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Research Papers

Three-Dimensional Velocity and Scalar Field Measurements of an Airfoil Trailing Edge With Slot Film Cooling: The Effect of an Internal Structure in the Slot

[+] Author and Article Information
Julia Ling

e-mail: julial@stanford.edu

Sayuri D. Yapa

Stanford University,
Stanford, CA 94305

Michael J. Benson

US Military Academy,
West Point, New York 10996

John K. Eaton

Stanford University,
Stanford, CA 94305

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received June 28, 2012; final manuscript received August 6, 2012; published online March 25, 2013. Editor: David Wisler.

J. Turbomach 135(3), 031018 (Mar 25, 2013) (8 pages) Paper No: TURBO-12-1091; doi: 10.1115/1.4007520 History: Received June 28, 2012; Revised August 06, 2012

Measurements of the 3D velocity and concentration fields were obtained using magnetic resonance imaging for a pressure-side cutback film cooling experiment. The cutback geometry consisted of rectangular slots separated by straight lands; inside each of the slots was an airfoil-shaped blockage. The results from this trailing edge configuration, the “island airfoil,” are compared to the results obtained with the “generic airfoil,” a geometry with narrower slots, wider, tapered lands, and no blockages. The objective was to determine how the narrower lands and internal blockages affected the average film cooling effectiveness and the spanwise uniformity. Velocimetry data revealed that strong horseshoe vortices formed around the blockages in the slots, which resulted in greater coolant nonuniformity on the airfoil breakout surface and in the wake. The thinner lands of the island airfoil allowed the coolant to cover a larger fraction of the trailing edge span, giving a much higher spanwise-averaged surface effectiveness, especially near the slot exit where the generic airfoil lands are widest.

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References

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Figures

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Fig. 1

Schematic of the experimental apparatus

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Fig. 2

Schematics of the airfoil

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Fig. 3

Contours of streamwise velocity, nondimensionalized by bulk velocity, 2 mm above the breakout surface. A cutaway model of the airfoil is superimposed in black, with a dashed white line shown at the plane of the slot exit. Regions of separated flow are shown in blue.

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Fig. 4

Contours of streamwise vorticity. Vorticity nondimensionalized by bulk velocity and slot height. Regions of solid airfoil shown in black.

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Fig. 5

Contours of coolant concentration on the island airfoil, looking into the center slot. In-plane velocity vectors overlaid in black. Model of airfoil superimposed in gray. Fig. 5(b) shows the region within the white box in 5(a).

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Fig. 6

Isosurfaces of coolant concentration, colored by isosurface height above the breakout surface nondimensionalized by slot height. Model of airfoil superimposed in black.

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Fig. 7

Contours of surface effectiveness on the breakout surface. Outline of lands shown in gray.

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Fig. 8

Spanwise averaged surface effectiveness on the breakout surface of the generic (red) and island airfoils (black) for averages including (solid —–) and excluding (dashed - - -) the lands.

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