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Research Papers

The Optimal Distribution of Pin Fins for Blade Tip Cap Underside Cooling

[+] Author and Article Information
Gustavo A. Ledezma

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

Ronald S. Bunker

GE Aviation,
West Chester, OH 45069
e-mail: bunker@ge.com

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received June 8, 2014; final manuscript received July 6, 2014; published online xx xx, xxxx. Assoc. Editor: Jim Downs.

J. Turbomach 137(1), 011002 (Sep 04, 2014) (9 pages) Paper No: TURBO-14-1078; doi: 10.1115/1.4028290 History: Received June 08, 2014; Revised July 06, 2014

This article presents a geometric optimization study to maximize the total heat transfer rate between an array of discrete pin fins and the surrounding serpentine cooling flow. The fins are installed on the tip cap underside of a high-pressure turbine blade (HPTB) model. The study has three parts. In the first, the numerical model is validated against experimental data obtained with liquid crystal thermography. In the second part, the heat and fluid flow performance of the pin fin assembly is simulated numerically, using RANS turbulence models in the range 25,000 < Re < 100,000 and Pr ∼ 0.7. The effect of varying the spacing and the tip cap boundary condition is investigated. In the last part of the study, it is shown that the optimal spacing between the pin fins can be correlated following the same theoretical arguments derived in the previous investigations that used simpler geometries.

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References

Liu, Y.-H., Huh, M., Han, J. C., and Chopra, S., 2007, “Heat Transfer in a Two-Pass Rectangular Channel (AR = 1:4) Under High Rotation Numbers,” ASME Paper No. GT2007-27067. [CrossRef]
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Huh, M., Lei, J., Liu, Y.-H., and Han, J. C., 2009, “High Rotation Number Effects on Heat Transfer in a Rectangular (AR = 2:1) Two Pass Channel,” ASME Paper No. GT2009-59421. [CrossRef]
Jenkins, S., von Wolfersdorf, J., Weigand, B., Roediger, T., Knauss, H., and Kraemer, E., 2006, “Time Resolved Heat Transfer Measurements on the Tip Wall of a Ribbed Channel Using a Novel Heat Flux Sensor—Part II: Heat Transfer Results,” ASME Paper No. GT2006-91131. [CrossRef]
Bunker, R. S., 2008, “The Augmentation of Internal Blade Tip-Cap Cooling by Arrays of Shaped Pins,” ASME J. Turbomach., 130(4), p. 041007. [CrossRef]
Xie, G. N., Sundén, B., Wang, L., and Utriainen, E., 2009, “Augmented Heat Transfer of an Internal Blade Tip Wall With Pin-Fins,” ASME Paper No. GT2009-59410. [CrossRef]
Ledezma, G. A., and Bunker, R. S., 2013, “The Optimal Distribution of Chordwise Rib Fin Arrays for Blade Tip Cap Underside Cooling,” ASME J. Turbomach., 136(1), p. 011007. [CrossRef]
Bejan, A., and Morega, A. M., 1994, “The Optimal Spacing of a Stack of Plates Cooled by Turbulent Forced Convection,” Int. J. Heat Mass Transfer, 37(6), pp. 1045–1048. [CrossRef]
Mainardes, R. L. S., Matos, R. S., Vargas, J. V. C., and Ordoñez, J. C., 2007, “Optimally Staggered Finned Circular and Elliptic Tubes in Turbulent Forced Convection,” ASME J. Heat Transfer, 129(5), pp. 674–678. [CrossRef]
Ledezma, G. A., Morega, A. M., and Bejan, A., 1996, “Optimal Spacing Between Pin Fins With Impinging Flow,” ASME J. Heat Transfer, 118(3), pp. 570–577. [CrossRef]
Kline, S. J., and McClintock, F. A., 1953, “Describing Uncertainties in Single-Sample Experiments,” ASME J. Mech. Eng., 75(1), pp. 3–8.
ANSYS, 2010, ansys CFX Release 13, Modeling Guide, ANSYS Inc., Canonsburg, PA.
Ledezma, G. A., Laskowski, G. M., and Tolpadi, A. K., 2008, “Turbulence Model Assessment for Conjugate Heat Transfer in a High Pressure Turbine Vane Model,” ASME Paper No. GT2008-50498. [CrossRef]
Laskowski, G. M., Ledezma,G. A., Tolpadi, A. K., and Ostrowski, M. C., 2008, “CFD Simulations and Conjugate Heat Transfer Analysis of a High Pressure Turbine Vane Utilizing Different Cooling Configurations,” 12th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery (ISROMAC-12), Honolulu, HI, Feb. 17–22, Paper No. ISROMAC12-2008-20065.
Dees, J. E., Bogard, D. G., Ledezma, G. A., Laskowski, G. M., and Tolpadi, A. K., 2010, “Experimental Measurements and Computational Predictions of an Internally Cooled Simulated Turbine Vane With 90 Degree Rib Turbulators,” ASME Paper No. GT2010-23004. [CrossRef]

Figures

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Fig. 1

(a) Assembly view of test model and (b) machined pin fin array

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Fig. 2

Schematic of the simulated 180-deg turn model

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Fig. 3

Example of S = 15.2 mm mesh used in the optimization study: (a) fluid mesh near the 180-deg turn and (b) mesh detail on the surface of the pin fin array

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Fig. 4

Smooth tip cap underside test Nusselt number results, Re = 200,000

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Fig. 5

Smooth tip cap underside CFD, Re = 200,000: (a) Nu contours, (b) velocity-colored Q invariant and Nu contours on the tip cap underside, and (c) 2D streamlines on a constant Y plane parallel to the fins

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Fig. 6

Finned tip cap underside Nu contours, Re = 310,000, S = 12.2 mm: CFD (top) and measurements (bottom)

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Fig. 7

Fin and tip cap underside dimensions

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Fig. 8

Numerical optimization of the pin fin spacing, S˜

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Fig. 9

Effect of the Reynolds number on the optimal fin spacing results

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Fig. 10

Effect of the Reynolds number on the maximum thermal conductance results

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Fig. 11

Smooth and finned tip cap underside CFD results, Re = 100,000, S = 12.2 mm: velocity-colored Q invariant and velocity vectors at a 180-deg turn midplane in X

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Fig. 12

2D streamlines on a constant Y plane parallel to the fins. Re = 100,000 and S = 12.2 mm.

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Fig. 13

Tip cap underside fin array wetted surface temperature for Re = 100,000

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Fig. 14

Effect of tip cap underside fins on the 180-deg turn pressure drop

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