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Research Papers

Bump and Trench Modifications to Film-Cooling Holes at the Vane-Endwall Junction

[+] Author and Article Information
N. Sundaram

Mechanical Engineering Department, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061nasundar@vt.edu

K. A. Thole

Mechanical and Nuclear Engineering Department, The Pennsylvania University, University Park, PA 16802

J. Turbomach 130(4), 041013 (Aug 01, 2008) (9 pages) doi:10.1115/1.2812933 History: Received June 06, 2007; Revised June 26, 2007; Published August 01, 2008

The endwall of a first-stage vane experiences high heat transfer and low adiabatic effectiveness levels because of high turbine operating temperatures and formation of leading edge vortices. These vortices lift the coolant off the endwall and pull the hot mainstream gases toward it. The region of focus for this study is the vane-endwall junction region near the stagnation location where cooling is very difficult. Two different film-cooling hole modifications, namely, trenches and bumps, were evaluated to improve the cooling in the leading edge region. This study uses a large-scale turbine vane cascade with a single row of axial film-cooling holes at the leading edge of the vane endwall. Individual hole trenches and row trenches were placed along the complete row of film-cooling holes. Two-dimensional semi-elliptically shaped bumps were also evaluated by placing the bumps upstream and downstream of the film-cooling row. Tests were carried out for different trench depths and bump heights under varying blowing ratios. The results indicated that a row trench placed along the row of film-cooling holes showed a greater enhancement in adiabatic effectiveness levels when compared to individual hole trenches and bumps. All geometries considered produced an overall improvement to adiabatic effectiveness levels.

Copyright © 2008 by American Society of Mechanical Engineers
Topics: Cooling , Coolants , Junctions
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References

Figures

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Figure 8

Contours of adiabatic effectiveness comparing the baseline case with the other configurations at a blowing ratio of M=2.0

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Figure 9

Laterally averaged adiabatic effectiveness comparing the effect of trenches and bumps at the leading edge at M=2.0

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Figure 10

Area-averaged effectiveness showing the effect of trenches and bumps on film-cooling effectiveness

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Figure 11

Area-averaged effectiveness showing the effect of different trench depths for the row trench configuration at varying blowing ratios

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Figure 12

Contours of adiabatic effectiveness showing the effect of varying the trench depth for the row trench configuration at three different blowing ratios

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Figure 13

Lateral averaged effectiveness showing the effect of the 0.8D trench depth at different blowing ratios

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Figure 14

Area-averaged effectiveness showing the effect of varying bump heights

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Figure 15

Contours of adiabatic effectiveness showing the effect of the 1.2D bumps at different blowing ratios

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Figure 16

Laterally averaged effectiveness showing the effect of the 1.2D bump at different blowing ratios

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Figure 17

Comparison of percent enhancement on area-averaged adiabatic effectiveness as a result of placing trenches at the leading edge

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Figure 18

Comparison of percent enhancement on area-averaged adiabatic effectiveness as a result of placing bumps at the leading edge

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Figure 19

Comparison of percent enhancement on area-averaged adiabatic effectiveness on trenches and bumps when compared to the baseline case at M=2.0

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Figure 1

Illustrates the endwall design studied at the leading edge

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Figure 2

Illustrates the (a) trench geometry and (b) bump geometry studied at the leading edge

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Figure 3

Schematic of the four configurations: (a) baseline, (b) individual trench, (c) row trench, and (d) bumps tested at the leading edge

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Figure 4

Illustration of the wind tunnel facility

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Figure 5

Contours of adiabatic effectiveness comparing the baseline case at different blowing ratios

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Figure 6

Lateral average effectiveness plots of the baseline case

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Figure 7

Area-averaged effectiveness for the baseline geometry along suction, pressure, and the whole leading edge region

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