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TECHNICAL PAPERS

Effect of Jet Pulsing on Film Cooling—Part I: Effectiveness and Flow-Field Temperature Results

[+] Author and Article Information
Sarah M. Coulthard

Department of Mechanical Engineering, Stanford University, Stanford, CA 94305

Ralph J. Volino

Department of Mechanical Engineering, United States Naval Academy, Annapolis, MD 21402volino@usna.edu

Karen A. Flack

Department of Mechanical Engineering, United States Naval Academy, Annapolis, MD 21402

J. Turbomach 129(2), 232-246 (May 31, 2006) (15 pages) doi:10.1115/1.2437231 History: Received May 25, 2006; Revised May 31, 2006

Pulsed film cooling was studied experimentally to determine its effect on film-cooling effectiveness. The film-cooling jets were pulsed using solenoid valves in the supply air line. Cases with a single row of cylindrical film-cooling holes inclined at 35 deg to the surface of a flat plate were considered at blowing ratios of 0.25, 0.5, 1.0, and 1.5 for a variety of pulsing frequencies and duty cycles. Temperature measurements were made using an infrared camera, thermocouples, and cold-wire anemometry. Hot-wire anemometry was used for velocity measurements. The local film-cooling effectiveness was calculated based on the measured temperatures, and the results were compared to baseline cases with continuous blowing. Phase-locked flow temperature fields were determined from cold-wire surveys. Pulsing at high frequencies helped to improve film-cooling effectiveness in some cases by reducing overall jet liftoff. At lower frequencies, pulsing tended to have the opposite effect. With the present geometry and a steady mainflow, pulsing did not provide an overall benefit. The highest overall effectiveness was achieved with continuous jets and a blowing ratio of 0.5. The present results may prove useful for understanding film-cooling behavior in engines, where mainflow unsteadiness causes film-cooling jet pulsation.

Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Wind tunnel configuration: (a) schematic and (b) photograph of test wall with sidewalls

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Figure 2

Time-averaged dimensionless temperature profile θ at exit plane of center hole with B=0.5, steady flow

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Figure 3

Time-averaged velocity profile, Ujet∕U∞, at exit plane of center hole with B=1.0, steady flow

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Figure 4

Time-averaged dimensionless flow temperature contours θ, in y-z plane for steady-flow cases at four blowing ratios (columns) and three streamwise locations (rows)

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Figure 5

Film-cooling effectiveness contours for steady blowing with B=0.25, 0.5, 1.0, and 1.5

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Figure 6

Film-cooling effectiveness for steady blowing cases: (a) centerline and (b) spanwise averaged; small symbols for present study, large symbols for data from literature

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Figure 7

Phase-averaged velocity profiles, Ujet∕U∞, at exit plane of center hole with B=0.5, F=0.0238, DC=0.5

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Figure 8

Phase-averaged velocity profiles, Ujet∕U∞, at exit plane of center hole with B=0.5, F=0.1905, DC=0.5

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Figure 9

Phase-averaged blowing ratio at various frequencies with nominal B=0.5, DC=0.5

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Figure 10

Phase-averaged dimensionless flow temperature contours θ in y-z plane: B=0.5, F=0.0238, DC=0.5: (a)x∕D=3.5, (b)x∕D=7, and (c)x∕D=14

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Figure 11

Film-cooling effectiveness contours at various pulsing frequencies with nominal B=0.5 and DC=0.5

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Figure 12

Film-cooling effectiveness for nominal B=0.5, DC=0.5 cases, with steady B=0.25 and B=0.5 cases included for comparison: (a) centerline and (b) spanwise averaged

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Figure 13

Phase-averaged blowing ratio at various frequencies with nominal B=1.0 and DC=0.5

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Figure 14

Phase-averaged dimensionless flow temperature contours θ in y-z plane: B=1.0, F=0.0238, DC=0.5: (a)x∕D=3.5, (b)x∕D=7, and (c)x∕D=14

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Figure 15

Phase-averaged dimensionless flow temperature contours θ in y-z plane: B=1.0, F=0.0476, DC=0.5, x∕D=3.5

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Figure 16

Phase-averaged dimensionless flow temperature contours θ in y-z plane: B=1.0, F=0.1905, DC=0.5: (a)x∕D=3.5, (b)x∕D=7, and (c)x∕D=14

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Figure 17

Film-cooling effectiveness contours at various pulsing frequencies with nominal B=1.0 and DC=0.5

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Figure 18

Film-cooling effectiveness for nominal B=1.0 and DC=0.5 cases, with steady B=0.5 and B=1.0 cases included for comparison: (a) centerline and (b) spanwise averaged

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Figure 19

Phase-averaged blowing ratio at various duty cycles with nominal B=0.5 and F=0.0238

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Figure 20

Film-cooling effectiveness contours at various duty cycles with nominal B=0.5 and F=0.0238

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Figure 21

Film-cooling effectiveness for nominal B=0.5 and F=0.0238 cases: (a) centerline and (b) spanwise averaged

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Figure 22

Phase-averaged blowing ratio at various duty cycles with nominal B=1.0 and F=0.0238

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Figure 23

Film-cooling effectiveness contours at various duty cycles with nominal B=1.0 and F=0.0238

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Figure 24

Film-cooling effectiveness for nominal B=1.0 and F=0.0238 cases: (a) centerline and (b) spanwise averaged

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Figure 25

Phase-averaged velocity profiles, Ujet∕U∞, at exit plane of center hole with B=1.0, F=0.1905, and DC=0.25

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Figure 26

Phase-averaged velocity profiles, Ujet∕U∞, at exit plane of center hole with B=1.0, F=0.1905, and DC=0.75

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Figure 27

Phase-averaged blowing ratio at various duty cycles with nominal B=1.0 and F=0.1905

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Figure 28

Film-cooling effectiveness contours at various duty cycles with nominal B=1.0 and F=0.1905

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Figure 29

Film-cooling effectiveness for nominal B=1.0 and F=0.1905 cases: (a) centerline and (b) spanwise averaged

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