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Research Papers

Effect of Pulsed Film Cooling on Leading Edge Film Effectiveness

[+] Author and Article Information
Lamyaa A. El-Gabry

Department of Mechanical Engineering, The American University in Cairo, New Cairo 11835, Egyptlelgabry@aucegypt.edu

Richard B. Rivir

Air Force Research Laboratory, Propulsion Directorate, Wright-Patterson AFB, OH 45433richard.rivir@wpafb.af.mil

J. Turbomach 134(4), 041005 (Jul 19, 2011) (6 pages) doi:10.1115/1.4003653 History: Received August 02, 2010; Revised August 10, 2010; Published July 19, 2011; Online July 19, 2011

Detailed film effectiveness measurements have been made on a cylindrical leading edge surface for steady and pulsating flows. The film hole is off centered by 21.5 deg from the centerline and angled 20 deg to the surface and 90 deg from the streamwise direction. Two jet-to-cross-flow velocity ratios have been considered: VR=1 and 2, which correspond to blowing ratios of 1 and 2, respectively. The pulsating frequency is 10 Hz and the duty cycle is 50%. Comparisons between film effectiveness with a pulsating film and a continuous film show that for the same blowing ratio, the effectiveness of the film drops by a factor of 2 when the flow is pulsed. Hotwire measurements are made to characterize the pulsating velocity waveform at the exit of the film exit and verify the integrity of the pulse. The variation in the measured surface adiabatic wall temperature over the pulsing duration is very small, suggesting a large thermal inertia that keeps the wall surface largely unaffected by the time scale of the pulsations; this holds true for both blowing ratios tested.

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Figures

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Figure 1

Experimental apparatus

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Figure 2

Blowing ratio pulse waveform

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Figure 3

Variation of raw IR temperature data over duration of one pulse period

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Figure 4

Adiabatic film effectiveness distribution (VR=2)

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Figure 5

Adiabatic film effectiveness distribution (VR=1)

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Figure 6

Local film effectiveness at discrete streamwise locations for VR=2

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Figure 7

Local film effectiveness at discrete streamwise locations for VR=1

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Figure 8

Span-averaged film effectiveness

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Figure 9

Comparison with Ekkad (15) for M=1

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Figure 10

Comparison with Ekkad (15) for M=2

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Figure 11

Results only of Ekkad (15) to compare effect of pulsing

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