In this paper the effect of blade-exit Mach number on unshrouded turbine tip-leakage flows is investigated. Previously published experimental data of a high-pressure turbine blade are used to validate a computational fluid dynamics (CFD) code, which is then used to study the tip-leakage flow at blade-exit Mach numbers from 0.6 to 1.4. Three-dimensional (3D) calculations are performed of a flat-tip and a cavity-tip blade. Two-dimensional calculations are also performed to show the effect of various squealer-tip geometries on an idealized tip flow. The results show that as the blade-exit Mach number is increased the tip-leakage flow becomes choked. Therefore the tip-leakage flow becomes independent of the pressure difference across the tip and hence the blade loading. Thus the effect of the tip-leakage flow on overall blade loss reduces at blade-exit Mach numbers greater than 1.0. The results suggest that for transonic blade rows it should be possible to raise blade loading within the tip region without increasing tip-leakage loss.

References

1.
Wheeler
,
A. P. S.
,
Atkins
,
N. R.
, and
He
,
L.
,
2011
, “
Turbine Blade Tip Heat Transfer in Low Speed and High Speed Flows
,”
J. Turbomach
.,
133
(4)
, p.
041025
.10.1115/1.4002424
2.
Harvey
,
N. W.
,
2004
, “
Turbine Blade Tip Design and Tip Clearance Treatment
,”
VKI Lecture Series 2004-02
.
3.
Schabowski
,
Z.
, and
Hodson
,
H.
,
2007
, “
The Reduction of Over Tip Leakage Loss in Unshrouded Axial Turbines Using Winglets and Squealers
,”
ASME
Paper No. GT2007-27623.10.1115/GT2007-27623
4.
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
, pp.
213
221
.10.1115/1.2162183
5.
Hofer
,
T.
, and
Arts
,
T.
,
2009
, “
Aerodynamic Investigation of the Tip Leakage Flow for Blades With Different Tip Squealer Geometries at Transonic Conditions
,”
ASME
Paper No. GT2009-59909.10.1115/GT2009-59909
6.
Willer
,
L.
,
Haselbach
,
F.
,
Newman
,
D. A.
, and
Harvey
,
N. W.
,
2006
, “
An Investigation Into a Novel Turbine Rotor Winglet: Part 2—Numerical Simulation and Experimental Results
,”
ASME
Paper No. GT2006-90459.10.1115/GT2006-90459
7.
Atkins
,
N. R.
,
Thorpe
,
S. J.
, and
Ainsworth
,
R. W.
,
2008
, “
Unsteady Effects on Transonic Turbine Blade-Tip Heat Transfer
,”
ASME
Paper No. GT2008-51177.10.1115/GT2008-51177
8.
Thorpe
,
S. J.
,
Miller
,
R. J.
,
Yoshino
,
S.
,
Ainsworth
,
R. W.
, and
Harvey
,
N. W.
,
2007
, “
The Effect of Work Processes on the Casing Heat Transfer of a Transonic Turbine
,”
ASME J. Turbomach.
,
129
, pp.
84
91
.10.1115/1.2372772
9.
Molter
,
S. M.
Dunn
,
M. G.
,
Haldeman
,
C. W.
,
Bergholz
,
R. F.
, and
Vitt
,
P.
,
2006
, “
Heat-Flux Measurements and Predictions for the Blade Tip Region of a High Pressure Turbine
,”
ASME
Paper No. GT2006-90048.10.1115/GT2006-90048
10.
Paradiso
,
B.
,
Persico
,
G.
,
Gaetani
,
P.
,
Schennach
,
O.
,
Pecnik
,
R.
, and
Woisetschlager
,
J.
,
2008
, “
Blade Row Interaction in a One and a Half Stage Transonic Turbine Focusing on Three Dimensional Effects: Part I—Stator-Rotor Interaction
,”
ASME
Paper No. GT2008-50291.10.1115/GT2008-50291
11.
Behr
,
T.
,
Kalfas
,
A. I.
, and
Abhari
,
R. S.
,
2007
, “
Unsteady Flow Physics and Performance of a One-and-1/2-Stage Unshrouded High Work Turbine
,”
ASME J. Turbomach.
,
129
, pp.
348
359
.10.1115/1.2447707
12.
Shyam
,
V.
,
Ameri
,
A.
, and
Chen
,
J. P.
,
2010
, “
Analysis of Unsteady Tip and Endwall Heat Transfer in a Highly Loaded Transonic Turbine Stage
,”
ASME
Paper No. GT2010-23694.10.1115/GT2010-23694
13.
Kim
,
S. I.
,
Rahman
,
M. H.
, and
Hassan
,
I.
,
2009
, “
Effect of Turbine Inlet Temperature on Blade Tip Leakage Flow and Heat Transfer
,”
ASME
Paper No. GT2009-60143.10.1115/GT2009-60143
14.
Moore
,
J.
,
Moore
,
J. G.
,
Henry
,
G. S.
, and
Chaudhry
,
U.
,
1989
, “
Flow and Heat Transfer in Turbine Tip Gaps
,”
ASME J. Turbomach.
,
111
, pp.
301
309
.10.1115/1.3262269
15.
Moore
,
J.
, and
Elward
,
K. M.
,
1993
, “
Shock Formation in Overexpanded Tip Leakage Flow
,”
ASME J. Turbomach.
,
115
, pp.
392
399
.10.1115/1.2929266
16.
Chen
,
G.
,
Dawes
,
W. N.
, and
Hodson
,
H. P.
,
1993
, “
A Numerical and Experimental Investigation of Turbine Tip Gap Flow
,”
29th Joint Propulsion Conference and Exhibit, Paper No. AIAA 1993-2253
.
17.
Krishnababu
,
S. K.
,
Hodson
,
H. P.
,
Dawes
,
W. N.
,
Newton
,
P. J.
, and
Lock
,
G. D.
,
2009
, “
Numerical and Experimental Investigation of Tip Leakage Flow and Heat Transfer Using Idealised Rotor-Tip Models at Transonic Conditions
,”
Aeronaut. J.
,
113
, pp.
165
175
.
18.
Denton
,
J. D.
,
1993
, “
The 1993 IGTI Scholar Lecture: Loss Mechanisms in Turbomachines
,”
ASME J. Turbomach.
,
115
, p.
621
.10.1115/1.2929299
19.
Kiock
,
R.
,
Lehthaus
,
F.
,
Baines
,
N. C.
, and
Sieverding
,
C. H.
,
1986
, “
The Transonic Flow Through a Plane Turbine Cascade as Measured in Four European Wind Tunnels
,”
ASME J. Eng. Gas Turbines Power
,
108
, p.
277
.10.1115/1.3239900
20.
Deich
,
M. E.
,
1956
, “
Flow of Gas Through Turbine Lattices
,” Paper No.
NACA TM 1393
.
21.
EN ISO
,
2003
, “
Measurement of Fluid Flow by Means of Pressure Differential Devices Inserted in Circular Cross Section Conduits Running Full—Part 2: Orifice Plates
,” EN ISO 5167-2.
22.
Zhang
,
Q.
, and
He
,
L.
,
2012
, “
Over-Tip Choking and Its Implications on Turbine Blade Tip Aerodynamic Performance
,”
AIAA J. Propul. Power, submitted
.
You do not currently have access to this content.