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Research Papers

Combined Effects of Wakes and Jet Pulsing on Film Cooling

[+] 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), 041010 (Aug 01, 2008) (12 pages) doi:10.1115/1.2812335 History: Received June 06, 2007; Revised June 22, 2007; Published August 01, 2008

Pulsed film cooling jets 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 B of 0.50 and 1.0 with jet pulsing and wake Strouhal numbers of 0.15, 0.30, and 0.60. Wake timing was varied with respect to the pulsing. Temperature measurements were made using an infrared camera, thermocouples, and constant current (cold wire) anemometry. 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. With B=0.5, wakes and pulsing both lead to a reduction in film cooling effectiveness, and the reduction is larger when wakes and pulsing are combined. With B=1.0, pulsing again causes a reduction in effectiveness, but wakes tend to counteract this effect somewhat by reducing jet lift-off. At low Strouhal numbers, wake timing had a significant effect on the instantaneous film cooling effectiveness, but wakes in general had very little effect on the time averaged effectiveness. At high Strouhal numbers, the wake effect was stronger, but the wake timing was less important. Wakes increased the heat transfer coefficient strongly and similarly in cases with and without film cooling, regardless of wake timing. Heat transfer coefficient ratios, similar to the time averaged film cooling effectiveness, did not depend strongly on wake timing for the cases considered.

Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 16

Phase averaged η* for B=1.0, Sr=0.15; (a) P/NW, (b) P/WO, (c) P/WI

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Figure 21

Time averaged centerline η and η* for B=1.0, Sr=0.30

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Figure 27

Centerline Stanton number ratio, Stf∕Sto, for B=1.0, Sr=0.60 cases

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Figure 12

Time averaged centerline η and η* for B=0.5, Sr=0.60

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Figure 13

Phase averaged centerline η* for B=0.5, Sr=0.60

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Figure 1

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

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Figure 2

Dimensionless temperature field, ϕ, for B=0.5, Sr=0.15, upper image shows temperature contours in various planes, color range 0 (blue) to 0.6 (red); lower image shows isothermal surface with ϕ=0.3; axis limits: x=−1.74D to 12D, z=−1.5D to 1.5D, y=0 to 2.55D; (a) P/NW, (b) P/WO, (c) P/WI (see Table 1 for names)

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Figure 14

Centerline Stanton number ratio, Stf∕Sto, for B=0.5, Sr=0.60

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Figure 15

Dimensionless temperature field, ϕ for B=1.0, Sr=0.15; (a) P/NW, (b) P/WO, (c) P/WI

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Figure 3

Phase averaged η* for B=0.5, Sr=0.15, white lines indicate wake duration in freestream (solid) and near-wall (dashed); (a) P/NW, (b) P/WO, (c) P/WI

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Figure 17

Time averaged centerline η and η* for B=1.0, Sr=0.15

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Figure 18

Phase averaged centerline η* for B=1.0, Sr=0.15

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Figure 19

Centerline Stanton number ratio, Stf∕Sto, for B=1.0, Sr=0.15

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Figure 20

Phase averaged η* for B=1.0, Sr=0.30; (a) P/NW, (b) P/WO, (c) P/WI

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Figure 4

Time averaged centerline η and η* for B=0.5, Sr=0.15

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Figure 22

Phase averaged centerline η* for B=1.0, Sr=0.30

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Figure 5

Phase averaged centerline η* for B=0.5, Sr=0.15, d=during pulse, b=between pulses

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Figure 6

Centerline Stanton number ratio, Stf∕Sto, for B=0.5, Sr=0.15

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Figure 7

Phase averaged η* for B=0.5, Sr=0.30; (a) P/NW, (b) P/WO, (c) P/WI

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Figure 8

Time averaged centerline η and η* for B=0.5, Sr=0.30

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Figure 9

Phase averaged centerline η* for B=0.5, Sr=0.30

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Figure 10

Centerline Stanton number ratio, Stf∕Sto, for B=0.5, Sr=0.30

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Figure 11

Phase averaged η* for B=0.5, Sr=0.60; (a) P/NW, (b) P/WO, (c) P/WI

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Figure 23

Centerline Stanton number ratio, Stf∕Sto, for B=1.0, Sr=0.30

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Figure 24

Phase averaged η* for B=1.0, Sr=0.60; (a) P/NW, (b) P/WO, (c) P/WI

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Figure 25

Time averaged centerline η and η* for B=1.0, Sr=0.60

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Figure 26

Phase averaged centerline η* for B=1.0, Sr=0.60 cases

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