Experimental Force Coefficients for a Two-Bladed Labyrinth Seal and a Four-Pocket Damper Seal

[+] Author and Article Information
David Ransom

Rocketdyne Division, Boeing, Canoga Park, CA 91309

Jiming Li

Elliot Company, Jeannette, PA 15644

Luis San Andrés, John Vance

Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843-3123

J. Tribol 121(2), 370-376 (Apr 01, 1999) (7 pages) doi:10.1115/1.2833949 History: Received January 15, 1998; Revised June 18, 1998; Online January 24, 2008


Experiments are presented to identify the stiffness and damping force coefficients of a two-blade, teeth on stator labyrinth seal with diverging clearance and its modified version as a four-pocket gas damper seal. The seals were tested without journal rotation and at rotor speeds of 1500 rpm and 3000 rpm for seal supply to ambient pressure ratios ranging from 1 to 3. Calibrated impact loads excite a flexibly supported housing holding rigidly the test seal. The impact loads and seal displacement and acceleration time responses are measured and recorded as frequency spectra. The instrumental variable filter method is used to identify the seal dynamic force coefficients from the measured transfer functions over a frequency range. The experiments demonstrate the four pocket gas damper seal has large (positive) direct damping coefficients and relatively small (negative) direct stiffness coefficients. The two bladed labyrinth seal exhibits positive direct stiffness and negative damping force coefficients. The leakage performance of both seals is nearly identical. The four pocket damper seal clearly outperforms the labyrinth seal in terms of rotordynamic forces. Both seals show a minimal amount of cross-coupling force effects, well within the experimental uncertainty.

Copyright © 1999 by The American Society of Mechanical Engineers
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