Aircraft turbine blade trailing edges commonly are cooled by blowing air through pressure-side cutback slots. The surface effectiveness is governed by the rate of mixing of the coolant with the mainstream, which is typically much faster than predicted by CFD models. Three-dimensional velocity and coolant concentration fields were measured in and around a cutback slot using a simple uncambered airfoil with a realistic trailing edge cooling geometry at a Reynolds number of 110,000 based on airfoil chord length, which is lower than practical engines but still in the turbulent regime. The results were obtained using magnetic resonance imaging (MRI) techniques in a water flow apparatus. Magnetic resonance concentration (MRC) scans measured the concentration distribution with a spatial resolution of 0.5 mm3 (compared to a slot height of 5 mm) and an uncertainty near 5%. Magnetic resonance velocimetry (MRV) was used to acquire 3D, three-component mean velocity measurements with a resolution of 1.0 mm3. Coupled concentration and velocity measurements were used to identify flow structures contributing to the rapid mixing, including longitudinal vortices and separation bubbles. Velocity measurements at several locations were compared with an unsteady RANS model. Concentration measurements extrapolated to the surface provided film cooling effectiveness and showed that the longitudinal vortices decreased effectiveness near the lands and reduced the average film cooling effectiveness.

References

References
1.
Holloway
,
D. S.
,
Leylek
,
J. H.
, and
Buck
,
F. A.
,
2002
, “
Pressure-Side Bleed Film Cooling: Part II—Unsteady Framework for Experimental and Computational Results
,”
ASME
Paper No. GT2002-30472. 10.1115/GT2002-30472
2.
Martini
,
P.
,
Schulz
,
A.
,
Bauer
,
H.
, and
Whitney
,
C.
,
2006
, “
Detached Eddy Simulation of Film Cooling Performance on the Trailing Edge Cutback of Gas Turbine Airfoils
,”
ASME J. Turbomach.
,
128
, pp.
292
299
.10.1115/1.2137739
3.
Joo
,
J.
, and
Durbin
,
P.
,
2009
, “
Simulation of Turbine Blade Trailing Edge Cooling
,”
ASME J. Fluids Eng.
,
131
, pp.
1
14
.10.1115/1.3054287
4.
Taslim
,
M.
,
Spring
,
S.
, and
Mehlman
,
B.
,
1992
, “
Experimental Investigation of Film Cooling Effectiveness for Slots of Various Exit Geometries
,”
J. Thermophys. Heat Transfer
,
6
(
2
), pp.
302
307
.10.2514/3.359
5.
Holloway
,
D. S.
,
Leylek
,
J. H.
, and
Buck
,
F. A.
,
2002
, “
Pressure-Side Bleed Film Cooling: Part I—Steady Framework for Experimental and Computational Results
,”
ASME
Paper No. GT2002-30471. 10.1115/GT2002-30471
6.
Martini
,
P.
,
Schulz
,
A.
, and
Bauer
,
H.
,
2006
, “
Film Cooling Effectiveness and Heat Transfer on the Trailing Edge Cutback of Gas Turbine Airfoils With Various Internal Cooling Designs
,”
ASME J. Turbomach.
128
, pp.
196
205
.10.1115/1.2103094
7.
Cunha
,
F.
, and
Chyu
,
M.
,
2006
, “
Trailing-Edge Cooling for Gas Turbines
,”
J. Propul. Power
,
22
(
2
), pp.
286
300
.10.2514/1.20898
8.
Choi
,
J.
,
Mhetras
,
S.
,
Lau
,
S.
, and
Rudolph
,
R.
,
2008
, “
Film Cooling and Heat Transfer on Two Cutback Trailing Edge Models With Internal Perforated Blockages
,”
ASME J. Heat Transfer
,
130
, pp.
1
13
.10.1115/1.2780174
9.
Dannhauer
,
A.
,
2009
, “
Investigation of Trailing Edge Cooling Concepts in a High Pressure Turbine Cascade: Analysis of the Adiabatic Film Cooling Effectiveness
,”
ASME
Paper No. GT2009-59343. 10.1115/GT2009-59343
10.
Krueckels
,
J.
,
Gritsch
,
M.
, and
Schnieder
,
M.
,
2009
, “
Design Considerations and Validation of Trailing Edge Pressure Side Bleed Cooling
,”
ASME
Paper No. GT2009-59161. 10.1115/GT2009-59161
11.
Fiala
,
N.
,
Jaswal
,
I.
, and
Ames
,
F.
,
2010
, “
Letterbox Trailing Edge Heat Transfer: Effects of Blowing Rate, Reynolds Number, and External Turbulence on Heat Transfer and Film Cooling Effectiveness
,”
ASME J. Turbomach.
,
132
, pp.
1
10
.10.1115/1.3195035
12.
Elkins
,
C.
, and
Alley
,
M.
,
2007
, “
Magnetic Resonance Velocimetry: Applications of Magnetic Resonance Imaging in the Measurement of Fluid Motion
,”
Exp. Fluids
,
43
, pp.
823
858
.10.1007/s00348-007-0383-2
13.
Benson
,
M.
,
2011
, “
Measurements of 3D Velocity and Scalar Field for a Film-Cooled Airfoil Trailing Edge
,” dissertation,
Stanford University
,
Stanford, CA
.
14.
Benson
,
M.
,
Elkins
,
C.
,
Mobley
,
P.
,
Alley
,
M.
, and
Eaton
,
J.
,
2010
, “
Three Dimensional Concentration Field Measurements in a Mixing Layer Using Magnetic Resonance Imaging
,”
Exp. Fluids
,
49
(
1
), pp.
43
55
.10.1007/s00348-009-0763-x
15.
Elkins
,
C. J.
,
Markl
,
M.
,
Pelc
,
N.
, and
Eaton
,
J.
,
2003
, “
4D Magnetic Resonance Velocimetry for Mean Velocity Measurements in Complex Turbulent Flows
,”
Exp. Fluids
,
34
(
4
), pp.
494
503
.10.1007/s00348-003-0587-z
16.
Baldauf
,
S.
, and
Scheurlen
,
M.
,
2002
, “
Correlation of Film-Cooling Effectiveness From Thermographic Measurements at Enginelike Conditions
,”
ASME J. Turbomach.
,
124
, pp.
686
698
.10.1115/1.1504443
17.
Chen
,
Y.
,
Matalanis
,
C.
, and
Eaton
,
J.
,
2008
, “
High Resolution PIV Measurements Around a Model Turbine Blade Trailing Edge Film-Cooling Breakout
,”
Exp. Fluids
,
44
, pp.
199
209
.10.1007/s00348-007-0391-2
18.
Laskowski
,
G.
, and
Felten
,
F.
,
2010
, “
Steady and Unsteady CFD Simulations of Transonic Turbine Vane Wakes With Trailing Edge Cooling
,”
European Conference on Computational Fluid Dynamics
, Lisbon, Portugal, June 14–17.
19.
Burns
,
W.
, and
Stollery
,
J.
,
1968
, “
The Influence of Foreign Gas Injection and Slot Geometry on Film Cooling Effectiveness
,”
Int. J. Heat Mass Transfer
,
12
, pp.
935
951
.10.1016/0017-9310(69)90156-2
20.
Bittlinger
,
G.
,
Schulz
,
A.
, and
Wittig
,
S.
,
1994
, “
Film Cooling Effectiveness and Heat Transfer Coefficients for Slot Injection at High Blowing Ratios
,” ASME Paper No. GT1994-182.
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