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Research Papers

A Comparison of Cylindrical and Fan-Shaped Film-Cooling Holes on a Vane Endwall at Low and High Freestream Turbulence Levels

[+] Author and Article Information
W. Colban

Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94551-0969wcolban@sandia.gov

K. A. Thole

Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802-1412kthole@psu.edu

M. Haendler

 Siemens Power Generation, Muelheim a. d., Ruhr, Germany

J. Turbomach 130(3), 031007 (May 02, 2008) (9 pages) doi:10.1115/1.2720493 History: Received July 14, 2006; Revised July 26, 2006; Published May 02, 2008

Fan-shaped film-cooling holes have been shown to provide superior cooling performance to cylindrical holes along flat plates and turbine airfoils over a large range of different conditions. Benefits of fan-shaped holes include less required cooling air for the same performance, increased part lifetime, and fewer required holes. The major drawback, however, is increased manufacturing cost and manufacturing difficulty, particularly for the vane platform region. To this point, there have only been extremely limited comparisons between cylindrical and shaped holes on a turbine endwall at either low or high freestream turbulence conditions. This study presents film-cooling effectiveness measurements on an endwall surface in a large-scale, low-speed, two-passage, linear vane cascade. Results showed that film-cooling effectiveness decreased with increasing blowing rate for the cylindrical holes, indicating jet liftoff. However, the fan-shaped passage showed increased film-cooling effectiveness with increasing blowing ratio. Overall, fan-shaped holes increased film-cooling effectiveness by an average of 75% over cylindrical holes for constant cooling flow.

Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of the low-speed recirculating wind tunnel facility

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Figure 2

Static pressure distribution around the center vane

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Figure 3

Film-cooling hole layout and specifications

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Figure 4

Contours of calculated (a) blowing ratio and (b) momentum flux ratio for the baseline conditions

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Figure 5

Effectiveness contours at low freestream turbulence for the cylindrical passage (ac) and fan-shaped passage (df)

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Figure 6

Effectiveness contours at high freestream turbulence for the cylindrical passage (ac) and fan-shaped passage (df)

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Figure 7

Laterally averaged effectiveness for the 100% baseline case and augmentation of laterally averaged effectiveness for the 75% and 125% cases on the cylindrical passage at low freestream turbulence

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Figure 8

Closeup view of region near the pressure side leading edge (baseline 100% case)

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Figure 9

Laterally averaged effectiveness for the 100% baseline case and augmentation of laterally averaged effectiveness for the 75% and 125% cases on the fan-shaped passage at low freestream turbulence

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Figure 10

Augmentation of laterally averaged film-cooling effectiveness for fan-shaped cooling holes over cylindrical cooling holes

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Figure 11

Augmentation of laterally averaged film-cooling effectiveness for the cylindrical passage at high freestream turbulence

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Figure 12

Augmentation of laterally averaged film-cooling effectiveness for the fan-shaped passage at high freestream turbulence

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Figure 13

Effectiveness along the data line shown in Fig. 3 for each baseline case

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Figure 14

Effectiveness along a streamline released from 40% pitch for each baseline case

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Figure 15

Effectiveness along a streamline released from 80% pitch for each baseline case

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Figure 16

Area-averaged film-cooling effectiveness for all cases

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