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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July 2006
Technical Papers
Effect of Jet Pulsation and Duty Cycle on Film Cooling From a Single Jet on a Leading Edge Model
Srinath V. Ekkad,
Srinath V. Ekkad
Mem. ASME
Mechanical Engineering Department,
e-mail: ekkad@me.lsu.edu
Louisiana State University
, Baton Rouge, LA 70803
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Shichuan Ou,
Shichuan Ou
U.S. Air Force Research Laboratory
, Wright-Patterson AFB, OH 45433
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Richard B. Rivir
Richard B. Rivir
U.S. Air Force Research Laboratory
, Wright-Patterson AFB, OH 45433
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Srinath V. Ekkad
Mem. ASME
Mechanical Engineering Department,
Louisiana State University
, Baton Rouge, LA 70803e-mail: ekkad@me.lsu.edu
Shichuan Ou
U.S. Air Force Research Laboratory
, Wright-Patterson AFB, OH 45433
Richard B. Rivir
U.S. Air Force Research Laboratory
, Wright-Patterson AFB, OH 45433J. Turbomach. Jul 2006, 128(3): 564-571 (8 pages)
Published Online: January 25, 2006
Article history
Received:
January 4, 2005
Revised:
January 25, 2006
Citation
Ekkad, S. V., Ou, S., and Rivir, R. B. (January 25, 2006). "Effect of Jet Pulsation and Duty Cycle on Film Cooling From a Single Jet on a Leading Edge Model." ASME. J. Turbomach. July 2006; 128(3): 564–571. https://doi.org/10.1115/1.2185122
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