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Research Papers

Heat Transfer for a Turbine Blade With Nonaxisymmetric Endwall Contouring

[+] Author and Article Information
Stephen P. Lynch, Narayan Sundaram, Karen A. Thole

Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, PA 16802

Atul Kohli, Christopher Lehane

 Pratt & Whitney, 400 Main Street, East Hartford, CT 06108

J. Turbomach 133(1), 011019 (Sep 23, 2010) (9 pages) doi:10.1115/1.4000542 History: Received July 06, 2009; Revised July 25, 2009; Published September 23, 2010; Online September 23, 2010

Complex vortical secondary flows that are present near the endwall of an axial gas turbine blade are responsible for high heat transfer rates and high aerodynamic losses. The application of nonaxisymmetric, three-dimensional contouring to the endwall surface has been shown to reduce the strength of the vortical flows and decrease total pressure losses when compared with a flat endwall. The reduction in secondary flow strength with nonaxisymmetric contouring might also be expected to reduce endwall heat transfer. In this study, measurements of endwall heat transfer were taken for a low-pressure turbine blade geometry with both flat and three-dimensional contoured endwalls. Endwall oil flow visualization indicated a reduction in the passage vortex strength for the contoured endwall geometry. Heat transfer levels were reduced by 20% in regions of high heat transfer with the contoured endwall, as compared with the flat endwall. The heat transfer benefit of the endwall contour was not affected by changes in the cascade Reynolds number.

Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Depiction of the (a) large-scale low-speed wind tunnel with a corner test section housing the Pack-B cascade and (b) the inlet flow development section

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Figure 2

Schematic of the blade cascade with heat flux plates on the endwall (a), isometric view of the contoured endwall (b), and the contoured endwall heater mounted on a thin stereolithography plate (c)

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Figure 3

Inlet turbulent boundary layer measured 2.85Cax upstream of blade 4 (see Fig. 2) with and without the turbulence grid installed

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Figure 4

Heat transfer coefficient development along a line approaching blade 4 (see Fig. 2) with the turbulence grid installed

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Figure 5

Freestream turbulence decay downstream of the turbulence grid measured along the midspan centerline of the tunnel

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Figure 6

Blade static pressure distribution at the midspan plane for the flat and contoured endwalls

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Figure 7

Qualitative interpretation of endwall streaklines from oil flow visualization on the (a) flat endwall and (b) contoured endwall

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Figure 8

Contours of endwall Nusselt number for the flat endwall

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Figure 9

Nusselt numbers for the flat endwall plotted along inviscid streamlines passing through 0.25P, 0.50P, and 0.75P (see inset)

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Figure 10

Nusselt numbers for the flat endwall plotted along pitchwise lines at 0.25Cax, 0.75Cax, and 1.25Cax from the leading edge (see inset)

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Figure 11

Contours of heat transfer coefficient augmentation for the flat versus contoured endwalls

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Figure 12

Heat transfer coefficient augmentation along inviscid streamline paths (see Fig. 9)

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Figure 13

Heat transfer coefficient augmentation along pitchwise lines (see Fig. 1)

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Figure 14

Contours of Nusselt number for the flat endwall at (a) Reexit=118,000, (b) Reexit=200,000 (nominal), and (c) Reexit=307,000

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Figure 15

Contours of heat transfer augmentation for (a) Reexit=118,000, (b) Reexit=200,000 (nominal), and (c) Reexit=307,000

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Figure 16

Contoured versus flat endwall heat transfer augmentation at various cascade exit Reynolds numbers, plotted along the inviscid streamlines passing through (a) 0.25P, (b) 0.50P, and (c) 0.75P (see inset)

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