Discrete hole film cooling is widely employed to protect turbine blades and vanes from hot combustion gases entering the high-pressure turbine stage. Accurate prediction of the heat transfer near film cooling holes is critical, and high-fidelity experimental data sets are needed for validation of new computational models. Relatively few studies have examined the effects of periodic main flow unsteadiness resulting from the interaction of turbine blades and vanes, with a particular lack of data for shaped hole configurations. Periodic unsteadiness was generated in the main flow over a laidback, fan-shaped cooling hole at a Strouhal number (St = fD/U) of 0.014 by an airfoil oscillating in pitch. Magnetic resonance imaging (MRI) with water as the working fluid was used to obtain full-field, phase-resolved velocity and scalar concentration data. Operating conditions consisted of a hole Reynolds number of 2900, channel Reynolds number of 25, 000, and blowing ratio of unity. Both mean and phase-resolved data are compared to the previous measurements for the same hole geometry with steady main flow. Under unsteady freestream conditions, the flow separation pattern inside the hole was observed to change from an asymmetric separation bubble to two symmetric bubbles. The periodic unsteadiness was characterized by alternating periods of slow main flow, which allowed the coolant to penetrate into the freestream along the centerplane, and fast, hole-impinging main flow, which deflected coolant toward the laidback wall and caused ejection of coolant from the hole away from the centerplane. Mean adiabatic surface effectiveness was reduced up to 23% inside the hole, while mean laterally averaged effectiveness outside the hole fell 28–36% over the entire measurement domain. A brief comparison to a round jet with and without unsteadiness is included; for the round jet, no disturbance was observed inside the hole, and some fluctuations directed coolant toward the wall, which increased mean film cooling effectiveness. The combined velocity and concentration data for both cases are suitable for quantitative validation of computational fluid dynamics predictions for film cooling flows with periodic freestream unsteadiness.

References

References
1.
Thole
,
K.
,
Sinha
,
A.
,
Bogard
,
D.
, and
Crawford
,
M.
,
1992
, “
Mean Temperature Measurements of Jets With a Crossflow for Gas Turbine Film Cooling Application
,”
Third International Symposium on Transport Phenomena and Dynamics of Rotating Machinery (ISROMAC-3)
, Honolulu, HI, pp.
69
85
.
2.
Womack
,
K. M.
,
Volino
,
R. J.
, and
Schultz
,
M. P.
,
2008
, “
Measurements in Film Cooling Flows With Periodic Wakes
,”
ASME J. Turbomach.
,
130
(
4
), p.
041008
.
3.
Ou
,
S.
, and
Han
,
J.-C.
,
1994
, “
Unsteady Wake Effect on Film Effectiveness and Heat Transfer Coefficient From a Turbine Blade With One Row of Air and CO2 Film Injection
,”
ASME J. Heat Transfer
,
116
(
4
), pp.
921
928
.
4.
Mehendale
,
A. B.
,
Han
,
J.-C.
,
Ou
,
S.
, and
Lee
,
C. P.
,
1994
, “
Unsteady Wake Over a Linear Turbine Blade Cascade With Air and CO2 Film Injection: Part ii Effect on Film Effectiveness and Heat Transfer Distributions
,”
ASME J. Turbomach.
,
116
(
4
), pp.
730
737
.
5.
Du
,
H.
,
Han
,
J.-C.
, and
Ekkad
,
S. V.
,
1998
, “
Effect of Unsteady Wake on Detailed Heat Transfer Coefficient and Film Effectiveness Distributions for a Gas Turbine Blade
,”
ASME J. Turbomach.
,
120
(
4
), pp.
808
817
.
6.
Gomes
,
R. A.
, and
Niehuis
,
R.
,
2011
, “
Film Cooling Effectiveness Measurements With Periodic Unsteady Inflow on Highly Loaded Blades With Main Flow Separation
,”
ASME J. Turbomach.
,
133
(
2
), p.
021019
.
7.
Fan
,
D.
,
Borup
,
D. D.
,
Elkins
,
C. J.
, and
Eaton
,
J. K.
,
2018
, “
Measurements in Discrete Hole Film Cooling Behavior With Periodic Freestream Unsteadiness
,”
Exp. Fluids
,
59
, p. 37.
8.
Ryan
,
K. J.
,
Coletti
,
F.
,
Elkins
,
C. J.
, and
Eaton
,
J. K.
,
2015
, “
Building Block Experiments in Discrete Hole Film Cooling
,”
ASME
Paper No. GT2015-43731.
9.
Bunker
,
R. S.
,
2005
, “
A Review of Shaped Hole Turbine Film-Cooling Technology
,”
ASME J. Heat Transfer
,
127
(
4
), pp.
441
453
.
10.
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
.
11.
Thole
,
K.
,
Gritsch
,
M.
,
Schulz
,
A.
, and
Wittig
,
S.
,
1996
, “
Flowfield Measurements for Film-Cooling Holes With Expanded Exits
,”
ASME J. Turbomach.
,
120
(2), pp. 327–336.
12.
Ryan
,
K. J.
,
Eaton
,
J. K.
,
Elkins
,
C. J.
, and
Iaccarino
,
G.
,
2016
, “
Three-Dimensional Velocity and Concentration Measurements of Turbulent Mixing in Discrete Hole Film Cooling Flows
,” Ph.D. thesis, Stanford University, Stanford, CA.
13.
Ling
,
J.
,
Coletti
,
F.
,
Yapa
,
S. D.
, and
Eaton
,
J. K.
,
2013
, “
Experimentally Informed Optimization of Turbulent Diffusivity for a Discrete Hole Film Cooling Geometry
,”
Int. J. Heat Fluid Flow
,
44
, pp.
348
357
.
14.
Milani
,
P. M.
,
Ling
,
J.
,
Saez-Mischlich
,
G.
,
Bodart
,
J.
, and
Eaton
,
J. K.
,
2017
, “
A Machine Learning Approach for Determining the Turbulent Diffusivity in Film Cooling Flows
,”
ASME
Paper No. GT2017-63299.
15.
Carr
,
L.
,
1988
, “
Progress in Analysis and Prediction of Dynamic Stall
,”
J. Aircraft
,
25
(
1
), pp.
6
17
.
16.
Elkins
,
C. J.
, and
Alley
,
M. T.
,
2007
, “
Magnetic Resonance Velocimetry: Applications of Magnetic Resonance Imaging in the Measurement of Fluid Motion
,”
Exp. Fluids
,
43
(
6
), pp.
823
858
.
17.
Schiavazzi
,
D.
,
Coletti
,
F.
,
Iaccarino
,
G.
, and
Eaton
,
J. K.
,
2014
, “
A Matching Pursuit Approach to Solenoidal Filtering of Three-Dimensional Velocity Measurements
,”
J. Comput. Phys.
,
263
, pp.
206
221
.
18.
Benson
,
M. J.
,
Elkins
,
C. J.
,
Mobley
,
P. D.
,
Alley
,
M. T.
, and
Eaton
,
J. K.
,
2010
, “
Three-Dimensional Concentration Field Measurements in a Mixing Layer Using Magnetic Resonance Imaging
,”
Exp. Fluids
,
49
(
1
), pp.
43
55
.
19.
Yapa
,
S. D.
,
Datri
,
J. L.
,
Schoech
,
J. M.
,
Elkins
,
C. J.
, and
Eaton
,
J. K.
,
2014
, “
Comparison of Magnetic Resonance Concentration Measurements in Water to Temperature Measurements in Compressible Air Flows
,”
Exp. Fluids
,
55
(
11
), p.
1834
.
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