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Research Papers

Heat Transfer Augmentation Downstream of Rows of Various Dimple Geometries on the Suction Side of a Gas Turbine Airfoil

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

 University of Texas, 1 University Station C 2200, Austin, TX 78712

Ronald S. Bunker

 GE Global Research, One Research Circle, Niskayuna, NY 12309

J. Turbomach 132(3), 031010 (Mar 25, 2010) (7 pages) doi:10.1115/1.3149284 History: Received October 08, 2008; Revised November 18, 2008; Published March 25, 2010; Online March 25, 2010

Heat transfer coefficients were measured downstream of a row of shaped film cooling holes, as well as elliptical, diffuser, and teardrop shaped dimples, simulating depressions due to film coolant holes of different shapes. These features were placed on the suction side of a simulated gas turbine vane. The dimples were used as approximations to film cooling holes after the heat transfer levels downstream of active fan shaped film cooling holes was found to be independent of film cooling. The effects of the dimples were tested with varying approach boundary layers, freestream turbulence intensity, and Reynolds numbers. For the case of an untripped (transitional) approach boundary layer, all dimple shapes caused approximately a factor of 2 increase in heat transfer coefficient relative to the smooth baseline condition due to the dimples effectively causing boundary layer transition downstream. The exact augmentation varied depending on the dimple geometry: diffuser shapes causing the largest augmentation and teardrop shapes causing the lowest augmentation. For tripped (turbulent boundary layer) approach conditions, the dimple shapes all caused the same 20% augmentation relative to the smooth tripped baseline. The already turbulent nature of the tripped approach flow reduces the effect that the dimples have on the downstream heat transfer coefficient.

Copyright © 2010 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 area of interest

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Figure 3

Cp distribution for the vane

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Figure 4

Schematic of (a) elliptical dimple, (b) teardrop dimple, (c) diffuser dimple, and (d) shaped film cooling hole

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Figure 5

Boundary layer profiles at s/C=0.35 for tripped and untripped approach conditions

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Figure 6

h/h0 due to shaped hole film cooling: Re=1.06×106, high Tu, untripped approach flow, HSL, untripped reference condition

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Figure 7

h/h0 due to shaped hole film cooling: Re=1.06×106, high Tu, untripped approach flow, HSL, tripped reference condition

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Figure 8

h/h0 due to shaped hole film cooling: Re=1.06×106, high Tu, tripped approach flow, HSL, tripped reference condition

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Figure 9

h/h0 due to shaped hole film cooling: Re=1.06×106, high Tu, untripped approach flow, UHSL, tripped reference condition

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Figure 10

h/h0 due to shaped hole film cooling: Re=1.06×106, high Tu, tripped approach flow, UHSL, tripped reference condition

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Figure 11

Effect of HSL and UHSL on h/h0: Re=1.06×106, high Tu, untripped approach flow, tripped reference condition

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Figure 12

h0 values for heated and unheated starting length, tripped approach condition

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Figure 13

Laterally averaged h values at s/C=0.41, all configurations

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Figure 14

Effect of dimple shape on h/h0; untripped approach condition, low Tu, Re=1.06×106, HSL tripped, high Tu, low Re reference

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Figure 15

Effect of dimple shape h/h0; tripped and untripped approach conditions, low Tu, Re=1.06×106, HSL tripped, high Tu, low Re reference

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Figure 16

Effect of dimple shape on h/h0; tripped and untripped approach conditions, low Tu, Re=1.88×106, HSL tripped, high Tu, high Re reference

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Figure 17

Effect of varying freestream turbulence intensity on h/h0, no trip, Re=1.06×106, HSL

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