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Forced Convection

Unsteady Wake and Coolant Density Effects on Turbine Blade Film Cooling Using Pressure Sensitive Paint Technique

[+] Author and Article Information
Akhilesh P. Rallabandi, Shiou-Jiuan Li

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

Je-Chin Han

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

J. Heat Transfer 134(8), 081701 (Jun 05, 2012) (10 pages) doi:10.1115/1.4006748 History: Received April 10, 2011; Revised March 30, 2012; Published June 05, 2012; Online June 05, 2012

The effect of an unsteady stator wake (simulated by wake rods mounted on a spoke-wheel wake generator) on the modeled rotor blade is studied using the pressure sensitive paint (PSP) mass-transfer analogy method. Emphasis of the current study is on the midspan region of the blade. The flow is in the low Mach number (incompressible) regime. The suction (convex) side has simple angled cylindrical film-cooling holes; the pressure (concave) side has compound angled cylindrical film-cooling holes. The blade also has radial shower-head leading edge film-cooling holes. Strouhal numbers studied range from 0 to 0.36; the exit Reynolds number based on the axial chord is 530,000. Blowing ratios range from 0.5 to 2.0 on the suction side and 0.5 to 4.0 on the pressure side. Density ratios studied range from 1.0 to 2.5, to simulate actual engine conditions. The convex suction surface experiences film-cooling jet lift-off at higher blowing ratios, resulting in low effectiveness values. The film coolant is found to reattach downstream on the concave pressure surface, increasing effectiveness at higher blowing ratios. Results show deterioration in film-cooling effectiveness due to increased local turbulence caused by the unsteady wake, especially on the suction side. Results also show a monotonic increase in film-cooling effectiveness on increasing the coolant to mainstream density ratio.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

3D view of suction type wind tunnel with spoke-wheel wake generator

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Figure 2

View of blade showing arrangement of cooling holes, coolant supply channels, and area painted with PSP

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Figure 3

(a) Principle of measurement using PSP; (b) calibration curve for PSP at three different temperatures

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Figure 4

(a) Measured pressure distribution around model blade; (b) instantaneous hot-wire velocity signal from Ref. [20]; (c) ensemble averaged velocity [20]; (d) ensemble averaged turbulence intensity [20]

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Figure 5

Effect of coolant blowing ratio on film-cooling effectiveness: contour plots. Note that blowing ratios are different on pressure side and suction side. Data acquired at constant DR (1.5) and constant Strouhal number (0.18).

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Figure 6

Effect of blowing ratio on film-cooling effectiveness for three different density ratios. All data are acquired at S = 0.18.

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Figure 7

Effect of Strouhal number on film-cooling effectiveness. For all cases, M = 0.5 on both suction side and pressure side.

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Figure 8

Effect of Strouhal number on film-cooling effectiveness. For all cases, M = 0.75 on suction side and M = 2.0 on pressure side.

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Figure 9

Effect of Strouhal number on film-cooling effectiveness for three separate blowing ratios at DR = 1.0

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Figure 10

Effect of Strouhal number on film-cooling effectiveness for three separate blowing ratios at DR = 1.5

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Figure 11

Effect of density ratio on film-cooling effectiveness. For all cases, M = 0.5 on both sides and S = 0.18.

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Figure 12

Effect of density ratio on film-cooling effectiveness. For all cases, M = 0.75 on suction side, M = 2.0 on pressure side, and S = 0.18.

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Figure 13

Effect of density ratio on film-cooling effectiveness for three different blowing ratios at S = 0.18

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Figure 14

Effect of momentum flux ratio and density ratio on film-cooling effectiveness at four selected locations. (a, b) Pressure side; (c, d) suction side. Locations detailed in Fig. 1.

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Figure 15

Comparison of current PSP data with prior effectiveness data using thermochromic liquid crystals

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