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Research Papers: Heat Transfer Enhancement

Computational Analysis of Pin-Fin Arrays Effects on Internal Heat Transfer Enhancement of a Blade Tip Wall

[+] Author and Article Information
Gongnan Xie

Department of Energy Sciences, Division of Heat Transfer, Lund University, P.O. Box 118, SE-221 00 Lund, Sweden

Bengt Sundén

Department of Energy Sciences, Division of Heat Transfer, Lund University, P.O. Box 118, SE-221 00 Lund, Swedenbengt.sunden@energy.lth.se

Esa Utriainen, Lieke Wang

 Siemens Industrial Turbomachinery AB, SE-612 83 Finspong, Sweden

J. Heat Transfer 132(3), 031901 (Dec 30, 2009) (11 pages) doi:10.1115/1.4000053 History: Received February 25, 2009; Revised May 29, 2009; Published December 30, 2009; Online December 30, 2009

Cooling methods are strongly needed for the turbine blade tips to ensure a long durability and safe operation. Improving the internal convective cooling is therefore required to increase the blade tip life. A common way to cool the tip is to use serpentine passages with 180-deg turns under the blade tip cap. In this paper, enhanced heat transfer of a blade tip cap has been investigated numerically. The computational models consist of a two-pass channel with a 180-deg turn and various arrays of pin fins mounted on the tip cap, and a smooth two-pass channel. The inlet Reynolds number is ranging from 100,000 to 600,000. The computations are 3D, steady, incompressible, and nonrotating. Details of the 3D fluid flow and heat transfer over the tip walls are presented. The effects of pin-fin height, diameter, and pitches on the heat transfer enhancement on the blade tip walls are observed. The overall performances of ten models are compared and evaluated. It is found that due to the combination of turning, impingement, and pin-fin crossflow, the heat transfer coefficient of the pin-finned tip is a factor of 2.67 higher than that of a smooth tip. This augmentation is achieved at the expense of a penalty of pressure drop around 30%. Results show that the intensity of heat transfer enhancement depends upon pin-fin configuration and arrangement. It is suggested that pin fins could be used to enhance the blade tip heat transfer and cooling.

Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Typical cooling techniques for a turbine blade

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Figure 2

A typical serpentine cooling passage inside a blade

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Figure 3

Schematics of the numerical model

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Figure 4

Typical cross sections of the grids for computations

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Figure 5

Flow fields (upper: smooth tip; lower: pin-finned tip, Case 7)

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Figure 6

Temperature contours (left: Re=200,000; right: Re=440,000)

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Figure 7

Effect of pin-fin height on Nusselt number and pressure drop

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Figure 8

Local Nusselt numbers (Case I, Case II, Case III, Case VII, Re=200,000)

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Figure 9

Effect of pin-fin diameter on Nusselt number and pressure drop

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Figure 10

Effect of pin-fin pitches on Nusselt number and pressure drop

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Figure 11

Local Nusselt numbers of Case 1 and Case 2 at Re=440,000

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Figure 12

Combination effect of pin-fin parameters on Nusselt number and pressure drop

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Figure 13

Normalized Nusselt number and friction factor based on smooth-tip channel

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Figure 14

Comparison of Nusselt number between simulation and experimental data by Bunker (31)

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Figure 15

Performance comparison of various tips under Case 1

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Figure 16

Performance comparison of various tips under Case 2

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