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Research Papers

Effects of Surface Geometry on Film Cooling Performance at Airfoil Trailing Edge

[+] Author and Article Information
Akira Murata

Tokyo University of Agriculture and Technology, Koganei, Tokyo, 184 8588, Japanmurata@mmlab.mech.tuat.ac.jp

Satomi Nishida

Tokyo University of Agriculture and Technology, Koganei, Tokyo, 184 8588, Japan50009833204@st.tuat.ac.jp

Hiroshi Saito

Tokyo University of Agriculture and Technology, Koganei, Tokyo, 184 8588, Japansaito@mmlab.mech.tuat.ac.jp

Kaoru Iwamoto

Tokyo University of Agriculture and Technology, Koganei, Tokyo, 184 8588, Japaniwamotok@cc.tuat.ac.jp

Yoji Okita

IHI Corporation, Nishitama, Tokyo, 190 1297, Japanyouji_ookita@ihi.co.jp

Chiyuki Nakamata

IHI Corporation, Nishitama, Tokyo, 190 1297, Japanchiyuki_nakamata@ihi.co.jp

J. Turbomach 134(5), 051033 (May 31, 2012) (8 pages) doi:10.1115/1.4004828 History: Received July 12, 2011; Revised July 24, 2011; Published May 31, 2012; Online May 31, 2012

Cooling at the trailing edge of a gas turbine airfoil is one of the most difficult problems because of its thin shape, high thermal load from both surfaces, hard-to-cool geometry of narrow passages, and at the same time demand for structural strength. In this study, the heat transfer coefficient and film cooling effectiveness on the pressure-side cutback surface was measured by a transient infrared thermography method. Four different cutback geometries were examined: two smooth cutback surfaces with constant-width and converging lands (base and diffuser cases) and two roughened cutback surfaces with transverse ribs and spherical dimples. The Reynolds number of the main flow defined by the mean velocity and two times the channel height was 20,000, and the blowing ratio was varied among 0.5, 1.0, 1.5, and 2.0. The experimental results clearly showed spatial variation of the heat transfer coefficient and the film cooling effectiveness on the cutback and land top surfaces. The cutback surface results clearly showed periodically enhanced heat transfer due to the periodical surface geometry of ribs and dimples. Generally, the increase of the blowing ratio increased both the heat transfer coefficient and the film cooling effectiveness. Within the present experimental range, the dimple surface was a favorable cutback-surface geometry because it gave the enhanced heat transfer without deterioration of the high film cooling effectiveness.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Cutback film-cooling at airfoil trailing edge

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Figure 2

Schematic of experimental apparatus

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Figure 3

Details of test section

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Figure 4

Cross-sectional view of cutback part of base geometry

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Figure 5

Details of cutback surface and cooling flow slot for four different geometries examined in this study

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Figure 6

Streamwise variation of laterally averaged heat transfer coefficient and film cooling effectiveness: average was taken for cutback surface in (a) and (b) and for full span including land in (c). In (c), the lines without symbols are for the base case and thin to thick lines are corresponding to M = 0.5 to 2.0.

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Figure 7

Color contour of heat transfer coefficient and film cooling effectiveness of base geometry for M = 1.5

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Figure 8

Color contour of heat transfer coefficient and film cooling effectiveness of diffuser geometry for M = 1.5

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Figure 9

Streamwise variation of heat transfer coefficient and film cooling effectiveness: effect of blowing ratio for rib geometry on laterally averaged values

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Figure 10

Streamwise variation of heat transfer coefficient and film cooling effectiveness: effect of blowing ratio for dimple geometry

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Figure 11

Color contour of heat transfer coefficient and film cooling effectiveness of rib geometry for M = 1.5

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Figure 12

Color contour of heat transfer coefficient and film cooling effectiveness of dimple geometry for M = 1.5

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Figure 13

Streamwise variation of heat transfer coefficient and film cooling effectiveness: comparison of four different geometries for M = 1.5

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Figure 14

Cutback and land surface-averaged heat transfer coefficient and film cooling effectiveness (cutback and land surface-averages are shown with solid and broken lines, respectively)

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