An accurate assessment of unsteady interactions in turbines is required, so that this may be taken into account in the design of the turbine. This assessment is required since the efficiency of the turbine is directly related to the contribution of unsteady loss mechanisms. This paper presents unsteady entropy measurements in an axial turbine. The measurements are conducted at the rotor exit of a one–and-one-half-stage unshrouded turbine that is representative of a highly loaded, high-pressure stage of an aero-engine. The unsteady entropy measurements are obtained using a novel miniature fast-response probe, which has been developed at ETH Zurich. The entropy probe has two components: a one-sensor fast-response aerodynamic probe and a pair of thin-film gauges. The probe allows the simultaneous measurement of the total temperature and the total pressure from which the time-resolved entropy field can be derived. The measurements of the time-resolved entropy provide a new insight into the unsteady loss mechanisms that are associated with the unsteady interaction between rotor and stator blade rows. A particular attention is paid to the interaction effects of the stator wake interaction, the secondary flow interaction, and the potential field interaction on the unsteady loss generation at the rotor exit. Furthermore, the impact on the turbine design of quantifying the loss in terms of the entropy loss coefficient, rather than the more familiar pressure loss coefficient, is discussed in detail.

1.
Wisler
,
D. C.
, 1998, “
The Technical and Economic Relevance of Understanding Blade Row Interaction Effects in Turbomachinery
,”
Blade Row Interference Effects in Axial Turbomachinery Stages
(
VKI LS 1998–02
),
von Karman Institute for Fluid Dynamics
,
Rhode-St. Genèse, Belgium
.
2.
Sharma
,
O. P.
,
Pickett
,
G. F.
, and
Ni
,
R. H.
, 1992, “
Assessment of Unsteady Flows in Turbines
,”
ASME J. Turbomach.
0889-504X,
114
, pp.
79
90
.
3.
Binder
,
A.
,
Forster
,
W.
,
Mach
,
K.
, and
Rogge
,
H.
, 1986, “
Unsteady Flow Interaction Caused by Stator Secondary Vortices in a Turbine Rotor
,” ASME Paper No. 86-GT-302.
4.
Hodson
,
H. P.
, and
Dawes
,
W. N.
, 1998, “
On the Interpretation of Measured Profile Losses in Unsteady-Turbine Blade Interaction Studies
,”
ASME J. Turbomach.
0889-504X,
120
, pp.
276
284
.
5.
Miller
,
R. J.
,
Moss
,
R. W.
,
Ainsworth
,
R. W.
, and
Horwood
,
C. K.
, 2003, “
Time-Resolved Vane-Rotor Interaction in a High-Pressure Turbine Stage
,”
ASME J. Turbomach.
0889-504X,
125
, pp.
1
13
.
6.
Walreavens
,
R. E.
, and
Gallus
,
H. E.
, 1995, “
Stator–Rotor-Stator Interaction in an Axial Flow Turbine and Its Influence on Loss Mechanisms
,”
AGARD-CP-571, 85th Meeting on Loss Mechanisms and Unsteady Flows in Turbomachinery
, Paper No. 39.
7.
Greitzer
,
E. M.
,
Tan
,
C. S.
, and
Graf
,
M. B.
, 2004,
Internal Flow: Concepts and Applications
,
Cambridge University Press
,
Cambridge, UK
.
8.
Denton
,
J. D.
, 1993, “
Loss Mechanisms in Turbomachines
,”
ASME J. Turbomach.
0889-504X,
115
, pp.
621
652
.
9.
Ng
,
W. F.
, and
Epstein
,
A. H.
, 1984, “
Unsteady Losses in Transonic Compressors
,” ASME Paper No. 84-GT-183.
10.
Payne
,
S. J.
,
Ainsworth
,
R. W.
,
Miller
,
R. J.
,
Moss
,
R. W.
, and
Harvey
,
N. W.
, 2003, “
Unsteady Loss in a High Pressure Turbine Stage
,”
Int. J. Heat Fluid Flow
0142-727X,
24
, pp.
