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Research Papers

Measurements in Film Cooling Flows With Periodic Wakes

[+] Author and Article Information
Kristofer M. Womack

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

Ralph J. Volino

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

Michael P. Schultz

 Naval Architecture and Ocean Engineering Department, United States Naval Academy, Annapolis, MD 21402

J. Turbomach 130(4), 041008 (Jul 31, 2008) (13 pages) doi:10.1115/1.2812334 History: Received June 06, 2007; Revised June 22, 2007; Published July 31, 2008

Film cooling flows subject to periodic wakes were studied experimentally. The wakes were generated with a spoked wheel upstream of a flat plate. Cases with a single row of cylindrical film cooling holes inclined at 35deg to the surface were considered at blowing ratios of 0.25, 0.50, and 1.0 with a steady freestream and with wake Strouhal numbers of 0.15, 0.30, and 0.60. Temperature measurements were made using an infrared camera, thermocouples, and constant current (cold-wire) anemometry. Hot-wire anemometry was used for velocity measurements. The local film cooling effectiveness and heat transfer coefficient were determined from the measured temperatures. Phase locked flow temperature fields were determined from cold-wire surveys. Wakes decreased the film cooling effectiveness for blowing ratios of 0.25 and 0.50 when compared to steady freestream cases. In contrast, effectiveness increased with Strouhal number for the 1.0 blowing ratio cases, as the wakes helped mitigate the effects of jet lift-off. Heat transfer coefficients increased with wake passing frequency, with nearly the same percentage increase in cases with and without film cooling. The time resolved flow measurements show the interaction of the wakes with the film cooling jets. Near-wall flow measurements are used to infer the instantaneous film cooling effectiveness as it changes during the wake passing cycle.

Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Wind tunnel configuration: (a) schematic, (b) photograph of test wall with sidewalls, and (c) photograph looking upstream at rod moving across main flow

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Figure 2

Mean and fluctuating streamwise velocity upstream of film cooling holes, before installation of wake generator and during undisturbed phase of cycle with Sr=0.15

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Figure 3

Phase averaged U∕U∞ at x∕D=0, Sr=0.15

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Figure 4

Phase averaged u′∕U∞ at x∕D=0, Sr=0.15

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Figure 5

Phase averaged u′∕U∞ at x∕D=0, y∕D=0.01 and 1.5 for Sr=0.15, 0.30, and 0.60

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Figure 6

Film cooling effectiveness contours around center hole at various B (columns) and Sr (rows)

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Figure 7

Film cooling effectiveness for B=0.25 cases at various Sr; (a) centerline and (b) spanwise averaged

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Figure 8

Film cooling effectiveness for B=0.5 cases at various Sr; (a) centerline and (b) spanwise averaged

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Figure 9

Film cooling effectiveness for B=1.0 cases at various Sr; (a) centerline and (b) spanwise averaged

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Figure 10

Stanton numbers for cases without film cooling at various Sr

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Figure 11

Stanton number ratio, Stf∕Sto, contours around center hole at various B (columns) and Sr (rows)

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Figure 12

Stanton number ratio, Stf∕Sto, for B=0.25 cases at various Sr; (a) centerline and (b) spanwise averaged

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Figure 13

Stanton number ratio, Stf∕Sto, for B=0.5 cases at various Sr; (a) centerline and (b) spanwise averaged

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Figure 14

Stanton number ratio, Stf∕Sto, for B=1.0 cases at various Sr; (a) centerline and (b) spanwise averaged

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Figure 15

Heat flux ratio, q″f∕q″o, contours around center hole at various B (columns) and Sr (rows)

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Figure 16

Dimensionless temperature field, ϕ, for steady Sr=0 cases; upper image shows temperature contours in various planes, lower image shows isothermal surface with ϕ=0.3; (a) B=0.25, (b) B=0.5, and (c) B=1.0

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Figure 17

Dimensionless temperature field at various phases for B=0.5, Sr=0.15 case

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Figure 18

Dimensionless temperature field at various phases for B=1.0, Sr=0.15 case

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Figure 19

Dimensionless temperature field at various phases for B=0.5, Sr=0.30 case

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Figure 20

Dimensionless temperature field at various phases for B=1.0, Sr=0.30 case

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Figure 26

Phase averaged η* for B=0.5, Sr=0.60 case; (a) centerline and (b) spanwise average

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Figure 27

Phase averaged η* for B=1.0, Sr=0.60 case; (a) centerline and (b) spanwise average

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Figure 28

Phase averaged η* in wakes, between wakes, time mean of all phases, and corresponding η for B=0.5 cases; (a) centerline and (b) spanwise average

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Figure 25

Phase averaged η* for B=1.0, Sr=0.15 case; (a) centerline and (b) spanwise average

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Figure 24

Phase averaged η* for B=0.5, Sr=0.15 case; (a) centerline and (b) spanwise average

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Figure 23

Film cooling effectiveness, η (lower half of plot), and time averaged approximate effectiveness, η* (upper half of plot), for B=0.5, Sr=0.30 case

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Figure 22

Dimensionless temperature field at various phases for B=1.0, Sr=0.60 case

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Figure 21

Dimensionless temperature field at various phases for B=0.5, Sr=0.60 case

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