Effects of Bulk Flow Pulsations on Film-Cooled Boundary Layer Structure

[+] Author and Article Information
P. M. Ligrani, R. Gong, J. M. Cuthrell

Convective Heat Transfer Laboratory, Department of Mechanical Engineering, University of Utah, Salt Lake City, Utah 84112

J. S. Lee

Turbo and Power Machinery Research Center, Department of Mechanical Engineering, Seoul National University, Seoul 151-742, Republic of Korea

J. Fluids Eng 119(1), 56-66 (Mar 01, 1997) (11 pages) doi:10.1115/1.2819120 History: Received July 10, 1995; Revised June 07, 1996; Online December 04, 2007


Experimental results are presented which describe the effects of bulk flow pulsations on film cooled boundary layer structure. The film is produced by a single row of simple angle film cooling holes and the pulsations are in the form of sinusoidal variations of static pressure and streamwise velocity. Such pulsations are important in turbine studies because: (i) static pressure pulsations result in significant periodic variations of film cooling flow rates, coverage, and trajectories, and (ii) static pressure pulsations occur near blade surfaces in operating engines from passing shock waves and potential flow interactions between moving blade rows. Distributions of ensemble-averaged and time-averaged Reynolds stress tensor components are presented for x/d of 4.5, 9.8, 16.4, and 24.1 along with distributions of streamwise mean velocity and streamwise mean vorticity, where x is streamwise distance from the downstream edge of the holes and d is hole diameter. Important changes from the imposed bulk flow pulsations are evident in all measured quantities, especially just downstream of the holes at x/d = 4.5. Here, Maximum Reynolds shear stresses −2u′v ′ /u∞ 2 are reduced by the pulsations in regions containing the largest film concentrations. This is because the shear layer produced by the injectant oscillates its position as each pulsations is imposed. This causes the shear layer to become more diffused as it is spread over a larger spatial volume.

Copyright © 1997 by The American Society of Mechanical Engineers
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