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Research Papers

Experimental-Based Redesigns for Trailing Edge Film Cooling of Gas Turbine Blades

[+] Author and Article Information
Michael Benson

U.S. Military Academy,
West Point, NY 10966 
e-mail: michael.benson@us.army.mil

Sayuri D. Yapa

e-mail: yapasd@stanford.edu

Chris Elkins

e-mail: celkins@stanford.edu

John K. Eaton

e-mail: eatonj@stanford.edu
Stanford University,
Stanford, CA 94305

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 16, 2012; final manuscript received August 7, 2012; published online June 5, 2013. Assoc. Editor: David Wisler.

J. Turbomach 135(4), 041018 (Jun 05, 2013) (9 pages) Paper No: TURBO-12-1147; doi: 10.1115/1.4007601 History: Received July 16, 2012; Revised August 07, 2012

Magnetic resonance imaging experiments have provided the three-dimensional mean concentration and three component mean velocity field for a typical trailing edge film-cooling cutback geometry built into a conventional uncambered airfoil. This geometry is typical of modern aircraft engines and includes three dimensional slot jets separated by tapered lands. Previous analysis of these data identified the critical mean flow structures that contribute to rapid mixing and low effectiveness in the fully turbulent flow. Three new trailing edge geometries were designed to modify the large scale mean flow structures responsible for surface effectiveness degradation. One modification called the Dolphin Nose attempted to weaken strong vortex flows by reducing three dimensionality near the slot breakout. This design changed the flow structure but resulted in minimal improvement in the surface effectiveness. Two other designs called the Shield and Rounded Shield changed the land planform and added an overhanging land edge while maintaining the same breakout surface. These designs substantially modified the vortex structure and improved the surface effectiveness by as much as 30%. Improvements included superior coolant uniformity on the breakout surface which reduces potential thermal stresses. The utilization of the time averaged data from combined magnetic resonance velocimetry (MRV) and concentration (MRC) experiments for designing improved trailing edge breakout film cooling is demonstrated.

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References

Figures

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Fig. 1

Channel test section, with dimensions in mm

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Fig. 2

Top and side views of the airfoil and its internal geometry. External flow is from left to right. Internal flow enters from top and exits through three slots near the trailing edge.

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Fig. 3

Key features of the trailing edge region

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Fig. 4

Isometric views of the (a) Baseline, (b) Dolphin Nose, (c) Shield, and (e) Rounded Shield. A top view (d) of the Shield shows the regions of the lands that are overhung.

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Fig. 5

Isometric views of the (a) Baseline, (b) Dolphin Nose, (c) Shield, and (d) Rounded Shield geometries with reverse flow regions (purple) and streamlines (black)

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Fig. 6

Normalized streamwise vorticity contours in a vertical and spanwise cross plane for the (a) Baseline, (b) Dolphin Nose, (c) Shield, and (d) Rounded Shield at (xxs)/h = 3.0

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Fig. 7

Concentration contours with in-plane velocity vectors for a vertical and spanwise cross plane at (xxs)/h = 5.5. The reference arrows show in-plane velocity magnitude (Ut) normalized by the bulk averaged velocity at the slot exit (Ubulk). (a) Baseline, (b) Dolphin Nose, (c) Shield, and (d) Rounded Shield.

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Fig. 8

Top view of the surface effectiveness contour plots in the center slot for the (a) Baseline, (b) Dolphin Nose, (c) Shield, and (d) Rounded Shield geometries

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Fig. 9

Spanwise averaged surface effectiveness for the baseline case and three redesigns at BR = 1.3. Also included are centerline effectiveness data from Holloway et al. [20] for two blowing ratios.

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Fig. 10

Spanwise averaged surface effectiveness, including land surfaces, for the baseline case and three redesigns at BR = 1.3

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