Heat Transfer Measurements in a First-Stage Nozzle Cascade Having Endwall Contouring: Misalignment and Leakage Studies

[+] Author and Article Information
J. D. Piggush

Turbine Module Center, Pratt and Whitney, East Hartford, CTjustin.piggush@pw.utc.com

T. W. Simon

Heat Transfer Laboratory, Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455tsimon@me.umn.edu

J. Turbomach 129(4), 782-790 (Aug 11, 2006) (9 pages) doi:10.1115/1.2720506 History: Received July 23, 2006; Revised August 11, 2006

This work supports new gas turbine designs for improved performance by evaluating endwall heat transfer rates in a cascade that is representative of a first-stage stator passage and incorporates endwall assembly features and leakage. Assembly features, such as gaps in the endwall and misalignment of those gaps, disrupt the endwall boundary layer, typically leading to enhanced heat transfer rates. Leakage flows through such gaps within the passage can also affect endwall boundary layers and may induce additional secondary flows and vortex structures in the passage near the endwall. The present paper documents leakage flow and misalignment effects on the endwall heat transfer coefficients within a passage which has one axially contoured and one straight endwall. In particular, features associated with the combustor-to-turbine transition piece and the assembly joint on the vane platform are addressed.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 2

Schematic of the transition section slot geometry. Details are of the portion enclosed in the dashed square. Note that the dark gray portion indicates the heated sections of endwall and vane. The light gray piece was switched to create steps at the transition section slot.

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Figure 3

Schematic of the slashface slot geometry. The balsa insulation is included for the heat transfer studies.

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Figure 4

Typical boundary layer profiles. The profile on the left is approximately St×1000=5; on the right St×1000=10. The solid line is the gradient  ∣dT∕dn∣w, the dashed line is the calculated wall temperature, and the dot-dash line is the temperature measured when the thermocouple is on the wall. The intersection of the solid line and the dot-dash line occurs one thermocouple radius away from the wall.

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Figure 5

Nominal Stanton number×1000 distribution (a) and endwall surface temperatures (b)

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Figure 1

Schematic of test section

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Figure 6

Stanton number×1000 of the transition section forward facing step (a); transition section backward facing step (b); slashface forward facing step (c); and the slashface backward facing step (d)



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