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Research Papers

Thermal Field Measurements for a Shaped Hole at Low and High Freestream Turbulence Intensity

[+] Author and Article Information
Robert P. Schroeder

Department of Mechanical
and Nuclear Engineering,
The Pennsylvania State University,
University Park, PA 16802
e-mail: rschroeder@sargentlundy.com

Karen A. Thole

Department of Mechanical
and Nuclear Engineering,
The Pennsylvania State University,
University Park, PA 16802
e-mail: kthole@psu.edu

1Present address: Sargent and Lundy, Chicago, IL 60603.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received August 16, 2016; final manuscript received September 1, 2016; published online November 2, 2016. Editor: Kenneth Hall.

J. Turbomach 139(2), 021012 (Nov 02, 2016) (9 pages) Paper No: TURBO-16-1194; doi: 10.1115/1.4034798 History: Received August 16, 2016; Revised September 01, 2016

Shaped holes are increasingly selected for airfoil cooling in gas turbines due to their superior performance over that of cylindrical holes, especially at high blowing ratios. The performance of shaped holes is regarded to be the result of the diffused outlet, which slows and laterally spreads coolant, causing coolant to remain close to the wall. However, few thermal field measurements exist to verify this behavior at high blowing ratio or to evaluate how high freestream turbulence alters the coolant distribution in jets from shaped holes. The present study reports measured thermal fields, along with measured flowfields, for a shaped hole at blowing ratios up to three at both low and high freestream turbulence intensities of 0.5% and 13.2%. Thermal fields at low freestream turbulence intensity showed that the coolant jet was initially attached, but far downstream of the hole the jet lifted away from the surface due to the counter-rotating vortex pair. Elevated freestream turbulence intensity was found to cause strong dilution of the coolant jet and also increased dispersion, almost exclusively in the lateral as opposed to the vertical direction. Dominance of lateral dispersion was due to the influence of the wall on freestream eddies, as indicated from changes in turbulent shear stress between the low and high freestream turbulence cases.

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Copyright © 2017 by ASME
Topics: Turbulence , Coolants
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Figures

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Fig. 1

Schematic of the film cooling wind tunnel

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Fig. 2

Shaped hole geometry

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Fig. 3

Measurement setups for (a) PIV in the centerline plane and (b) stereo PIV in the x/D = 4 crossplane

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Fig. 4

Thermal field profiles showing repeatability for two streamwise locations in the centerline plane. Data are for shaped holes of a separate study at Tu = 0.5%, M = 3.0.

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Fig. 5

Thermal field contours in the z/D = 0 centerline plane at Tu = 0.5% for blowing ratios of (a) M = 1.5 and (b) M = 3.0

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Fig. 6

Thermal field and flowfield profiles at Tu = 0.5% for M = 1.5 and 3 in the centerline plane at (a–d) x/D = 1 and (e–h) x/D = 8

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Fig. 7

Thermal field contours in the z/D = 0 centerline plane for M = 3.0 at Tu = 13.2%. Labeled dashed white lines denote contour levels of θLFST = 0.05, 0.40, and 0.60 for the corresponding case at low freestream turbulence intensity.

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Fig. 8

Thermal field and flowfield profiles at Tu = 13.2% for M = 3 in the centerline plane at (a–d) x/D = 1 and (e–h) x/D = 8. Legend is the same as in Figs. 6(a)6(h).

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Fig. 13

Contours of turbulence intensity in the centerline plane, overlaid with contours levels of θ, at M = 3.0 with freestream turbulence of (a) Tu = 0.5% and (b) Tu = 13.2%

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Fig. 12

Contours of turbulent shear stresses at M = 3.0 in the x/D = 4 crossplane with (a–c) Tu = 0.5% and (d–f) Tu = 13.2%. In-plane mean velocity is shown by gray arrows. The thermal field θ = 0.05 contour level is shown by the black curve.

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Fig. 11

Contours of rms velocity fluctuations at M = 3.0 in the x/D = 4 crossplane with (a–c) Tu = 0.5% and (d–f) Tu = 13.2%. In-plane mean velocity is shown by gray arrows. The thermal field θ = 0.05 contour is shown by the black curve.

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Fig. 10

Comparison of lateral spreading of M = 3.0 jets at freestream turbulence of Tu = 0.5% (dashed lines) and Tu = 13.2% (solid lines) through plotting of η = 0.05 and 0.60 adiabatic effectiveness levels

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Fig. 9

Thermal field contours in the x/D = 10 crossplane at M = 3.0 with freestream turbulence intensities of (a) Tu = 0.5% and (b) Tu = 13.2%

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