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TECHNICAL PAPERS

Adiabatic Effectiveness Measurements and Predictions of Leakage Flows Along a Blade Endwall

[+] Author and Article Information
W. W. Ranson, K. A. Thole

Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24060

F. J. Cunha

Pratt & Whitney, United Technologies Corporation, East Hartford, CT 06108

J. Turbomach 127(3), 609-618 (Jan 18, 2005) (10 pages) doi:10.1115/1.1929809 History: Received September 26, 2004; Revised January 18, 2005

Traditional cooling schemes have been developed to cool turbine blades using high-pressure compressor air that bypasses the combustor. This high-pressure forces cooling air into the hot main gas path through seal slots. While parasitic leakages can provide a cooling benefit, they also represent aerodynamic losses. The results from the combined experimental and computational studies reported in this paper address the cooling benefit from leakage flows that occur along the platform of a first stage turbine blade. A scaled-up, blade geometry with an upstream slot, a mid-passage slot, and a downstream slot was tested in a linear cascade placed in a low-speed wind tunnel. Results show that the leakage flow through the mid-passage gap provides only a small cooling benefit to the platform. There is little to no benefit to the blade platform that results by increasing the coolant flow through the mid-passage gap. Unlike the mid-passage gap, leakage flow from the upstream slot provides good cooling to the platform surface, particularly in certain regions of the platform. Relatively good agreement was observed between the computational and experimental results, although computations overpredicted the cooling.

Copyright © 2005 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of test section (thermal rake locations for Figs.  1011 indicated)

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Figure 2

Side view of backward facing step in the front slot, which contains the front gutter

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Figure 3

Schematic of linear blade cascade, including flexible walls and upstream normal jets

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Figure 4

Measured and predicted pressure distributions

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Figure 5

Adiabatic effectiveness measurements for 1.5% front slot and aft slot, and 0.25% featherseal flow

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Figure 6

Adiabatic effectiveness measurements for 1.5% front and aft slot flow with (a) 0.25%, (b) 0.5%, and (c) 0.75% featherseal flow

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Figure 7

Average adiabatic effectiveness measurements for the data shown in Figs.  666

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Figure 8

Adiabatic effectiveness measurements for 0.25% featherseal flow and 1.5% aft slot flow with (a) 1.5% front slot, (b) 2.0% front slot, and (c) 0.5% front slot flow

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Figure 9

Average adiabatic effectiveness measurements for the data shown in Figs.  888

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Figure 10

Thermal rake measurements along the leading edge of the featherseal with 1.5% front slot flow for (a) 0.25% featherseal and (b) 0.75% featherseal flow

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Figure 11

Thermal rake measurements along the trailing edge of the featherseal with 1.5% front slot flow for (a) 0.25% featherseal and (b) 0.75% featherseal flow

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Figure 12

Computational predictions for 1.5% front and aft slot flow and 0.25% featherseal flow

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Figure 13

Computational streamlines colored by height from the featherseal for 0.25% flow, with 1.5% front rim flow (not shown for clarity)

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Figure 14

Computational predictions for (a) 1.5% front slot and 0.25% featherseal, (b) 2.0% front slot and 0.25% featherseal, and (c) 2.0% front slot and 0.75% featherseal, all with 1.5% aft slot flow

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Figure 15

Average adiabatic effectiveness measurements for the experimental data and computational predictions

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