Film cooling can have a significant effect on the heat transfer coefficient (HTC) between the overflowing freestream gas and the underlying surface. This study investigated the influence of approach flow characteristics, including the boundary layer thickness and character (laminar and turbulent), as well as the approach flow Reynolds number, on the HTC. The figure of merit for this study was the HTC augmentation, that is, the ratio of HTCs for a cooled versus uncooled surface. A heated foil surface provided a known heat flux, allowing direct measurement of HTC and augmentation. The foil was placed both upstream and downstream of the film cooling holes, in order to generate an approaching thermal boundary layer, as representative of actual engine conditions. High-resolution IR thermography provided spatially resolved HTC augmentation data. An open-literature shaped-hole design was used, known as the 7-7-7 hole, in order to compare with existing results in the literature. A variety of blowing conditions were tested from M =0.5 to 3.0. Two elevated density ratios of DR = 1.20 and DR = 1.80 were used. The results indicated that turbulent boundary layer thickness had a modest effect on HTC augmentation, whereas a very high level of augmentation was observed for a laminar approach boundary layer. The presence of upstream heating greatly increased the HTC augmentation in the near-hole region, although these effects died out by 10–15 diameters from the holes.

References

References
1.
Bogard
,
D.
, and
Thole
,
K.
,
2006
, “
Gas Turbine Film Cooling
,”
J. Propul. Power
,
22
(
2
), pp.
249
270
.
2.
Eckert
,
E.
,
1970
, “
Gas-to-Gas Film Cooling
,”
J. Eng. Phys.
,
19
(
3
), pp.
1091
1101
.
3.
Baldauf
,
S.
,
Scheurlen
,
M.
,
Schulz
,
A.
, and
Wittig
,
S.
,
2002
, “
Heat Flux Reduction From Film Cooling and Correlation of Heat Transfer Coefficients From Thermographic Measurements at Enginelike Conditions
,”
ASME J. Turbomach.
,
124
(
4
), pp.
699
709
.
4.
Gritsch
,
M.
,
Schulz
,
A.
, and
Wittig
,
S.
,
2000
, “
Film-Cooling Holes With Expanded Exits: Near-Hole Heat Transfer Coefficients
,”
Int. J. Heat Fluid Flow
,
21
(
2
), pp.
146
155
.
5.
Bonanni
,
L.
,
Bacchini
,
B.
,
Tarchi
,
L.
,
Maritano
,
M.
, and
Traverso
,
S.
,
2010
, “
Heat Transfer Performance of Fan-Shaped Film Cooling Holes—Part I: Experimental Analysis
,”
ASME
Paper No. GT2010-22808.
6.
Boyd
,
E.
,
McClintic
,
J.
,
Chavez
,
K.
, and
Bogard
,
D.
,
2017
, “
Direct Measurement of Heat Transfer Coefficient Augmentation at Multiple Density Ratios
,”
ASME J. Turbomach.
,
139
(
1
), p.
011005
.
7.
Saumweber
,
C.
, and
Schulz
,
A.
,
2012
, “
Free-Stream Effects on the Cooling Performance of Cylindrical and Fan-Shaped Cooling Holes
,”
ASME J. Turbomach.
,
134
(
6
), p.
061007
.
8.
Bunker
,
R.
,
2005
, “
A Review of Shaped Hole Turbine Film Cooling Technology
,”
ASME J. Heat Transfer
,
127
(
4
), pp.
441
453
.
9.
Anderson
,
J.
,
Wilkes
,
E.
,
McClintic
,
J.
, and
Bogard
,
D.
,
2016
, “
Effects of Freestream Mach Number, Reynolds Number and Boundary Layer Thickness on Film Cooling Effectiveness of Shaped Holes
,”
ASME
Paper No. GT2016-56152.
10.
Harrison
,
K.
,
Dorrington
,
J.
,
Dees
,
J.
,
Bogard
,
D.
, and
Bunker
,
R.
,
2009
, “
Turbine Airfoil Net Heat Flux Reduction With Cylindrical Holes Embedded in a Transverse Trench
,”
ASME J. Turbomach.
,
131
(
1
), p.
011012
.
11.
Anderson
,
J.
,
McClintic
,
J.
,
Bogard
,
D.
,
Dyson
,
T.
, and
Webster
,
Z.
,
2017
, “
Freestream Flow Effects on Film Cooling Effectiveness and Heat Transfer Coefficient Augmentation for Compound-Angle Shaped Holes
,”
ASME
Paper No. GT2017-64853.
12.
McClintic
,
J.
,
Klavetter
,
S.
,
Anderson
,
J.
,
Winka
,
J.
,
Bogard
,
D.
,
Dees
,
J.
,
Laskowski
,
G.
, and
Briggs
,
R.
,
2015
, “
The Effect of Internal Cross-Flow on the Adiabatic Effectiveness of Compound Angle Film Cooling Holes
,”
ASME J. Turbomach.
,
137
(
7
), p.
071006
.
13.
Schroeder
,
R.
, and
Thole
,
K.
,
2014
, “
Adiabatic Effectiveness Measurements for a Baseline Shaped Film Cooling Hole
,”
ASME
Paper No. GT2014-25992.
14.
Kays
,
W.
,
Crawford
,
M.
, and
Wiegland
,
B.
,
2003
,
Convective Heat and Mass Transfer
,
McGraw-Hill
,
New York
.
15.
Moffat
,
R.
,
1985
, “
Using Uncertainty Analysis in the Planning of an Experiment
,”
ASME J. Fluids Eng.
,
107
(
2
), pp.
173
178
.
16.
Anderson
,
J.
,
Boyd
,
E.
, and
Bogard
,
D.
,
2015
, “
Experimental Investigation of Coolant-to-Mainstream Scaling Parameters With Cylindrical and Shaped Film Cooling Holes
,”
ASME
Paper No. GT2015-43072.
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