Modern gas-turbine engines are characterized by high core-flow temperatures and significantly lower turbine-surface temperatures. This can lead to large property variations within the boundary layers on the turbine surfaces. However, cooling of turbines is generally studied near room temperature, where property variation within the boundary layer is negligible. The present study first employs computational fluid dynamics to validate two methods for quantifying the effect of variable properties in a boundary layer: the reference temperature method and the temperature ratio method. The computational results are then used to expand the generality of the temperature ratio method by proposing a slight modification. Next, these methods are used to quantify the effect of variable properties within a boundary layer on measurement techniques, which assume constant properties. Both low-temperature flows near ambient and high-temperature flows with a freestream temperature of $1600 K$ are considered under both laminar and turbulent conditions. The results show that variable properties have little effect on laminar flows at any temperature or turbulent flows at low temperatures such that constant property methods can be validly employed. However, variable properties are seen to have a profound effect on turbulent flows at high temperatures. For the high-temperature turbulent flow considered, the constant property methods are found to overpredict the convective heat transfer coefficient by up to $54.7%$ and underpredict the adiabatic wall temperature by up to $209 K$. Utilizing the variable property techniques, a new method for measuring the adiabatic wall temperature and variable property heat-transfer coefficient is proposed for variable property flows.

## References

References
1.
Bogard
,
D. G.
, and
Thole
,
K. A.
,
2006
, “
Gas Turbine Film Cooling
,”
J. Propul. Power
,
22
(
2
), pp.
249
270
.10.2514/1.18034
2.
Popp
,
O.
,
Smith
,
D. E.
,
Bubb
,
J. V.
,
Grabowski
,
H. C. I.
,
Diller
,
T.
,
Schetz
,
J. A.
, and
Ng
,
W.-F.
,
1999
, “
Steady and Unsteady Heat Transfer in a Transonic Film Cooled Turbine Cascade
,” ASME Paper No. 99-GT-259.
3.
Vedula
,
R. J.
, and
Metzger
,
D. E.
,
1991
, “
A Method for the Simultaneous Determination of Local Effectiveness and Heat Transfer Distributions in Three-Temperature Convection Situations
,”
36th ASME International Gas Turbine and Aeroengine Congress and Exposition, Orlando, FL, June 3–6
.
4.
Myers
,
G. E.
,
1998
,
Analytical Methods in Conduction Heat Transfer
, AMCHT, Madison, WI.
5.
Ekkad
,
S. V.
,
Ou
,
S.
, and
Rivir
,
R. B.
,
2004
, “
A Transient Infrared Thermography Method for Simultaneous Film Cooling Effectiveness and Heat Transfer Coefficient Measurements From a Single Test
,”
ASME J. Turbomach.
,
126
(
4
), pp.
597
603
.10.1115/1.1791283
6.
Lukachko
,
S. P.
,
Kirk
,
D. R.
, and
Waitz
,
I. A.
,
2002
, “
Turbine Durability Impacts of High Fuel-Air Ratio Combustors: Part I—Potential for Intra-Turbine Oxidation of Partially Reacted Fuel
,”
ASME
Paper No. GT2002-30077. 10.1115/GT2002-30077
7.
Polanka
,
M. D.
,
Zelina
,
J.
,
Anderson
,
W. S.
,
Sekar
,
B.
,
Evans
,
D. S.
,
Lin
,
C.-X.
, and
Stouffer
,
S. D.
,
2011
, “
Heat Release in Turbine Cooling I: Experimental and Computational Comparison of Three Geometries
,”
J. Propul. Power
,
27
(
2
), pp.
257
268
.10.2514/1.45317
8.
DeLallo
,
M. R.
,
2012
, “
Impact of Trench and Ramp Film Cooling Designs to Reduce Heat Release Effects in a Reacting Flow
,” M.S. thesis, Air Force Institute of Technology, Wright-Patterson AFB, OH.
9.
White
,
F. M.
,
2006
,
Viscous Fluid Flow
(McGraw-Hill Series in Mechanical Engineering), McGraw-Hill
,
New York
.
10.
Kays
,
W. M.
,
Crawford
,
M. E.
, and
Weigand
,
B.
,
2005
,
Convective Heat and Mass Transfer
(McGraw-Hill Series in Mechanical Engineering), McGraw-Hill
,
New York
.
11.
Eckert
,
E. R. G.
,
1955
, “
Engineering Relations for Friction and Heat Transfer to Surfaces in High Velocity Flow
,”
J. Aeronaut. Sci.
,
22
(
8
), pp.
585
587
.
12.
Blazek
,
J.
,
2005
,
Computational Fluid Dynamics: Principles and Applications
,
Elsevier
,
New York
.
13.
Rumsey
,
C. L.
, and
Spalart
,
P. R.
,
2009
, “
Turbulence Model Behavior in Low Reynolds Number Regions of Aerodynamic Flowfields
,”
AIAA J.
,
47
(
4
), pp.
982
993
.10.2514/1.39947
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