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Research Papers

Heat Transfer Measurements in a Leading Edge Geometry With Racetrack Holes and Film Cooling Extraction

[+] Author and Article Information
Francesco Maiuolo

e-mail: francesco.maiuolo@htc.de.unifi.it

Lorenzo Tarchi

“S. Stecco” Energy Engineering Department,
University of Florence,
Via S. Marta, 3, 50139 Florence, Italy

Stefano Zecchi

Engineering, Research & Development,
AVIO S.p.A., Via Primo Maggio 56,
Rivalta di Torino,
Turin 10040, Italy
e-mail: stefano.zecchi@aviogroup.com

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Turbomachinery. Manuscript received June 29, 2012; final manuscript received August 6, 2012; published online March 25, 2013. Editor: David Wisler.

J. Turbomach 135(3), 031020 (Mar 25, 2013) (9 pages) Paper No: TURBO-12-1097; doi: 10.1115/1.4007527 History: Received June 29, 2012; Revised August 06, 2012

An experimental survey on a state of the art leading edge cooling scheme was performed to evaluate heat transfer coefficients (HTC) on a large scale test facility simulating a high pressure turbine airfoil leading edge cavity. The test section includes a trapezoidal supply channel with three large racetrack impingement holes. On the internal surface of the leading edge, four big fins are placed in order to confine impingement jets. The coolant flow impacts the leading edge internal surface, and it is extracted from the leading edge cavity through 24 showerhead holes and 24 film cooling holes. The aim of the present study is to investigate the combined effects of jet impingement and mass flow extraction on the internal heat transfer of the leading edge. A nonuniform mass flow extraction was also imposed to reproduce the effects of the pressure side and suction side external pressure. Measurements were performed by means of a transient technique using narrow band thermochromic liquid crystals (TLCs). Jet Reynolds number and crossflow conditions into the supply channel were varied in order to cover the typical engine conditions of these cooling systems (Rej=10,000-40,000). Experiments were compared with a numerical analysis on the same test case in order to better understand flow interaction inside the cavity. Results are reported in terms of detailed 2D maps, radial-wise, and span-wise averaged values of Nusselt number.

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References

Figures

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Fig. 3

Crossflow conditions scheme

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Fig. 2

SH and FC mass flow extraction

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Fig. 9

Central module, %Cr=40: coolant jet impinging zones

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Fig. 5

Nu/Nuavg maps at Rej = 10,000 – 20,000 – 30,000

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Fig. 4

CFD setup: (up) numerical domain; (down) numerical grid

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Fig. 6

Nusselt number averaged values

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Fig. 7

Comparison with published data

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Fig. 8

Central module, %Cr=40: velocity streamlines

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