Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

Minimization of Heat Load Due to Secondary Reactions in Fuel Rich Environments

[+] Author and Article Information
Andrew T. Shewhart, Jacob J. Robertson, Nathan J. Greiner, James L. Rutledge

Air Force Institute of Technology,
WPAFB, OH 45433

Marc D. Polanka

Air Force Institute of Technology,
WPAFB, OH 45433
e-mail: Marc.Polanka@afit.edu

1Corresponding author.

Contributed by the Heat Transfer Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received March 31, 2015; final manuscript received April 23, 2015; published online June 2, 2015. Editor: David Wisler. This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. Approved for public release; distribution is unlimited.

J. Eng. Gas Turbines Power 137(12), 121504 (Jun 02, 2015) (10 pages) Paper No: GTP-15-1114; doi: 10.1115/1.4030520 History: Received March 31, 2015

The demand for increased thrust, higher engine efficiency, and reduced fuel consumption has increased the turbine inlet temperature and pressure in modern gas turbine engines. The outcome of these higher temperatures and pressures is the potential for unconsumed radical species to enter the turbine. Because modern cooling schemes for turbine blades involve injecting cool, oxygen-rich air adjacent to the surface, the potential for reaction with radicals in the mainstream flow, and augmented heat transfer to the blade arises. This result is contrary to the purpose of film cooling. In this environment, there is a competing desire to consume any free radicals prior to the flow entering the rotor stage while still maintaining surface temperatures below the metal melting temperature. This study evaluated various configurations of multiple cylindrical rows of cooling holes in terms of both heat release and effective downstream cooling. Results were evaluated based on net heat flux reduction (NHFR) and a new wall absorption (WA) parameter which combined the additional heat available from these secondary reactions with the length of the resulting flame to determine which schemes protected the wall more efficiently. Two particular schemes showed promise. The two row upstream configuration reduced the overall augmentation of heat by creating a short, concentrated reaction area. Conversely, the roll forward configuration minimized the local heat flux enhancement by spreading the reaction area over the surface being cooled.

Copyright © 2015 by ASME
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Fig. 1

Experimental setup for acquiring heat flux measurements of reacting film-cooling air

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Fig. 2

Details of test section

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Fig. 3

Heat transfer thermocouple pairs locations

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Fig. 4

Film-cooling geometries (millimeters)

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Fig. 5

Single row—heat flux versus blowing ratio, x/D = 17 and φ = 1.175

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Fig. 6

Wall temperature effects on augmentation

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Fig. 7

Single row—augmentation versus blowing ratio, φ = 1.175

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Fig. 8

Single row—enhanced flame image, φ = 1.175 and M = 2.0

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Fig. 9

Single row—augmentation versus equivalence ratio: solid symbols are for M = 1 and open symbols represent M = 2

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Fig. 10

Five row—augmentation versus blowing ratio, ϕ = 1.175

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Fig. 11

Five row—enhanced flame image, φ = 1.175 and M = 2.0

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Fig. 12

Five row—air cooled emissions span, φ = 1.175 and M = 2.0

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Fig. 13

Five row—augmentation versus φ, M = 2.0

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Fig. 14

Configuration comparison—augmentation versus blowing ratio at x/D = 22 and φ = 1.175

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Fig. 15

Configuration comparison—augmentation versus downstream distance, φ = 1.175 and M = 2.0

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Fig. 16

Configuration comparison—augmentation versus φ at x/D = 22 and M = 2.0

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Fig. 17

Enhanced flame images comparison, φ = 1.175 and M = 2.0. (a) Single row, (b) five row, (c) roll forward, and (d) two row upstream.

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Fig. 18

Configuration comparison—% volume of CO, air cooling, φ = 1.175 and M = 2.0

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Fig. 19

Configuration comparison—NHFR—nitrogen as coolant, x/D = 17

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Fig. 20

Configuration comparison—NHFR—air as coolant, x/D = 17




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