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Research Papers

Influence of Coolant Density on Turbine Blade Film-Cooling Using Pressure Sensitive Paint Technique

[+] Author and Article Information
Diganta P. Narzary, Kuo-Chun Liu, Akhilesh P. Rallabandi

Department of Mechanical Engineering, Turbine Heat Transfer Laboratory, Texas A&M University, College Station, TX 77843-3123

Je-Chin Han

Department of Mechanical Engineering, Turbine Heat Transfer Laboratory, Texas A&M University, College Station, TX 77843-3123jc-han@tamu.edu

J. Turbomach 134(3), 031006 (Jul 14, 2011) (10 pages) doi:10.1115/1.4003025 History: Received July 03, 2010; Revised July 07, 2010; Published July 14, 2011; Online July 14, 2011

Adiabatic film-cooling effectiveness is examined on a high-pressure turbine blade by varying three critical engine parameters, viz., coolant blowing ratio, coolant-to-mainstream density ratio, and freestream turbulence intensity. Three average coolant blowing ratios (BR=1.2, 1.7, and 2.2 on the pressure side and BR=1.1, 1.4, and 1.8 on the suction side), three average coolant density ratios (DR=1.0, 1.5, and 2.5), and two average freestream turbulence intensities (Tu=4.2% and 10.5%) are considered. Conduction-free pressure sensitive paint (PSP) technique is adopted to measure film-cooling effectiveness. Three foreign gases—N2 for low density, CO2 for medium density, and a mixture of SF6 and argon for high density are selected to study the effect of coolant density. The test blade features two rows of cylindrical film-cooling holes on the suction side (45 deg compound), 4 rows on the pressure side (45 deg compound) and 3 around the leading edge (30 deg radial). The inlet and the exit Mach numbers are 0.24 and 0.44, respectively. The Reynolds number of the mainstream flow is 7.5×105 based on the exit velocity and blade chord length. Results suggest that the PSP is a powerful technique capable of producing clear and detailed film-effectiveness contours with diverse foreign gases. Large improvement on the pressure side and moderate improvement on the suction side effectiveness is witnessed when blowing ratio is raised from 1.2 to 1.7 and 1.1 to 1.4, respectively. No major improvement is seen thereafter with the downstream half of the suction side showing drop in effectiveness. The effect of increasing coolant density is to increase effectiveness everywhere on the pressure surface and suction surface except for the small region on the suction side, xss/Cx<0.2. Higher freestream turbulence causes effectiveness to drop everywhere except in the region downstream of the suction side where significant improvement in effectiveness is seen.

Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of (a) experimental facility and (b) Linear cascade

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Figure 2

Blade coolant passages and hole locations

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Figure 3

Surface Mach number distribution and coolant hole locations

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Figure 4

Velocity profile and freestream turbulence intensity measured at the cascade inlet

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Figure 5

A basic PSP setup

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Figure 6

Calibration of PSP

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Figure 7

Coolant-to-mainstream pressure ratio

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Figure 8

Adiabatic effectiveness distribution at three different blowing ratios (DR=2.5, Tu=10.5%)

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Figure 9

Magnified view of coolant rows PS1 and SS1around the midspan; BRPS=1.7, BRSS=1.8 (DR=2.5, Tu=10.5%)

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Figure 10

Spanwise-averaged effectiveness as a function of blowing ratio (Tu=10.5%)

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Figure 11

Adiabatic effectiveness distribution at three different density ratios (Tu=10.5%)

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Figure 12

Spanwise-averaged effectiveness as a function of density ratio (Tu=10.5%)

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Figure 13

Adiabatic film-cooling effectiveness distribution at low freestream turbulence intensity of 4.2% (BRPS=1.7, BRSS=1.4, and DR=2.5)

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Figure 14

Spanwise-averaged adiabatic effectiveness as a function of freestream turbulence intensity

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Figure 15

Spanwise-averaged effectiveness as a function of momentum flux ratio, DR=2.5, Tu=10.5%

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Figure 16

Comparison of laterally averaged effectiveness with previous study

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