Winglet tips are promising candidates for future high-pressure turbine rotors. Many studies found that the design of the suction-side winglet is the key to the aerodynamic performance of a winglet tip, but there is no general agreement on the exact design philosophy. In this paper, a novel suction-side winglet design philosophy in a turbine cascade is introduced. The winglets are obtained based on the near-tip flow field of the datum tip geometry. The suction-side winglet aims to reduce the tip leakage flow particularly in the front part of the blade passage. It is found that on the casing endwall, the pressure increases in the area where the winglet is used. This reduces the tip leakage flow in the front part of the blade passage and the pitchwise pressure gradient on the endwall. As a result, the size of the tip leakage vortex reduces. A surprising observation is that the novel optimized winglet tip design eliminates the passage vortex and results in a further increasing of the efficiency. The tip leakage loss of the novel winglet tip is 18.1% lower than the datum cavity tip, with an increase of tip surface area by only 19.3%. The spanwise deflection of the winglet due to the centrifugal force is small. The tip heat load of the winglet tip is 17.5% higher than that of the cavity tip. Numerical simulation shows that in a turbine stage, this winglet tip increases the turbine stage efficiency by 0.9% mainly by eliminating the loss caused by the passage vortex at a tip gap size of 1.4% chord compared with a cavity tip.

References

References
1.
Denton
,
J. D.
,
1993
, “
Loss Mechanisms in Turbomachines
,”
ASME
Paper No. 93-GT-435.
2.
Liu
,
H. C.
,
Booth
,
T. C.
, and
Tall
,
W. A.
,
1979
, “
An Application of 3-D Viscous Flow Analysis to the Design of a Low-Aspect-Ratio Turbine
,”
ASME
Paper No. 79-GT-53.
3.
Yaras
,
M. I.
, and
Sjolander
,
S. A.
,
1991
, “
Measurements of the Effects of Winglets on Tip-Leakage Losses in a Linear Turbine Cascade
,”
Tenth International Symposium on Air Breathing Engines
, Nottingham, UK, Sept. 1–6, Paper No. ISABE 91-7011, pp.
127
135
.
4.
Harvey
,
N.
,
Newman
,
D.
, and
Haselbach
,
F.
,
2006
, “
An Investigation Into a Novel Turbine Rotor Winglet—Part 1: Design and Model Rig Test Results
,”
ASME
Paper No. GT2006-90456.
5.
Schabowski
,
Z.
,
Hodson
,
H.
,
Giacche
,
D.
, and
Power
,
B.
,
2014
, “
Aeromechanical Optimisation of a Winglet-Squealer Tip for an Axial Turbine
,”
ASME J. Turbomach.
,
136
(
7
), p.
071004
.
6.
Dey
,
D.
, and
Camci
,
C.
,
2001
, “
Aerodynamic Tip Desensitization of an Axial Turbine Rotor Using Tip Platform Extensions
,”
ASME
Paper No. 2001-GT-0484.
7.
Harvey
,
N. W.
,
2004
, “
Aerothermal Implications of Shroudless and Shrouded Blades
,”
Turbine Blade Tip Design and Tip Clearance Treatment
(VKI Lecture Series), von Karman Institute for Fluid Dynamics, Sint-Genesius-Rode, Belgium.
8.
Zhou
,
C.
,
Hodson
,
H.
,
Tibbott
,
I.
, and
Stokes
,
M.
,
2013
, “
Effects of Winglet Geometry on the Aerodynamic Performance of Tip Leakage Flow in a Turbine Cascade
,”
ASME J. Turbomach.
,
135
(
5
), p.
051009
.
9.
Coull
,
J.
,
Atkins
,
N.
, and
Hodson
,
H. P.
,
2014
, “
Winglets for Improved Aerothermal Performance of High Pressure Turbines
,”
ASME J. Turbomach.
,
136
(
9
), p.
091007
.
10.
Camci
,
C.
,
Dey
,
D.
