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Research Papers: Fuel Combustion

Numerical Predictions of Three-Dimensional Unsteady Turbulent Film-Cooling for Trailing Edge of Gas-Turbine Blade Using Large Eddy Simulation

[+] Author and Article Information
Ahmed Khalil, Hatem Kayed, Abdallah Hanafi

Mechanical Power Department,
Faculty of Engineering,
Cairo University,
Giza 12613, Egypt

Medhat Nemitallah

KACST TIC on CCS and Mechanical Engineering
Department,
King Fahd University of Petroleum and Minerals,
Dhahran 31261, Saudi Arabia
e-mail: medhatahmed@kfupm.edu.sa

Mohamed Habib

KACST TIC on CCS and Mechanical Engineering
Department,
King Fahd University of Petroleum and Minerals,
Dhahran 31261, Saudi Arabia

1Corresponding author.

Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received September 8, 2018; final manuscript received February 6, 2019; published online February 27, 2019. Assoc. Editor: Reza Sheikhi.

J. Energy Resour. Technol 141(4), 042206 (Feb 27, 2019) (12 pages) Paper No: JERT-18-1700; doi: 10.1115/1.4042824 History: Received September 08, 2018; Revised February 06, 2019

This work investigates the performance of film-cooling on trailing edge of gas turbine blades using unsteady three-dimensional numerical model adopting large eddy simulation (LES) turbulence scheme in a low Mach number flow regime. This study is concerned with the scaling parameters affecting effectiveness and heat transfer performance on the trailing edge, as a critical design parameter, of gas turbine blades. Simulations were performed using ANSYS-fluentworkbench 17.2. High quality mesh was adapted, whereas the size of cells adjacent to the wall was optimized carefully to sufficiently resolve the boundary layer to obtain insight predictions of the film-cooling effectiveness on a flat plate downstream the slot opening. Blowing ratio, density ratio, Reynolds number, and the turbulence intensity of the mainstream and coolant flow are optimally examined against the film-cooling effectiveness. The predicted results showed a great agreement when compared with the experiments. The results show a distinctive behavior of the cooling effectiveness with blowing ratio variation as it has a dip in vicinity of unity which is explained by the behavior of the vortex entrainment and momentum of coolant flow. The negative effect of the turbulence intensity on the cooling effectiveness is demonstrated as well.

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References

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Figures

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Fig. 1

Model geometry: (a) trailing edge cooling slots at pressure side breakout and (b) control volume around one slot opening

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Fig. 2

Snap shot of the meshed control volume

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Fig. 3

Velocity profiles for experimental work [23] and this study, BR =1.1, at x/H = 0.5, 2, and 8: (a) x/H = 2 and (b) x/H = 8

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Fig. 4

Mean film-cooling effectiveness contours on the cutback surface: (a) BR = 0.43, (b) BR = 0.76, (c) BR = 0.85, (d) BR = 1.1, (e) BR = 1.6, and (f) BR = 1.75

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Fig. 5

Mean span-averaged film-cooling effectiveness profiles in the slot centerline downstream the opening for different blowing ratios

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Fig. 6

Mean spanwise-averaged film-cooling effectiveness at (a) x/H = 8.0, (b)x/H = 6, and (c) x/H = 9

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Fig. 7

Contours of mean film-cooling effectiveness in the slot midplane perpendicular on the cutback surface

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Fig. 8

Velocity vector and vorticity fields

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Fig. 9

Density ratio effect on the span-averaged mean effectiveness: (a) BR = 0.43, (b) BR = 1.1, and (c) BR = 1.6

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Fig. 10

Reynolds number effect on the span-averaged mean effectiveness at constant BR: case (a) BR = 0.76, case (b) BR = 1.1, and case (c) BR = 1.6

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Fig. 11

Coolant flow turbulence intensity effect on the span-averaged mean effectiveness

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Fig. 12

Mainstream turbulence intensity effect on the span-averaged mean effectiveness

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Fig. 13

Mean span-averaged film-cooling effectiveness

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