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Research Papers: Jets, Wakes, and Impingment Cooling

Film Cooling and Heat Transfer on Two Cutback Trailing Edge Models With Internal Perforated Blockages

[+] Author and Article Information
Jung-ho Choi, Shantanu Mhetras, Sai C. Lau

Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843-3123

Je-Chin Han

Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843-3123jc-han@tamu.edu

Ron Rudolph

 Siemens Power Generation, Inc., 1680 South Central Boulevard, Jupiter, FL 33458

J. Heat Transfer 130(1), 012201 (Jan 25, 2008) (13 pages) doi:10.1115/1.2780174 History: Received January 11, 2006; Revised March 21, 2007; Published January 25, 2008

Experiments to study heat transfer and film cooling on the cutback trailing edge of a turbine blade with slot ejection were performed. Heat transfer from two rows of perforated blockage inserts for lateral impingement on the coolant channel walls prior to coolant ejection into the freestream was also investigated. The internal test geometry is similar to the crossover impingement hole design used in modern gas turbine blades for trailing edge cooling. A liquid crystal technique based on hue value detection was used to measure the heat transfer coefficient on a trailing edge film-cooling model with slot ejection and an internal model with perforated blockage inserts. It was also used to determine the film effectiveness on the cutback trailing edge. For the internal model with the perforated blockage inserts, Reynolds numbers based on the hydraulic diameter of the slot and exit velocity were 5000, 10,000, 20,000, and 30,000 and corresponding coolant-to-freestream velocity ratios ranged from 0.26 to 1.83 for the external model with slot ejection, respectively. The experiments were performed for two different designs, 1 and 2, with Design 1 incorporating two different configurations with a staggered/inline slot exit arrangement and Design 2 with a staggered slot exit arrangement. Both designs utilized a 90deg flow turn into the blockage inserts as an entrance to the test section to simulate a realistic blade passage design. Results show that the internal design geometry of the trailing edge and Reynolds numbers can affect heat transfer in an internal model with perforated blockage inserts. Design 2 with a wider entrance channel and a sloped land near the ejection slots provided low heat transfer coefficients in the internal as well as external model but gave higher film-cooling effectiveness from slot ejection.

Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic drawing of a typical turbine blade with a cutback TE and impingement blockage inserts

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Figure 2

Schematic of the two TE models

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Figure 3

Schematic of wind tunnel and coolant flow loop

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Figure 4

Trailing edge test section placed in wind tunnel

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Figure 5

Three-dimensional, isometric view of Design 1 with a straight inlet and staggered rib separator configuration

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Figure 6

Test configuration matrix

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Figure 7

Spanwise pressure coefficient distribution for Configurations 1 and 3

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Figure 8

Effect of Reynolds number chamberwise averaged pressure coefficient distribution for all configurations

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Figure 9

Effect of configuration on chamberwise averaged pressure coefficients

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Figure 10

Internal heat transfer coefficients for Design 1 with a straight inlet and staggered slot arrangement (Configuration 1)

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Figure 11

Internal heat transfer coefficients for Design 2 with a straight inlet and staggered slot arrangement (Configuration 3)

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Figure 12

Spanwise averaged internal Nusselt numbers for all configurations

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Figure 13

Effect of configuration on chamberwise averaged internal Nusselt numbers

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Figure 14

Local Stanton number distribution on cutback slots and lands for Designs 1 and 2

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Figure 15

Spanwise averaged distributions of Stanton number on the cutback slots and lands for all configurations

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Figure 16

Effect of configuration on overall averaged Stanton number distributions

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Figure 17

Local film-cooling effectiveness distribution on cutback slots and lands for Designs 1 and 2

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Figure 18

Spanwise averaged film-cooling effectiveness distributions for the cutback slots, lands, and land and slot combined for all configurations

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Figure 19

Effect of configuration on overall averaged film-cooling effectiveness distributions on the cutback TE

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