, and
Kavurmacioglu
,
L.
,
2005
, “
Aerodynamics of Tip Leakage Flows Near Partial Squealer Rims in an Axial Flow Turbine Stage
,”
ASME J. Turbomach.
,
127
(
1
), pp.
14
24
.
11.
Schabowski
,
Z.
, and
Hodson
,
H.
,
2014
, “
The Reduction of Over Tip Leakage Loss in Unshrouded Axial Turbines Using Winglets and Squealers
,”
ASME J. Turbomach.
,
136
(
4
), p.
041001
.
12.
Key
,
N.
, and
Arts
,
T.
,
2006
, “
Comparison of Turbine Tip Leakage Flow for Flat Tip and Squealer Tip Geometries at High-Speed Conditions
,”
ASME J. Turbomach.
,
128
(
2
), pp.
213
220
.
13.
Heyes
,
F. J. G.
,
Hodson
,
H. P.
, and
Dailey
,
G. M.
,
1992
, “
The Effect of Blade Tip Geometry on the Tip Leakage Flow in Axial Turbine
,”
ASME J. Turbomach.
,
114
(
3
), pp.
643
651
.
14.
Kwak
,
J. S.
,
Ahn
,
J.
,
Han
,
J. C.
,
Lee
,
C. P.
,
Bunker
,
R. S.
,
Boyle
,
R.
, and
Gaugler
,
R.
,
2003
, “
Heat Transfer Coefficients on the Squealer Tip and Near-Tip Regions of a Gas Turbine Blade With Single or Double Squealer
,”
ASME J. Turbomach.
,
125
(
4
), pp.
778
787
.
15.
Zhou
,
C.
,
2015
, “
Effects of Endwall Motion on Thermal Performance of Cavity Tips With Different Squealer Width and Height
,”
Int. J. Heat Mass Transfer
,
91
, pp.
1248
1258
.
16.
Newton
,
P. J.
,
Lock
,
G. D.
,
Krishnababu
,
S. K.
,
Hodson
,
H. P.
,
Dawes
,
W. N.
,
Hannis
,
J.
, and
Whitney
,
C.
,
2006
, “
Heat Transfer and Aerodynamics of Turbine Blade Tips in a Linear Cascade
,”
ASME J. Turbomach.
,
128
(
2
), pp.
300
309
.
17.
Zhang
,
Q.
,
O'Dowd
,
D.
,
He
,
L.
,
Wheeler
,
A.
,
Ligrani
,
P.
, and
Cheong
,
B.
,
2011
, “
Overtip Shock Wave Structure and Its Impact on Turbine Blade Tip Heat Transfer
,”
ASME J. Turbomach.
,
133
(
4
), p.
041001
.
18.
Rhee
,
D. H.
, and
Cho
,
H. H.
,
2006
, “
Local Heat/Mass Transfer Characteristics on a Rotating Blade With Flat Tip in a Low-Speed Annular Cascade—Part 2: Tip and Shroud
,”
ASME J. Turbomach.
,
128
(
1
), pp.
110
119
.
19.
Yang
,
D.
,
Yu
,
X.
, and
Feng
,
Z.
,
2010
, “
Investigation of Leakage Flow and Heat Transfer in a Gas Turbine Blade Tip With Emphasis on the Effect of Rotation
,”
ASME J. Turbomach.
,
132
(
4
), p.
041010
.
20.
Acharya
,
S.
, and
Moreaux
,
L.
,
2014
, “
Numerical Study of the Flow Past a Turbine Blade Tip: Effect of Relative Motion Between Blade and Shroud
,”
ASME J. Turbomach.
,
136
(
3
), p.
031015
.
21.
Glassman
,
A. J.
,
1972
, “
Turbine Design and Application
,” NASA Special Publication, NASA Lewis Research Center, Cleveland, OH, Report No.
NASA-SP-290
.https://ntrs.nasa.gov/search.jsp?R=19720019035
You do not currently have access to this content.