698
708
.
11.
Brouckeart
,
J. F.
, 1998, “
Experience With a Double-Hot-Wire Aspirating Probe in a Transonic Turbine Stage
,”
Proceedings of the 14th Symposium on Measuring Technique for Transonic and Supersonic Flows Cascades in Turbomachines
, Limerick.
12.
Buttsworth
,
D. R.
,
Jones
,
T. V.
, and
Chana
,
K. S.
, 1998, “
Unsteady Total Temperature Measurements Downstream of a High-Pressure Turbine
,”
ASME J. Turbomach.
0889-504X,
120
, pp.
760
766
.
13.
Buttsworth
,
D. R.
, and
Jones
,
T. V.
, 1998, “
A Fast-Response High Spatial Resolution Total Temperature Probe Using a Pulsed Heating Technique
,”
ASME J. Turbomach.
0889-504X,
120
, pp.
601
607
.
14.
Passaro
,
A.
,
LaGraff
,
J. E.
,
Oldfield
,
M. L. G.
,
Biagioni
,
L.
,
Moss
,
R. W.
, and
Battelle
,
R. J.
, 2003, “
Measurements of Turbulent Pressure and Temperature Fluctuation in Gas Turbine Combustor
,”
NASA
, Report No. NASA-CR-2003-212540.
15.
Chana
,
K. S.
, 2004, “
Requirements for Instrumentation Technology for Gas Turbine Propulsion Systems—Gas Total Surface Temperature Measurements for Harsh Environments
,”
Advanced Measurement Techniques for Aeroengines and Stationary Gas Turbines
(
VKI LS 2004–04
),
von Karman Institute for Fluid Dynamics
,
Rhode-St. Genèse, Belgium
.
16.
Mansour
,
M.
,
Chokani
,
N.
,
Kalfas
,
A. I.
, and
Abhari
,
R. S.
, 2008, “
Unsteady Entropy Measurements in a High-Speed Radial Compressor
,”
ASME J. Eng. Gas Turbines Power
0742-4795,
130
, p.
021603
.
17.
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.
0889-504X,
129
, pp.
348
359
.
18.
Schuepbach
,
P.
,
Abhari
,
R. S.
,
Rose
,
M. G.
,
Germain
,
T.
,
Raab
,
I.
, and
Gier
,
J.
, 2008, “
Performance Sensitivity of a High Work Turbine to Purge Flow and Endwall Profiling
,” ASME Paper No. 2008-GT-50471.
19.
Chaluvadi
,
V. S. P.
,
Kalfas
,
A. I.
,
Hodson
,
H. P.
,
Ohyama
,
H.
, and
Watanabe
,
E.
, 2003, “
Blade Row Interaction in a High-Pressure Steam Turbine
,”
ASME J. Turbomach.
0889-504X,
125
, pp.
14
24
.
20.
Schuepbach
,
P.
,
Abhari
,
R. S.
,
Rose
,
M. G.
,
Germain
,
T.
,
Raab
,
I.
, and
Gier
,
J.
, 2008, “
Improving Efficiency of a High Work Turbine Using Non-Axisymmetric Endwalls. Part II: Time-Resolved Flow Physics
,” ASME Paper No. 2008-GT-50470.
21.
Kerrebrock
,
J. L.
, and
Mikolajczak
,
A. A.
, 1970, “
Intra Stator Transport of Rotor Wakes and Its Effect on Compressor Performance
,”
ASME J. Eng. Power
0022-0825,
92
, pp.
359
370
.
22.
Porreca
,
L.
,
Hollenstein
,
M.
,
Kalfas
,
A.
, and
Abhari
,
R.
, 2007, “
Turbulence Measurements and Analysis in a Multistage Axial Turbine
,”
J. Propul. Power
0748-4658,
23
, pp.
227
234
.
You do not currently have access to this content.