Cooling at the trailing edge of a gas turbine airfoil is one of the most difficult problems because of its thin shape, high thermal load from both surfaces, hard-to-cool geometry of narrow passages, and at the same time demand for structural strength. In this study, the heat transfer coefficient and film cooling effectiveness on the pressure-side cutback surface was measured by a transient infrared thermography method. Four different cutback geometries were examined: two smooth cutback surfaces with constant-width and converging lands (base and diffuser cases) and two roughened cutback surfaces with transverse ribs and spherical dimples. The Reynolds number of the main flow defined by the mean velocity and two times the channel height was 20,000, and the blowing ratio was varied among 0.5, 1.0, 1.5, and 2.0. The experimental results clearly showed spatial variation of the heat transfer coefficient and the film cooling effectiveness on the cutback and land top surfaces. The cutback surface results clearly showed periodically enhanced heat transfer due to the periodical surface geometry of ribs and dimples. Generally, the increase of the blowing ratio increased both the heat transfer coefficient and the film cooling effectiveness. Within the present experimental range, the dimple surface was a favorable cutback-surface geometry because it gave the enhanced heat transfer without deterioration of the high film cooling effectiveness.

References

References
1.
Cunha
,
F. J.
, and
Chyu
,
M. K.
, 2006, “
Trailing-Edge Cooling for Gas Turbines
,”
J. Propul. Power
,
22
(
2
), pp.
286
300
.
2.
Taslim
,
M. E.
,
Spring
,
S. D.
, and
Mehlman
,
B. P.
, 1992, “
Experimental Investigation of Film Cooling Effectiveness for Slots of Various Exits Geometries
,”
J. Thermophys. Heat Transfer
,
6
(
2
), pp.
302
307
.
3.
Holloway
,
D. S.
,
Leylek
,
J. H.
, and
Buck
,
F. A.
, 2002, “
Pressure Side Film Cooling. Part 2: Unsteady Framework for Experimental and Computational Results
,” ASME Paper No. GT2002-30472.
4.
Martini
,
P.
,
Schulz
,
A.
,
Bauer
,
H.-J.
, and
Whitney
,
C. F.
, 2005, “
Detached Eddy Simulation of Film Cooling Performance on the Trailing Edge Cut-Back of Gas Turbine Airfoils
,” ASME Paper No. GT2005-68084.
5.
Kim
,
Y. W.
,
Coon
,
C.
, and
Moon
,
H.-K.
, 2005, “
Film-Cooling Characteristics of Pressure-Side Discharge Slots in an Accelerating Mainstream Flow
,” ASME Paper No. GT2005-69061.
6.
Fiala
,
N. J.
,
Jaswal
,
I.
, and
Ames
,
F. E.
, 2008, “
Letterbox Trailing Edge Heat Transfer–Effects of Blowing Rate, Reynolds Number, and External Turbulence on Heat Transfer and Film Cooling Effectiveness
,” ASME Paper No. GT2008-50474.
7.
Chen
,
S. P.
,
Peiwen
,
W. L.
, and
Chyu
,
M. K.
, 2006, “
Heat Transfer in an Airfoil Trailing Edge Configuration With Shaped Pedestals Mounted Internal Cooling Channel and Pressure Side Cutback
,” ASME Paper No. GT2006-91019.
8.
Cunha
,
F. J.
,
Dahmer
,
M. T.
, and
Chyu
,
M. K.
, 2005, “
Analysis of Airfoil Trailing Edge Heat Transfer and Its Significance in Thermal-Mechanical Design and Durability
,” ASME Paper No. GT2005-68108.
9.
Horback
,
T.
,
Schulz
,
A.
, and
Bauer
,
H.-J.
, 2010, “
Trailing Edge Film Cooling of Gas Turbine Airfoils–External Cooling Performance of Various Internal Pin Fin Configurations
,” ASME Paper No. GT2010-23578.
10.
Okita
,
Y.
, 2010, “
Heat Rejection Enhancing Parts for Turbine Airfoil Trailing Edge
,” Japanese Patent Application No. 2010-043568.
11.
Carslan
,
H. S.
, and
Jaeger
,
J. C.
, 1956,
Conduction of Heat in Solids
,
2nd ed.
,
Oxford University Press
,
New York
, pp. 29–33 and pp.
70
73
.
12.
Metzger
,
D. E.
, and
Larson
,
D. E.
, 1986, “
Use of Melting Point Surface Coatings for Local Convection Heat Transfer Measurements in Rectangular Channel Flows With 90-deg Turns
,”
ASME J. Heat Transfer
,
108
, pp.
48
54
.
13.
Nishida
,
S.
,
Murata
,
A.
,
Saito
,
H.
, and
Iwamoto
,
K.
, 2009, “
Measurement of Heat and Fluid Flow on Surface with Teardrop-Shaped Dimples
,”
Proceedings of Asian Congress on Gas Turbines, Tokyo, Japan, Aug., ACGT 2009-TS41
.
14.
Schneider
,
H.
,
von Terzi
,
D.
, and
Bauer
,
H.-J.
, 2010, “
Large-Eddy Simulations of Trailing-Edge Cutback Film Cooling at Low Blowing Ratio
,”
Int. J. Heat Fluid Flow
,
31
, pp.
767
775
.
15.
ASME
, 1998,
Test Uncertainty: Instruments and Apparatus. ASME Standard PTC 19.1-1998
,
ASME
,
New York
.
16.
Nishida
,
S.
,
Murata
,
A.
,
Saito
,
H.
, and
Iwamoto
,
K.
, 2011, “
Compensation of Three-Dimensional Heat Conduction Inside Wall in Heat Transfer Measurement of Dimpled Surface by Using Transient Technique
,” J. Enhanced Heat Transfer, accepted.
17.
Murata
,
A.
, and
Mochizuki
,
S.
, 2000, “
Large Eddy Simulation with a Dynamic Subgrid-Scale Model of Turbulent Heat Transfer in an Orthogonally Rotating Rectangular Duct With Transverse Rib
,”
Int. J. Heat Mass Transfer
,
43
(
7
), pp.
1243
1259
.
18.
Ekkad
,
S. V.
, and
Han
,
J. C.
, 1997, “
Detailed Heat Transfer Distributions in Two-Pass Square Channels With Rib Turbulators
,”
Int. J. Heat Mass Transfer
,
40
, pp.
2525
2537
.
19.
Murata
,
A.
,
Mochizuki
,
S.
,
Nakamata
,
C.
, and
Okita
,
Y.
, 2008, “
Large Eddy Simulation of Turbulent Heat Transfer in Stationary Channels With Dimples, Protrusions, and Ribs
,”
Int. J. Transp. Phenom.
,
10
(
4
), pp.
323
336
.
You do not currently have access to this content.