Effect of Midpassage Gap, Endwall Misalignment, and Roughness on Endwall Film-Cooling

[+] Author and Article Information
N. D. Cardwell, N. Sundaram, K. A. Thole

Mechanical Engineering Department, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061

J. Turbomach 128(1), 62-70 (Feb 01, 2005) (9 pages) doi:10.1115/1.2098791 History: Received October 01, 2004; Revised February 01, 2005

To maintain acceptable turbine airfoil temperatures, film cooling is typically used whereby coolant, extracted from the compressor, is injected through component surfaces. In manufacturing a turbine, the first stage vanes are cast in either single airfoils or double airfoils. As the engine is assembled, these singlets or doublets are placed in a turbine disk in which there are inherent gaps between the airfoils. The turbine is designed to allow outflow of high-pressure coolant rather than hot gas ingestion. Moreover, it is quite possible that the singlets or doublets become misaligned during engine operation. It has also become of interest to the turbine community as to the effect of corrosion and deposition of particles on component heat transfer. This study uses a large-scale turbine vane in which the following two effects are investigated: the effect of a midpassage gap on endwall film cooling and the effect of roughness on endwall film cooling. The results indicate that the midpassage gap was found to have a significant effect on the coolant exiting from the combustor-turbine interface slot. When the gap is misaligned, the results indicate a severe reduction in the film-cooling effectiveness in the case where the pressure side endwall is below the endwall associated with the suction side of the adjacent vane.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Directions of the coolant hole injection along with isovelocity contours and the midpassage gap location for mating two turbine vane platforms

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Figure 2

Cross-section view (section AA, Fig. 1) of the midpassage gap plenum and accompanying seal strip (see Table 2)

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Figure 3

Side and upstream views of the three alignment modes for two adjacent vane platforms

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Figure 4

Illustration of the wind tunnel facility

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Figure 5

Separate plenums for film cooling and upstream slot provided independent control of the flow through each of them

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Figure 6

Contours of adiabatic effectiveness for film-cooling cases (a) rough endwall with midpassage slot and (b) smooth endwall with no midpassage slot

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Figure 7

Plots of laterally averaged adiabatic effectiveness on the film-cooling holes on the pressure side: (a) for 0.75% upstream slot flow and 0.5% film cooling and (b) 0.75% upstream slot flow and 0.75% film cooling

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Figure 8

Laterally averaged adiabatic effectiveness for 0.35%, 0. 5%, and 0.75% film-cooling flows for a rough endwall

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Figure 9

Contours of adiabatic effectiveness with a rough endwall with 0.75% slot flow for (a) 0.35% film cooling; (b) 0.5% film cooling; (c) 0.75% film cooling

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Figure 10

Contours of adiabatic effectiveness on a rough endwall for the baseline film and slot cooling cases: (a) aligned, (b) dam, and (c) cascade endwall (note that U refers to raised side and D refers to lowered side)

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Figure 11

Pitchwise-averaged adiabatic effectiveness for the baseline film and slot cooling cases: (a) along the suction side for the three endwall settings; (b) comparison between effectiveness on the suction and pressure side

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Figure 12

Nondimensionalized gap temperature profiles for the three endwall alignment modes and the velocity profile for an aligned gap

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Figure 13

Contours of adiabatic effectiveness on a rough endwall with cascade setting for different upstream slot flow rate with 0.5% film cooling: (a) 0.75% (I=0.08) slot flow; (b) 0.95% (I=0.12) slot flow; (c) 1.1% (I=0.16) slot flow



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