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Research Papers

Film-Cooled Trailing Edge Measurements: 3D Velocity and Scalar Field

[+] Author and Article Information
Michael Benson

U.S. Military Academy
West Point, NY 10996
e-mail: michael.benson@usma.edu

Gregory Laskowski

GE Global Research Center
Niskayuna, NY 12309
e-mail: laskowsk@ge.com

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 August 4, 2011; final manuscript received August 10, 2011; published online October 30, 2012. Editor: David Wisler.

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. Approved for public release, distribution is unlimited.

J. Turbomach 135(1), 011030 (Oct 30, 2012) (7 pages) Paper No: TURBO-11-1176; doi: 10.1115/1.4006425 History: Received August 04, 2011; Revised August 10, 2011

Aircraft turbine blade trailing edges commonly are cooled by blowing air through pressure-side cutback slots. The surface effectiveness is governed by the rate of mixing of the coolant with the mainstream, which is typically much faster than predicted by CFD models. Three-dimensional velocity and coolant concentration fields were measured in and around a cutback slot using a simple uncambered airfoil with a realistic trailing edge cooling geometry at a Reynolds number of 110,000 based on airfoil chord length, which is lower than practical engines but still in the turbulent regime. The results were obtained using magnetic resonance imaging (MRI) techniques in a water flow apparatus. Magnetic resonance concentration (MRC) scans measured the concentration distribution with a spatial resolution of 0.5 mm3 (compared to a slot height of 5 mm) and an uncertainty near 5%. Magnetic resonance velocimetry (MRV) was used to acquire 3D, three-component mean velocity measurements with a resolution of 1.0 mm3. Coupled concentration and velocity measurements were used to identify flow structures contributing to the rapid mixing, including longitudinal vortices and separation bubbles. Velocity measurements at several locations were compared with an unsteady RANS model. Concentration measurements extrapolated to the surface provided film cooling effectiveness and showed that the longitudinal vortices decreased effectiveness near the lands and reduced the average film cooling effectiveness.

