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Research Papers

Effects of Regular and Random Roughness on the Heat Transfer and Skin Friction Coefficient on the Suction Side of a Gas Turbine Vane

[+] Author and Article Information
Jason E. Dees, David G. Bogard

 The University of Texas at Austin, Austin, TX 78712

J. Turbomach 130(4), 041012 (Aug 01, 2008) (7 pages) doi:10.1115/1.2812338 History: Received June 07, 2007; Revised August 15, 2007; Published August 01, 2008

Skin friction coefficients and heat transfer coefficients are measured for a range of regular and random roughnesses on the suction side of a simulated gas turbine vane. The skin friction coefficients are calculated using boundary layer data and the momentum integral method. High resolution surface temperature data measured with an IR camera yield local heat transfer values. 80 grit, 50 grit, 36 grit, and 20 grit sandpapers along with a regular array of conical roughness elements are tested. Measured skin friction coefficient data show that the conical roughness array behaves very similar to the 50 grit, 36 grit, and 20 grit sandpapers in terms of the effect of the roughness on the hydrodynamic boundary layer. In terms of heat transfer, the conical roughness array is most similar to the 80 grit sandpaper, which are both lower than the roughest sandpapers tested. These data show that the particular regular array of roughness elements tested has fundamentally different behavior than randomly rough surfaces for this position on the simulated turbine vane. In addition, this difference is in the opposite direction as seen in previous experimental studies. In order to draw a more general conclusion about the nature of random and regular roughness, a parametric study of regular roughness arrays should be performed.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of the simulated turbine vane test section

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Figure 2

Schematic of test vane detail

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Figure 3

Cp distribution for the vane (from Ref. 9)

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Figure 4

Schematic of regular roughness array

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Figure 5

Mean velocity profiles at s∕C=0.37 for varying surface roughnesses

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Figure 6

Mean velocity profiles at s∕C=0.57 for varying surface roughnesses

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Figure 7

Fluctuating velocity profiles, s∕C=0.37

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Figure 8

Fluctuating velocity profiles, s∕C=0.57

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Figure 9

Skin friction coefficient values for various roughness levels

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Figure 10

Skin friction augmentation factors for various surface roughness levels

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Figure 11

Laterally averaged heat transfer coefficient for various surface roughness levels

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Figure 12

Stanton number augmentation for various surface roughness levels

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Figure 13

Combined St∕(Cf∕2) value for various surface roughness levels

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Figure 14

St∕(Cf∕2) versus roughness level

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