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Research Papers

Effect of Freestream Turbulence Intensity on Film Cooling Jet Structure and Surface Effectiveness Using PIV and PSP

[+] Author and Article Information
Lesley M. Wright

Department of Mechanical Engineering, Baylor University, Waco, TX 76798-7356lesley_wright@baylor.edu

Stephen T. McClain, Michael D. Clemenson

Department of Mechanical Engineering, Baylor University, Waco, TX 76798-7356

J. Turbomach 133(4), 041023 (Apr 26, 2011) (12 pages) doi:10.1115/1.4003051 History: Received June 23, 2010; Revised July 17, 2010; Published April 26, 2011; Online April 26, 2011

An experimental investigation of film cooling jet structure using two-dimensional particle image velocimetry (PIV) has been completed for cylindrical, simple angle (θ=35deg) film cooling holes. The PIV measurements are coupled with detailed film cooling effectiveness distributions on the flat plate obtained using a steady state, pressure sensitive paint (PSP) technique. Both the flow and surface measurements were performed in a low speed wind tunnel where the freestream turbulence intensity was varied from 1.2% to 12.5%. With this traditional film cooling configuration, the blowing ratio was varied from 0.5 to 1.5 to compare the jet structure of relatively low and high momentum cooling flows. Velocity maps of the coolant flow (in the streamwise direction) are obtained on three planes spanning a single hole: centerline, 0.25D, and 0.5D (outer edge of the film cooling hole). From the seeded jets, time averaged, mean velocity distributions of the film cooling jets are obtained near the cooled surface. In addition, turbulent fluctuations are obtained for each flow condition. Combining the detailed flow field measurements obtained using PIV (both instantaneous and time averaged) with detailed film cooling effectiveness distributions on the surface (PSP) provides a more complete view of the coolant jet-mainstream flow interaction. Near the edge of the film cooling holes, the turbulent mixing increases, and as a result the film cooling effectiveness decreases. Furthermore, the PIV measurements show the increased mixing of the coolant jet with the mainstream at the elevated freestream turbulence level resulting in a reduction in the jet to effectively protect the film cooled surface.

Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 6

Film cooling jet structure with M=1.0, Tu=1.2%

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Figure 7

Film cooling jet structure with M=1.0, Tu=12.5%

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Figure 8

Film cooling jet structure with M=1.5, Tu=1.2%

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Figure 9

Film cooling jet structure with M=1.5, Tu=12.5%

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Figure 10

Streamwise velocity profiles

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Figure 11

Combined PIV and PSP measurements for M=0.5, Tu=1.2%

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Figure 12

Combined PIV and PSP measurements for M=0.5, Tu=12.5%

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Figure 13

Combined PIV and PSP measurements for M=1.0, Tu=1.2%

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Figure 14

Combined PIV and PSP measurements for M=1.0, Tu=12.5%

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Figure 15

Combined PIV and PSP measurements for M=1.5, Tu=1.2%

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Figure 16

Combined PIV and PSP measurements for M=1.5, Tu=12.5%

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Figure 17

Centerline comparison of film cooling effectiveness and turbulent thicknesses

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Figure 5

Film cooling jet structure with M=0.5, Tu=12.5

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Figure 4

Film cooling jet structure with M=0.5, Tu=1.2%

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Figure 3

PIV measurement plane locations

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Figure 2

Details of cylindrical film cooling geometry (units in centimeters)

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Figure 1

Low speed wind tunnel for film cooling investigation

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