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Research Papers

Film Cooling Measurements for Cratered Cylindrical Inclined Holes

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

Mechanical Engineering, Virginia Tech, Blacksburg, VA 24061

Srinath V. Ekkad

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

Ronald S. Bunker

 GE Global Research Center, Niskayuna, NY 12301

J. Turbomach 131(1), 011005 (Oct 02, 2008) (12 pages) doi:10.1115/1.2950055 History: Received June 11, 2007; Revised June 21, 2007; Published October 02, 2008

Film cooling performance is studied for cylindrical holes embedded in craters. Different crater geometries are considered for a typical crater depth. Cratered holes may occur when blades are coated with thermal barrier coating layers by masking the hole area during thermal barrier coating (TBC) spraying, resulting in a hole surrounded by a TBC layer. The film performance and behavior is expected to be different for the cratered holes compared to standard cylindrical holes. 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 cooling effectiveness is slightly enhanced by cratering of holes, but a substantial increase in heat transfer enhancement negates the benefits of higher film effectiveness. Three different crater geometries are studied and compared to a base line flush cylindrical hole, a trenched hole, and a typical diffuser shaped hole. Computational fluid dynamics simulation using FLUENT was also performed to determine the jet-mainstream interactions associated with the experimental surface measurements.

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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 for base line holes

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Figure 4

All 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

Mainstream-jet interactions for (a) the base line, (b) Case 1, (c) Case 2, and (d) Case 3

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Figure 8

Computed nondimensional temperature contours of the film temperature (θ) and mixing downstream of the holes

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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 (1∕s) downstream of injection for (a) the base line, (b) Case 1, (c) Case 2, and (d) Case 3

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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 the overall heat flux ratio for different cases

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