Effects of Surface Deposition, Hole Blockage, and Thermal Barrier Coating Spallation on Vane Endwall Film Cooling

[+] Author and Article Information
N. Sundaram

Mechanical Engineering Department, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061nasundar@vt.edu

K. A. Thole

Department of Mechanical and Nuclear Engineering,  Pennsylvania State University, University Park, PA 16802-1412kthole@psu.edu

J. Turbomach 129(3), 599-607 (Jul 25, 2006) (9 pages) doi:10.1115/1.2720485 History: Received July 17, 2006; Revised July 25, 2006

With the increase in usage of gas turbines for power generation and given that natural gas resources continue to be depleted, it has become increasingly important to search for alternate fuels. One source of alternate fuels is coal derived synthetic fuels. Coal derived fuels, however, contain traces of ash and other contaminants that can deposit on vane and turbine surfaces affecting their heat transfer through reduced film cooling. The endwall of a first stage vane is one such region that can be susceptible to depositions from these contaminants. This study uses a large-scale turbine vane cascade in which the following effects on film cooling adiabatic effectiveness were investigated in the endwall region: the effect of near-hole deposition, the effect of partial film cooling hole blockage, and the effect of spallation of a thermal barrier coating. The results indicated that deposits near the hole exit can sometimes improve the cooling effectiveness at the leading edge, but with increased deposition heights the cooling deteriorates. Partial hole blockage studies revealed that the cooling effectiveness deteriorates with increases in the number of blocked holes. Spallation studies showed that for a spalled endwall surface downstream of the leading edge cooling row, cooling effectiveness worsened with an increase in blowing ratio.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

Illustration of the wind tunnel facility

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Figure 2

Schematic of the surface distortions simulated on the endwall surface

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Figure 3

Illustration of: (a) surface distortions simulated at leading edge; (b) baseline case with upstream slot flow; (c), (d), and (e) lateral average and effectiveness contours of the two baseline cases

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Figure 4

Effectiveness contours comparing the effects of different deposit heights at the leading edge region

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Figure 5

Augmentation of laterally averaged effectiveness due to different deposit heights

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Figure 6

Contours comparing the effects of pressure side deposition: (a) downstream; (b) upstream; and (c) downstream and upstream of holes

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Figure 7

Laterally averaged effectiveness along pressure side (boxed region on the right shows the averaged area)

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Figure 8

Change in adiabatic effectiveness levels along streamlines S1 and S2 (refer to Fig. 3) for deposits on both sides of the cooling rows

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Figure 9

Contours showing the effect of film cooling hole blockage on adiabatic effectiveness

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Figure 10

Laterally averaged effectiveness showing the effect of hole blockages at the leading edge

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Figure 11

Effectiveness contours showing the effect of leading edge spallation at 0.5% and 0.9% film cooling flow rate

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Figure 12

Laterally averaged effectiveness showing the effect of leading edge spallation at different film cooling flow rates

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Figure 13

Contours showing the effect of spallation along midpassage on endwall adiabatic effectiveness

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Figure 14

Comparison of percent reduction on area-averaged adiabatic effectiveness due to surface distortions



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