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TECHNICAL PAPERS

Effect of Jet Pulsation and Duty Cycle on Film Cooling From a Single Jet on a Leading Edge Model

[+] Author and Article Information
Srinath V. Ekkad1

Mechanical Engineering Department, Louisiana State University, Baton Rouge, LA 70803ekkad@me.lsu.edu

Shichuan Ou, Richard B. Rivir

 U.S. Air Force Research Laboratory, Wright-Patterson AFB, OH 45433

1

To whom correspondence should be addressed.

J. Turbomach 128(3), 564-571 (Jan 25, 2006) (8 pages) doi:10.1115/1.2185122 History: Received January 04, 2005; Revised January 25, 2006

The effect of jet pulsation and duty cycle on film effectiveness and heat transfer was investigated on a film hole located on the circular leading edge of a blunt body. A transient infrared technique was used to measure both heat transfer coefficients and film effectiveness from a single test. Detailed Frossling number and film effectiveness distributions were obtained for all flow conditions. Jet pulsing frequencies of 5 Hz, 10 Hz, and 20 Hz have been studied. The effect of duty cycle created by the valve opening and closing times was also set at different levels of 10%, 25%, 50%, and 75% of designated 100% fully open condition for different blowing ratios from 0.25 to 2.0. The combination of pulse frequency and duty cycle was investigated for different blowing ratios on a single leading edge hole located at 22 deg from geometric leading edge. Results indicate that higher effectiveness and lower heat transfer coefficients are obtained at the reduced blowing ratios, which result from reduced duty cycles. The effect of varying the pulsing frequency from 5 Hz to 20 Hz is not discernable beyond the level of experimental uncertainty. Effective blowing ratio due to lowering of the duty cycle at a given blowing ratio seems to play a more important role in combination with pulsing, which provides improved cooling effectiveness at lower heat transfer coefficients.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of test facility

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Figure 2

Illustration of the opened out view of the leading edge test model with open hole and plugged hole locations

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Figure 3

Temperature response of different thermocouples in degrees celsius

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Figure 4

Effect of blowing ratio on spanwise-averaged Nusselt number distribution for an unpulsed jet

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Figure 5

Effect of blowing ratio on spanwise-averaged film effectiveness distribution for an unpulsed jet

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Figure 6

Effect of pulsing frequency and duty cycle on Frossling number distributions

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Figure 7

Effect of pulsing frequency and duty cycle on film effectiveness distributions

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Figure 8

Effect of pulsing frequency on Nusselt number for a particular effective blowing ratio

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Figure 9

Effect of pulsing frequency on film effectiveness for a particular effective blowing ratio

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