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RESEARCH PAPERS: Gas Turbines: Structures and Dynamics

Experimental Leakage and Rotordynamic Results for Helically Grooved Annular Gas Seals

[+] Author and Article Information
D. W. Childs

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

A. J. Gansle

Sanden International (U.S.A.), Inc., Wylie, TX 75098

J. Eng. Gas Turbines Power 118(2), 389-393 (Apr 01, 1996) (5 pages) doi:10.1115/1.2816601 History: Received February 13, 1995; Online November 19, 2007

Abstract

Rotordynamic-coefficient and leakage test results are presented for three grooved seals with helix angles of 0, 15, and 30 deg against rotation. The seals are 50.8 mm long and 152.4 mm in diameter. Tests were done for two supply pressures (up to 17 bars), three speeds (5000, 12,000, and 16,000 rpm), four pressure ratios, and three inlet fluid prerotation conditions. The results showed that increasing the helix angle yields a progressive reduction in the cross-coupled stiffness coefficient k and a progressive increase in leakage. The helically grooved seals consistently yield negative cross-coupled stiffness coefficients for nonprerotated inlet flow; hence, k in these seals would oppose forward whirl of a rotor. Helically grooved seals become less effective at reducing k with increasing preswirl; hence, for optimum effectiveness they should be used with a swirl brake. Comparison between helically grooved and honeycomb-stator seals showed that helically grooved stators had reduced (negative) whirl-frequency ratios for nonprerotated flows but were no better than honeycomb-stator seals for elevated fluid prerotation. The 15 and 30 deg helix grooves leaked about 1.6 and 2.2 times, respectively, as much as the honeycomb-stator seals.

Copyright © 1996 by The American Society of Mechanical Engineers
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