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Research Papers

The Effect of Rib Turbulators on Film Cooling Effectiveness of Round Compound Angle Holes Fed by an Internal Cross-Flow

[+] Author and Article Information
Sean R. Klavetter

Department of Mechanical Engineering,
The University of Texas at Austin,
204 E. Dean Keeton Street,
Austin, TX 78712
e-mail: seanyklav@gmail.com

John W. McClintic

Department of Mechanical Engineering,
The University of Texas at Austin,
204 E. Dean Keeton Street,
Austin, TX 78712
e-mail: jmcclintic@utexas.edu

David G. Bogard

Department of Mechanical Engineering,
The University of Texas at Austin,
204 E. Dean Keeton Street,
Austin, TX 78712
e-mail: dbogard@mail.utexas.edu

Jason E. Dees

GE Global Research Center,
1 Research Circle,
Schenectady, NY 12309
e-mail: deesj@ge.com

Gregory M. Laskowski

GE Aviation,
1000 Western Avenue,
Lynn, MA 01905
e-mail: laskowsk@ge.com

Robert Briggs

GE Aviation,
1 Neumann Way,
Cincinnati, OH 45215
e-mail: robert1.briggs@ge.com

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received February 22, 2016; final manuscript received February 25, 2016; published online June 14, 2016. Editor: Kenneth C. Hall.

J. Turbomach 138(12), 121006 (Jun 14, 2016) (10 pages) Paper No: TURBO-16-1047; doi: 10.1115/1.4032928 History: Received February 22, 2016; Revised February 25, 2016

Early stage gas turbine blades feature complicated internal geometries in order to enhance internal heat transfer and to supply coolant for film cooling. Most film cooling experiments decouple the effect of internal coolant feed from external film cooling effectiveness, even though engine parts are commonly fed by cross-flow and feature internal rib turbulators which can affect film cooling. Experiments measuring adiabatic effectiveness were conducted to investigate the effects of turbulated perpendicular cross-flow on a row of 45 deg compound angle cylindrical film cooling holes for a total of eight internal rib configurations. The ribs were angled to the direction of prevailing internal cross-flow at two different angles: 45 deg or 135 deg. The ribs were also positioned at two different spanwise locations relative to the cooling holes: in the middle of the cooling hole pitch and slightly intersecting the holes. Experiments were conducted at a density ratio of DR = 1.5 for a range of blowing ratios including M = 0.5, 0.75, 1.0, 1.5, and 2.0. This study demonstrates that peak effectiveness can be attained through the optimization of cross-flow direction relative to the compound angle direction and rib configuration, verifying the importance of hole inlet conditions in film cooling experiments. It was found that ribs tend to reduce adiabatic effectiveness relative to a baseline, smooth-walled configuration. Rib configurations that directed the internal coolant forward in the direction of the mainstream resulted in higher peak adiabatic effectiveness. However, no other parameters could consistently be identified correlating to increased film cooling performance. It is likely that a combination of factors is responsible for influencing performance, including internal local pressure caused by the ribs, the internal channel flow field, in-hole vortices, and jet exit velocity profiles. This study also attempted to replicate the possibility that film cooling holes may intersect ribs and found that a hole which partially intersects a rib still maintains moderate levels of effectiveness.

Copyright © 2016 by ASME
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References

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Figures

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Fig. 1

Schematic of wind tunnel test section

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Fig. 2

Schematic of closed-loop wind tunnel test facility

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Fig. 3

Schematic of rib configurations tested in this study as seen from inside the channel

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Fig. 4

Nomenclature for holes relative to rib location

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Fig. 5

Sample IR camera calibration

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Fig. 6

Spatially averaged effectiveness curves for all the rib configurations tested compared to baseline smooth wall results from Ref. [22]. The notation (F) or (B) represents a forward or backward deflecting rib configuration.

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Fig. 7

Laterally averaged effectiveness data for the perpendicular midpitch configuration

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Fig. 8

Laterally averaged effectiveness data for the aligned midpitch configuration

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Fig. 9

Effectiveness contours for the perpendicular midpitch configuration

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Fig. 10

Spatially averaged effectiveness for the perpendicular midpitch configuration

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Fig. 11

Spatially averaged effectiveness for the aligned midpitch configuration

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Fig. 12

Laterally averaged adiabatic effectiveness for the perpendicular over-holes configuration

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Fig. 13

Laterally averaged adiabatic effectiveness for the aligned over-holes configuration

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Fig. 14

Spatially averaged effectiveness for the perpendicular over-holes configuration

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Fig. 15

Spatially averaged effectiveness for the aligned over-holes configuration

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Fig. 16

Contour comparisons of optimum blowing ratios for (1) smooth-walled, (2) aligned midpitch, (3) aligned over-hole, (4) perpendicular midpitch, and (5) perpendicular over-hole configurations

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