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Research Papers

# Effect of Density Ratio on Flat Plate Film Cooling With Shaped Holes Using 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), 041011 (Apr 21, 2011) (11 pages) doi:10.1115/1.4002988 History: Received June 21, 2010; Revised July 13, 2010; Published April 21, 2011; Online April 21, 2011

## Abstract

Detailed film-cooling effectiveness distributions are obtained on a flat plate using the pressure sensitive paint (PSP) technique. The applicability of the PSP technique is expanded to include a coolant-to-mainstream density ratio of 1.4. The effect of density ratio on the film-cooling effectiveness is coupled with varying blowing ratio $(M=0.25–2.0)$, freestream turbulence intensity $(Tu=1–12.5%)$, and film hole geometry. The effectiveness distributions are obtained on three separate flat plates containing either simple angle, cylindrical holes, simple angle, fanshaped holes $(α=10 deg)$, or simple angle, laidback, fanshaped holes ($α=10 deg$ and $γ=10 deg$). In all three cases, the film-cooling holes are angled at $θ=35 deg$ from the mainstream flow. Using the PSP technique, the combined effects of blowing ratio, turbulence intensity, and density ratio are captured for each film-cooling geometry. The detailed film-cooling effectiveness distributions, for cylindrical holes, clearly show that the effectiveness at the lowest blowing ratio is enhanced at the lower density ratio $(DR=1)$. However, as the blowing ratio increases, a transition occurs, leading to increased effectiveness with the elevated density ratio $(DR=1.4)$. In addition, the PSP technique captures an upstream shift of the coolant jet reattachment point as the density ratio increases or the turbulence intensity increases (at moderate blowing ratios for cylindrical holes). With the decreased momentum of the shaped film-cooling holes, the greatest film-cooling effectiveness is obtained at the lower density ratio $(DR=1.0)$ over the entire range of blowing ratios considered. In all cases, as the freestream turbulence intensity increases, the film effectiveness decreases; this effect is reduced as the blowing ratio increases for all three film hole configurations.

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## Figures

Figure 1

Low speed wind tunnel for film-cooling investigations

Figure 2

Details of film hole configurations (units in centimeters)

Figure 3

PSP calibration curve

Figure 6

Film-cooling effectiveness distributions for laidback, fanshaped holes (Tu=6.8%)

Figure 7

Effect of blowing ratio on the centerline film-cooling effectiveness (Tu=6.8%)

Figure 4

Film-cooling effectiveness distributions for cylindrical holes (Tu=6.8%)

Figure 5

Film-cooling effectiveness distributions for fanshaped holes (Tu=6.8%)

Figure 8

Centerline film-cooling effectiveness comparison with previous studies

Figure 9

Effect of blowing ratio on the laterally averaged film-cooling effectiveness (Tu=6.8%)

Figure 10

Effect of density ratio on the centerline film-cooling effectiveness (Tu=6.8%)

Figure 11

Effect of density ratio on the laterally averaged film-cooling effectiveness (Tu=6.8%)

Figure 12

Film-cooling effectiveness distributions for cylindrical holes (DR=1.0)

Figure 13

Film-cooling effectiveness distributions for fanshaped holes (DR=1.0)

Figure 14

Film-cooling effectiveness distributions for laidback, fanshaped holes (DR=1.0)

Figure 15

Effect of freestream turbulence intensity on the centerline film-cooling effectiveness (DR=1.0)

Figure 16

Effect of freestream turbulence intensity on the laterally averaged film-cooling effectiveness (DR=1.0)

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