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Research Papers

The Effect of Combustor-Turbine Interface Gap Leakage on the Endwall Heat Transfer for a Nozzle Guide Vane

[+] Author and Article Information
S. P. Lynch

Mechanical Engineering Department, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061

K. A. Thole

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

J. Turbomach 130(4), 041019 (Aug 04, 2008) (10 pages) doi:10.1115/1.2812950 History: Received June 15, 2007; Revised June 26, 2007; Published August 04, 2008

To enable turbine components to withstand high combustion temperatures, they are cooled by air routed from the compressor, which can leak through gaps between components. These gaps vary in size from thermal expansions that take place. The leakage flow between the interface of the combustor and the turbine, in particular, interacts with the flowfield along the endwall. This study presents measurements of adiabatic cooling effectiveness and heat transfer coefficients on the endwall of a first vane, with the presence of leakage flow through a flush slot upstream of the vane. The effect of axial contraction of the slot width due to thermal expansion of the engine was tested for two blowing rates. Contracting the slot width, while maintaining the slot mass flow, resulted in a larger coolant coverage area and higher effectiveness values, as well as slightly lower heat transfer coefficients. Matching the momentum flux ratio of the leakage flow from the nominal and contracted slot widths lowered both cooling effectiveness and heat transfer coefficients for the contracted slot flow. Comparison of the coolant coverage pattern to the measured endwall shear stress topology indicated that the trajectory of the slot coolant was dictated by the complex endwall flow.

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Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Large low-speed wind tunnel with separate flow conditioning paths and corner test section

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Figure 2

A schematic of the endwall and the combustor-turbine leakage interface (upstream slot) modeled in this study

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Figure 3

Example of oil film interferograms on nickel foil, used to determine endwall friction coefficient magnitude and direction

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Figure 4

Measured friction coefficient vectors for no upstream slot flow, which illustrate the features of secondary flow over the endwall

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Figure 5

Endwall limiting streamlines and the separation line calculated from the friction coefficient vectors in Fig. 4, with inviscid streamlines from FLUENT (21) overlaid

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Figure 6

Contours of endwall effectiveness from upstream slot flow for (a) nominal slot, MFR=0.5%; (b) half slot, MFR=0.5%; (c) nominal slot, MFR=1.0%; and (d) half slot, MFR=1.0%

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Figure 7

Adiabatic cooling effectiveness on the endwall from upstream slot flow, sampled along an inviscid streamline released from (a) 25% pitch, (b) 50% pitch, and (c) 75% pitch

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Figure 8

Contours of effectiveness for the nominal slot at 1.0% MFR for (a) Knost and Thole (10) (slot at X∕Cax=−0.38), and (b) this study (slot at X∕Cax=−0.77)

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Figure 9

Contours of St for (a) Kang (5) (no upstream slot); (b) base line (no upstream slot); (c) nominal slot, MFR=0.5%; (d) half slot, MFR=0.5%; (e) nominal slot, MFR=1.0%; and (f) half slot, MFR=1.0%

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Figure 10

Heat transfer augmentation on the endwall from upstream slot flow, sampled along an inviscid streamline released from (a) 25% pitch, (b) 50% pitch, and (c) 75% pitch

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Figure 11

NHFR to the endwall from upstream slot flow, sampled along an inviscid streamline released from (a) 25% pitch, (b) 50% pitch, and (c) 75% pitch

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Figure 12

Area-averaged NHFR to the endwall as a function of upstream slot momentum flux ratio

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