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Research Papers

Effect of Trench Width and Depth on Film Cooling From Cylindrical Holes Embedded in Trenches

[+] Author and Article Information
Yiping Lu, Alok Dhungel

Mechanical Engineering Department, Virginia Tech, Blacksburg, VA 24061

Srinath V. Ekkad

Mechanical Engineering Department, Virginia Tech, Blacksburg, VA 24061ekkad@vt.edu

Ronald S. Bunker

 GE Global Research Center, Niskayuna, NY 12301

J. Turbomach 131(1), 011003 (Sep 25, 2008) (13 pages) doi:10.1115/1.2950057 History: Received June 11, 2007; Revised July 13, 2007; Published September 25, 2008

The present study is an experimental investigation of film cooling from cylindrical holes embedded in transverse trenches. Different trench depths are considered with two trench widths. Trench holes can occur when blades are coated with thermal barrier coating (TBC) layers. The film-hole performance and behavior will be different for the trench holes compared to standard cylindrical holes that are flush with the surface. The trench width and depth depend on the mask region and the thickness of the TBC layer. Detailed heat transfer coefficient and film effectiveness measurements are obtained simultaneously using a single test transient IR thermography technique. The study is performed at a single mainstream Reynolds number based on freestream velocity and film-hole diameter of 11,000 at four different coolant-to-mainstream blowing ratios of 0.5, 1.0, 1.5, and 2.0. The results show that film effectiveness is greatly enhanced by the trenching due to the improved two-dimensional nature of the film and lateral spreading. The detailed heat transfer coefficient and film effectiveness contours provide a clear understanding of the jet-mainstream interactions for different hole orientations. Computational fluid dynamics simulation using FLUENT was also performed to determine the jet-mainstream interactions to better understand the surface heat transfer coefficient and film effectiveness distributions.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 3

Test plate geometry without trench

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Figure 4

Eight cases with different hole configurations studied

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Figure 5

Computational grid details

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Figure 6

Detailed film effectiveness distributions for all cases at different blowing ratios

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Figure 7

Computed centerline nondimensional temperature contours demonstrating effect of hole width at M=1.0

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Figure 8

Mainstream-jet interactions for (a) base line, (b) Case 3, and (c) Case 4 at M=1.0

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Figure 9

Detailed heat transfer coefficient ratio distributions for all cases at different blowing ratios

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Figure 10

Vorticity contours downstream of injection x∕D=3 for base line, Case 3, and Case 4

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Figure 11

Effect of hole configuration on spanwise averaged film effectiveness distributions at each blowing ratio

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Figure 12

Effect of hole configuration on spanwise averaged heat transfer coefficient ratio distributions at each blowing ratio

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Figure 13

Effect of blowing ratio on overall area-averaged (a) film effectiveness, and (b) heat transfer coefficient ratios for all cases

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Figure 14

Effect of blowing ratio on overall heat flux ratio for different cases

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