216-977-7507.

ABSTRACT:
Today's computational methods enable the determination of forces in complex systems, but without field validation data, or feedback, there is a high risk of failure when the design envelope is challenged. The data of Childs and Bently and field data reported in NASA Conference Proceedings serve as sources of design information for the development of these computational codes. Over time all turbomachines degrade and instabilities often develop, requiring responsible, accurate, turbomachine diagnostics with proper decisions to prevent failures. Tam et al. (numerical) and Bently and Muszynska (analytical) models corroborate and implicate that destabilizing factors are related through increases in the fluid-force average circumferential velocity. The stability threshold can be controlled by external swirl and swirl brakes and increases in radial fluid film stiffness (e.g., hydrostatic and ambient pressures) to enhance rotor stability. Also cited are drum rotor self-excited oscillations, where the classic "fix" is to add a split or severed damper ring or cylindrical damper drum, and the Benkert-Wachter work that engendered swirl brake concepts. For a smooth-operating, reliable, long-lived machine, designers must pay very close attention to sealing dynamics and diagnostic methods. Correcting the seals enabled the space shuttle main engine high-pressure fuel turbopump (SSME HPFTP) to operate successfully.

SUBJECT TERMS:
Turbomachine; Seals; Dynamics; Antiswirl; CFD; Models; Fluid dynamic forces; Rotor and stator clearances

NUMBER OF PAGES:
78

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