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TECHNICAL PAPERS

Effect of Unheated Starting Lengths on Film Cooling Experiments

[+] Author and Article Information
Sarah M. Coulthard, Karen A. Flack

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

Ralph J. Volino

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

J. Turbomach 128(3), 579-588 (Jan 16, 2006) (10 pages) doi:10.1115/1.2184355 History: Received December 19, 2005; Revised January 16, 2006

The effect of an unheated starting length upstream of a row of film cooling holes was studied experimentally to determine its effect on heat transfer coefficients downstream of the holes. Cases with a single row of cylindrical film cooling holes inclined at 35deg to the surface of a flat plate were considered at blowing ratios of 0.25, 0.5, 1.0, and 1.5. For each case, experiments were conducted to determine the film-cooling effectiveness and the Stanton number distributions in cases with the surface upstream of the holes heated and unheated. Measurements were made using an infrared camera, thermocouples, and hot and cold-wire anemometry. Ratios were computed of the Stanton number with film cooling (Stf) to corresponding Stanton numbers in cases without film cooling (Sto), but the same surface heating conditions. Contours of these ratios were qualitatively the same regardless of the upstream heating conditions, but the ratios were larger for the cases with a heating starting length. Differences were most pronounced just downstream of the holes and for the lower blowing rate cases. Even 12 diameters downstream of the holes, the Stanton number ratios were 10–15% higher with a heated starting length. At higher blowing rates the differences between the heated and unheated starting length cases were not significant. The differences in Stanton number distributions are related to jet flow structures, which vary with blowing rate.

Copyright © 2006 by American Society of Mechanical Engineers
Topics: Cooling , Jets
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References

Figures

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Figure 1

Wind tunnel configuration

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Figure 2

Test wall with side walls

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Figure 3

Heater configuration

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Figure 4

Dimensionless temperature profile, θ, at exit plane of center hole with B=0.5

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Figure 5

Dimensionless velocity profile, Ujet∕U∞, at exit plane of center hole with B=0.5

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Figure 6

Sto for various heater configurations

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Figure 7

Film cooling effectiveness contour plot for B=0.25

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Figure 8

Film cooling effectiveness contour plot for B=0.5

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Figure 9

Film cooling effectiveness contour plot for B=1.0

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Figure 10

Centerline, z∕D=0, film cooling effectiveness

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Figure 11

Spanwise-averaged film cooling effectiveness

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Figure 12

Stf∕Sto for B=0.25 with unheated starting length

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Figure 13

Stf∕Sto for B=0.25 with heated starting length

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Figure 14

Stf∕Sto for B=0.5 with unheated starting length

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Figure 15

Stf∕Sto for B=0.5 with heated starting length

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Figure 16

Stf∕Sto for B=1.0 with unheated starting length

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Figure 17

Stf∕Sto for B=1.0 with heated starting length

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Figure 18

Stf∕Sto for B=1.5 with unheated starting length

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Figure 19

Stf∕Sto for B=1.5 with heated starting length

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Figure 20

Stf∕Sto for B=0.25 at x∕D=1

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Figure 21

Stf∕Sto for B=0.25 at x∕D=6

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Figure 22

Stf∕Sto for B=0.25 at x∕D=12

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Figure 23

Stf∕Sto for B=0.5 at x∕D=1

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Figure 24

Stf∕Sto for B=0.5 at x∕D=6

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Figure 25

Stf∕Sto for B=0.5 at x∕D=12

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Figure 26

Stf∕Sto for B=1.0 at x∕D=1

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Figure 27

Stf∕Sto for B=1.0 at x∕D=6

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Figure 28

Stf∕Sto for B=1.0 at x∕D=12

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Figure 29

Stf∕Sto for B=1.5 at x∕D=1 (note scale change for this figure)

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Figure 30

Stf∕Sto for B=1.5 at x∕D=6

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Figure 31

Stf∕Sto for B=1.5 at x∕D=12

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Figure 32

Temperature, θ, for B=0.5 at x∕D=3.5

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Figure 33

Temperature, θ, for B=0.5 at x∕D=7

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Figure 34

Temperature, θ, for B=0.5 at x∕D=14

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Figure 35

Temperature, θ, for B=1.0 at x∕D=3.5

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Figure 36

Temperature, θ, for B=1.0 at x∕D=7

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Figure 37

Temperature, θ, for B=1.0 at x∕D=14

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