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References

Holloway, D. S., Leylek, J. H., and Buck, F. A., 2002, “Pressure-Side Bleed Film Cooling: Part II—Unsteady Framework for Experimental and Computational Results,” ASME Paper No. GT2002-30472. [CrossRef]
Martini, P., Schulz, A., Bauer, H., and Whitney, C., 2006, “Detached Eddy Simulation of Film Cooling Performance on the Trailing Edge Cutback of Gas Turbine Airfoils,” ASME J. Turbomach., 128, pp. 292–299. [CrossRef]
Joo, J., and Durbin, P., 2009, “Simulation of Turbine Blade Trailing Edge Cooling,” ASME J. Fluids Eng., 131, pp. 1–14. [CrossRef]
Taslim, M., Spring, S., and Mehlman, B., 1992, “Experimental Investigation of Film Cooling Effectiveness for Slots of Various Exit Geometries,” J. Thermophys. Heat Transfer, 6(2), pp. 302–307. [CrossRef]
Holloway, D. S., Leylek, J. H., and Buck, F. A., 2002, “Pressure-Side Bleed Film Cooling: Part I—Steady Framework for Experimental and Computational Results,” ASME Paper No. GT2002-30471. [CrossRef]
Martini, P., Schulz, A., and Bauer, H., 2006, “Film Cooling Effectiveness and Heat Transfer on the Trailing Edge Cutback of Gas Turbine Airfoils With Various Internal Cooling Designs,” ASME J. Turbomach.128, pp. 196–205. [CrossRef]
Cunha, F., and Chyu, M., 2006, “Trailing-Edge Cooling for Gas Turbines,” J. Propul. Power, 22(2), pp. 286–300. [CrossRef]
Choi, J., Mhetras, S., Lau, S., and Rudolph, R., 2008, “Film Cooling and Heat Transfer on Two Cutback Trailing Edge Models With Internal Perforated Blockages,” ASME J. Heat Transfer, 130, pp. 1–13. [CrossRef]
Dannhauer, A., 2009, “Investigation of Trailing Edge Cooling Concepts in a High Pressure Turbine Cascade: Analysis of the Adiabatic Film Cooling Effectiveness,” ASME Paper No. GT2009-59343. [CrossRef]
Krueckels, J., Gritsch, M., and Schnieder, M., 2009, “Design Considerations and Validation of Trailing Edge Pressure Side Bleed Cooling,” ASME Paper No. GT2009-59161. [CrossRef]
Fiala, N., Jaswal, I., and Ames, F., 2010, “Letterbox Trailing Edge Heat Transfer: Effects of Blowing Rate, Reynolds Number, and External Turbulence on Heat Transfer and Film Cooling Effectiveness,” ASME J. Turbomach., 132, pp. 1–10. [CrossRef]
Elkins, C., and Alley, M., 2007, “Magnetic Resonance Velocimetry: Applications of Magnetic Resonance Imaging in the Measurement of Fluid Motion,” Exp. Fluids, 43, pp. 823–858. [CrossRef]
Benson, M., 2011, “Measurements of 3D Velocity and Scalar Field for a Film-Cooled Airfoil Trailing Edge,” dissertation, Stanford University, Stanford, CA.
Benson, M., Elkins, C., Mobley, P., Alley, M., and Eaton, J., 2010, “Three Dimensional Concentration Field Measurements in a Mixing Layer Using Magnetic Resonance Imaging,” Exp. Fluids, 49(1), pp. 43–55. [CrossRef]
Elkins, C. J., Markl, M., Pelc, N., and Eaton, J., 2003, “4D Magnetic Resonance Velocimetry for Mean Velocity Measurements in Complex Turbulent Flows,” Exp. Fluids, 34(4), pp. 494–503. [CrossRef]
Baldauf, S., and Scheurlen, M., 2002, “Correlation of Film-Cooling Effectiveness From Thermographic Measurements at Enginelike Conditions,” ASME J. Turbomach., 124, pp. 686–698. [CrossRef]
Chen, Y., Matalanis, C., and Eaton, J., 2008, “High Resolution PIV Measurements Around a Model Turbine Blade Trailing Edge Film-Cooling Breakout,” Exp. Fluids, 44, pp. 199–209. [CrossRef]
Laskowski, G., and Felten, F., 2010, “Steady and Unsteady CFD Simulations of Transonic Turbine Vane Wakes With Trailing Edge Cooling,” European Conference on Computational Fluid Dynamics, Lisbon, Portugal, June 14–17.
Burns, W., and Stollery, J., 1968, “The Influence of Foreign Gas Injection and Slot Geometry on Film Cooling Effectiveness,” Int. J. Heat Mass Transfer, 12, pp. 935–951. [CrossRef]
Bittlinger, G., Schulz, A., and Wittig, S., 1994, “Film Cooling Effectiveness and Heat Transfer Coefficients for Slot Injection at High Blowing Ratios,” ASME Paper No. GT1994-182.

Figures

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Fig. 1

Cross-sectional top view of flow apparatus, with flow from left to right. Dimensions in millimeters.

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Fig. 2

Side and top view of airfoil. Flow is left to right, with the y coordinate axis highlighted.

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Fig. 3

Key features of the trailing edge region

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Fig. 4

CFD mesh for airfoil and channel simulation

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Fig. 5

Velocity profiles for CFD (dashed) and MRV (solid) at 3 streamwise locations

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Fig. 6

Iso-surfaces of fast (red) and reverse (purple) flow for the trailing edge. U 1.3*Umain are shown in red. Streamlines in black depict freestream flow from positions centered above the slot and land.

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Fig. 7

Concentration flux at each streamwise position

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Fig. 8

The 10% concentration iso-surface

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Fig. 9

Surface effectiveness for the three slots; 90% effectiveness contour highlighted

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Fig. 10

Spanwise averaged surface effectiveness variation downstream of slot exit

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Fig. 11

Wake dispersion from the middle of the center slot jet. Lines added to highlight airfoil exterior edges.

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Fig. 12

Measured coolant field 4 slot heights downstream of the trailing edge

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Fig. 13

Experimental concentration contours and velocity vectors for a slot centerplane. Lines added to emphasize airfoil surfaces.

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Fig. 14

Multiple planes of concentration contours with tangential velocity vectors

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Fig. 15

Coolant distribution at 8 slot heights downstream of slot exit

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