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Research Papers

Computations of Turbulent Flow and Heat Transfer Through a Three-Dimensional Nonaxisymmetric Blade Passage

[+] Author and Article Information
Arun K. Saha, Sumanta Acharya

Turbine Innovation and Energy Research (TIER) Center, Louisiana State University, Baton Rouge, LA 70803

J. Turbomach 130(3), 031008 (May 02, 2008) (10 pages) doi:10.1115/1.2776952 History: Received October 08, 2006; Revised May 31, 2007; Published May 02, 2008

The design of a three-dimensional nonaxisymmetric end wall is carried out using three-dimensional numerical simulations. The computations have been conducted both for the flat and contoured end walls. The performance of the end wall is evaluated by comparing the heat transfer and total pressure loss reduction. The contouring is done in such a way to have convex curvature in the pressure side and concave surface in the suction side. The convex surface increases the velocity by reducing the local static pressure, while the concave surface decreases the velocity by increasing the local pressure. The profiling of the end wall is done by combining two curves, one that varies in the streamwise direction, while the other varies in the pitchwise direction. Several contoured end walls are created by varying the streamwise variation while keeping the pitchwise curve constant. The flow near the contoured end wall is seen to be significantly different from that near the flat end wall. The contoured end wall is found to reduce the secondary flow by decreasing radial pressure gradient. The total pressure loss is also lower and the average heat transfer reduces by about 8% compared to the flat end wall. Local reductions in heat transfer are significant (factor of 3). This study demonstrates the potential of three-dimensional end-wall contouring for reducing the thermal loading on the end wall.

Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Flow model and the confining boundaries

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Figure 2

The distribution used in (a) streamwise and (b) pitchwise directions to generate the end wall

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Figure 3

(a) Contours of the end-wall height in meters and (b) three-dimensional view of the end wall

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Figure 4

(a) Three-dimensional view of the grid on the confining boundaries, (b) grid used on the end walls, and (c) a close-up view of the grid near the end-wall–blade junction

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Figure 5

(a) Plane along which the line plots of Nusselt number and static pressure coefficient versus transverse distance in (b) and (c) are drawn. Note that Y∕P=0 represents the intersection of the axial chord line shown with the pressure surface. Y∕P>0 represents the pressure side.

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Figure 6

Grid independence study showing contours of Nusselt number on the end wall using two grids: (a) size=927,320 (coarse) and (b) size=2,204,688 (fine)

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Figure 7

Static pressure coefficient on both the blade and end wall: (a) flat end wall and (b) contoured end wall

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Figure 8

Contours of the static pressure coefficient on the bottom wall: (a) flat and (b) contoured end walls. (c) Line plot at 15% of the Cx. Note that Y∕P=0 represents the intersection of the 15% axial chord line with the pressure surface. Y∕P>0 represents the pressure side.

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Figure 9

Surface streamlines on the end wall: (a) flat and (b) contoured end walls

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Figure 10

Three-dimensional pathlines near the end wall: (a) flat and (b) contoured end walls

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Figure 11

Streamtraces superimposed on the contours of nondimensional streamwise vorticity at 20% of the axial chord: (a) base line (flat end wall) and (b) contoured end wall

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Figure 12

Streamtraces superimposed on the contours of nondimensional streamwise vorticity at 80% of the axial chord: (a) base line (flat end wall) and (b) contoured end wall

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Figure 13

Contours of total pressure loss coefficient at 120% of the axial chord: (a) base line (flat end wall) and (b) contoured end wall

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Figure 14

Contours of the Nusselt number on the bottom wall: (a) flat and (b) contoured end walls

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Figure 15

Variation of Nusselt number along axial chord lines 1 and 2 shown in (a). In (b), Nu is shown along line 1. In (c), Nu is shown along line 2.

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