Characterization and Laboratory Simulation of Turbine Airfoil Surface Roughness and Associated Heat Transfer

[+] Author and Article Information
D. G. Bogard, D. L. Schmidt

The University of Texas at Austin, Austin, TX 78712

M. Tabbita

Pratt & Whitney, West Palm Beach, FL 33410

J. Turbomach 120(2), 337-342 (Apr 01, 1998) (6 pages) doi:10.1115/1.2841411 History: Received February 01, 1996; Online January 29, 2008


The physical characteristics of surface roughness observed on first-stage high-pressure turbine vanes that had been in service for a long period were investigated in this study. Profilometry measurements were utilized to provide details of the surface roughness formed by deposits of foreign materials on different parts of the turbine vane. Typical measures of surface roughness such as centerline average roughness values were shown to be inadequate for characterizing roughness effects. Using a roughness shape parameter originally derived from regular roughness arrays, the turbine airfoil roughness was characterized in terms of equivalent sand-grain roughness in order to develop an appropriate simulation of the surface for laboratory experiments. Two rough surface test plates were designed and fabricated. These test plates were evaluated experimentally to quantify the heat transfer rate for flow conditions similar to that which occurs on the turbine airfoil. Although the roughness levels on the two test plates were different by a factor of two, both surfaces caused similar 50 percent increases in heat transfer rates relative to a smooth surface. The effects of high free-stream turbulence, with turbulence levels from 10 to 17 percent, were also investigated. Combined free-stream turbulence and surface roughness effects were found to be additive, resulting in as much as a 100 percent increase in heat transfer rate.

Copyright © 1998 by The American Society of Mechanical Engineers
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