The aerodynamic performance of a cavity-winglet tip is investigated in a high-pressure turbine cascade by experimental and numerical methods. The winglet tip has geometric features of a cavity and a suction side fore-part winglet. A cavity tip is studied as the baseline case. The aerodynamic performances of the two tips are investigated at three tip gaps of 0.8%, 1.7%, and 2.7% chord. At tip gaps of 1.7% and 2.7% chord, the loss near the blade tip is dominated by the tip leakage vortex (TLV) for both tips, and the winglet tip mainly reduces the loss generated by the tip leakage vortex. In the past, it was concerned that at a small tip gap, the winglet tip could introduce extra secondary loss and show little aerodynamic benefits. The winglet tip used in the current study is also found to be able to effectively reduce the loss at the smallest tip gap size of 0.8% chord. This is because at this small tip gap, the tip leakage vortex and the passage vortex (PV) appear simultaneously for the cavity tip. The winglet tip is able to reduce the pitchwise pressure gradient in the blade passage, which tends to suppress the formation of the passage vortex. The effects of the winglet tip on the flow physics and the loss mechanisms are explained in detail.

References

References
1.
Denton
,
J. D.
,
1993
, “
Loss Mechanisms in Turbomachines
,”
ASME
Paper No. 93-GT-435.
2.
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 Cascades
,”
ASME J. Turbomach.
,
114
(
3
), pp.
643
651
.
3.
Key
,
N. L.
, 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
.
4.
Lee
,
S. W.
, and
Kim
,
S. U.
,
2010
, “
Tip Gap Height Effects on the Aerodynamic Performance of a Cavity Squealer Tip in a Turbine Cascade in Comparison With Plane Tip Results—Part 1: Tip Gap Flow Structure
,”
Exp. Fluids
,
49
(
5
), pp.
1039
1051
.
5.
Lee
,
S. W.
, and
Choi
,
M. Y.
,
2010
, “
Tip Gap Height Effects on the Aerodynamic Performance of a Cavity Squealer Tip in a Turbine Cascade in Comparison With Plane Tip Results—Part 2: Aerodynamic Losses
,”
Exp. Fluids
,
49
(
3
), pp.
713
723
.
6.
Patel
,
K. V.
,
1980
, “
Research on a High Work Axial Gas Generator Turbine
,”
SAE
Paper No. 800618.
7.
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
.
8.
Harvey
,
N. W.
, and
Ramsden
,
K.
,
2001
, “
A Computational Study of a Novel Turbine Rotor Partial Shroud
,”
ASME J. Turbomach.
,
123
(
3
), pp.
534
543
.
9.
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.
10.
Schabowski
,
Z.
,
Hodson
,
H.
,
Giacche
,
D.
,
Power
,
B.
, and
Stokes
,
M. R.
,
2014
, “
Aeromechanical Optimization of a Winglet-Squealer Tip for an Axial Turbine
,”
ASME J. Turbomach.
,
136
(
7
), p.
071004
.
11.
Booth
,
T. C.
,
Dodge
,
P. R.
, and
Hepworth
,
H. K.
,
1982
, “
Rotor-Tip Leakage—Part I: Basic Methodology
,”
ASME J. Eng. Power
,
104
(
1
), pp.
154
161
.
12.
Cheon
,
J. H.
, and
Lee
,
S. W.
,
2015
, “
Tip Leakage Aerodynamics Over the Cavity Squealer Tip Equipped With Full Coverage Winglets in a Turbine Cascade
,”
Int. J. Heat Fluid Flow
,
56
, pp.
60
70
.
13.
Lee
,
S. W.
,
Kim
,
S. U.
, and
Kim
,
K. H.
,
2012
, “
Aerodynamic Performance of Winglets Covering the Tip Gap Inlet in a Turbine Cascade
,”
Int. J. Heat Fluid Flow
,
34
, pp.
36
46
.
14.
Dey
,
D.
, and
Camci
,
C.
,
2001
, “
Aerodynamic Tip Desensitization of an Axial Turbine Rotor Using Tip Platform Extensions
,”
ASME
Paper No. 2001-GT-0484.
15.
Schabowski
,
Z.
, and
Hodson
,
H.
,
2014
, “
The Reduction of Over Tip Leakage Loss in Unshrouded Axial Turbines Using Winglet and Squealers
,”
ASME J. Turbomach.
,
136
(
4
), p.
041001
.
16.
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
.
17.
Tallman
,
J.
, and
Lakshminarayana
,
B.
,
2001
, “
Numerical Simulation of Tip Leakage Flows in Axial Flow Turbines, With Emphasis on Flow Physics—Part I: Effect of Tip Clearance Height
,”
ASME J. Turbomach.
,
123
(
2
), pp.
314
323
.
18.
Palafox
,
P.
,
Oldfield
,
M. L. G.
,
LaGraff
,
J. E.
, and
Jones
,
T. V.
,
2008
, “
PIV Maps of Tip Leakage and Secondary Flow Fields on a Low Speed Turbine Blade Cascade With Moving Endwall
,”
ASME J. Turbomach.
,
130
(
1
), p.
011001
.
19.
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 of Fluid Dynamics, Sint-Genesius-Rode, Belgium.
20.
Yaras
,
M. I.
,
Sjolander
,
S. A.
, and
Kind
,
R. J.
,
1992
, “
Effects of Simulated Rotation on Tip Leakage in a Planar Cascade of Turbine Blades—Part II: Downstream Flow Field and Blade Loading
,”
ASME J. Turbomach.
,
114
(
3
), pp.
660
667
.
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