Film Cooling Effectiveness and Heat Transfer on the Trailing Edge Cutback of Gas Turbine Airfoils With Various Internal Cooling Designs

[+] Author and Article Information
P. Martini, A. Schulz, H.-J. Bauer

Lehrstuhl und Institut für Thermische Strömungsmaschinen,  Universität Karlsruhe (TH), Kaiserstr. 12, 76128 Karlsruhe, Germany

J. Turbomach 128(1), 196-205 (Feb 01, 2005) (10 pages) doi:10.1115/1.2103094 History: Received October 01, 2004; Revised February 01, 2005

The present study deals with trailing edge film cooling on the pressure side cutback of gas turbine airfoils. Before being ejected tangentially onto the inclined cut-back surface the coolant air passes a partly converging passage that is equipped with turbulators such as pin fins and ribs. The experiments are conducted in a generic setup and cover a broad variety of internal cooling designs. A subsonic atmospheric open-loop wind tunnel is utilized for the tests. The test conditions are characterized by a constant Reynolds number of Rehg=250000, a turbulence intensity of Tuhg=7%, and a hot gas temperature of Thg=500K. Due to the ambient temperature of the coolant, engine realistic density ratios between coolant and hot gas can be realized. Blowing ratios cover a range of 0.20<M<1.25. The experimental data to be presented include discharge coefficients, adiabatic film cooling effectiveness, and heat transfer coefficients in the near slot region (xH<15). The results clearly demonstrate the strong influence of the internal cooling design and the relatively thick pressure side lip (tH=1) on film cooling performance downstream of the ejection slot.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Cross-sectional view of a turbine blade with pressure side cutback

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Figure 2

Schematic view of the atmospheric test facility

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Figure 3

Cross-sectional view of the trailing edge model and internal cooling design (key dimensions see Table 1)

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Figure 4

Discharge coefficient of the trailing edge slots

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Figure 5

Discharge coefficients CD* of the trailing edge slots based on Athroat

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Figure 6

Local distribution of adiabatic film cooling effectiveness downstream of the slot

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Figure 7

Laterally averaged adiabatic film cooling effectiveness

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Figure 8

Variation of the effective core region with the blowing ratio

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Figure 9

Decay of adiabatic film cooling effectiveness downstream of the effective core region (x0.90)

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Figure 10

Laterally averaged heat transfer coefficients downstream of the slot exit and heat transfer for the turbulent boundary layer on a flat plate

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Figure 11

Local distribution of heat transfer coefficients downstream of the slot

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Figure 12

Laterally averaged heat transfer coefficients

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Figure 13

Variation of Stc with Rec,x for different trailing edge slots at x∕H=4 and for the flat plate

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Figure 14

Prediction of the instantaneous velocity and temperature field on the cut-back (G1,s∕H=6,M=0.50) in a plane between two ribs (z∕H=3)




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