Vortex Shedding From Struts in an Annular Exhaust Diffuser

[+] Author and Article Information
T. F. Fric, R. Villarreal, R. O. Auer

General Electric Company, Corporate Research & Development, 1 Research Circle, Niskayuna, NY 12309

M. L. James, D. Ozgur, T. K. Staley

General Electric Company, Power Systems, 1 River Road, Schenectady, NY 12345

J. Turbomach 120(1), 186-192 (Jan 01, 1998) (7 pages) doi:10.1115/1.2841380 History: Received February 01, 1996; Online January 29, 2008


Results from scale-model experiments and industrial gas turbine tests show that strut vortex shedding in an annular exhaust diffuser can effectively be modified by adding tapered chord to the struts. The struts are bluff bodies at full-speed, no-load conditions, when inlet swirl is close to 60 deg. Data from wind tunnel tests show that wake Strouhal number is 0.47, larger than that expected for an isolated cylinder wake. This value of Strouhal number agrees with those measured in full-scale exhaust diffusers. Wind tunnel tests showed that a strut with tapered chord most effectively reduced wake amplitudes and shifted shedding frequency. The tapered strut was also effective in reducing shedding amplitude in a scale-model diffuser. Finally, gas turbine tests employing a tapered strut showed significant reductions in unsteady pressure and noise. A major benefit of strut taper is a reduction of noise by uncoupling of vortex shedding from acoustic resonant response.

Copyright © 1998 by The American Society of Mechanical Engineers
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