Optimization of blade stacking in the last stage of low-pressure (LP) steam turbines constitutes one of the most delicate and time-consuming parts of the design process. This is the first of two papers focusing on the stacking strategies applied to the last stage guide vane (G0). Following a comprehensive review of the main features that characterize the LP last stage aerodynamics, the three-dimensional (3D) computational fluid dynamics (CFD) code used for the investigation and options related to the modeling of wet steam are described. Aerodynamic problems related to the LP last stage and the principles of 3D stacking are reviewed in detail. In this first paper, the results of a systematic study on an isolated LP stator row are used to elucidate the effects of stacking schemes, such as lean, twist, sweep, and hub profiling. These results show that stator twist not only has the most powerful influence on the reaction variation but it also produces undesirable spanwise variations in angular momentum at stator exit. These may be compensated by introducing a positive stagnation pressure gradient at entry to the last stage.

References

1.
McBean
,
I.
,
Havakechian
,
S.
, and
Masserey
,
P. A.
,
2010
, “
The Development of Last Stage Steam Turbine
,”
ASME
Paper No. GT2010-22747.
2.
Havakechian
,
S.
, and
Denton
,
J.
,
2015
, “
3D Blade Stacking Strategy and Understanding of Flow Physics in Low Pressure Steam Turbines: Part II—Equivalence and Differentiators
,”
ASME
Paper No. GT2015-44125.
3.
Sédille
,
M.
,
1966
,
Turbine à Vapeur
, Cours de Conservatoire National des Arts et Métiers, Paris, Chap. 7.
4.
Horlock
,
J. H.
,
1966
,
Axial Flow Turbines
,
Butterworths
,
Oxford, UK
, Chap. 5.
5.
Houberecht
,
A.
,
1972
,
Les Turbines
,
Vendure, Leuven
,
Belgium
, Chap. 5.
6.
Traupel
,
W.
,
1977
, “
Thermische Turbomaschinen
,”
Band I, Thermodynamisch—Strömungstechnische Berechnung, Dritte Auflage
,
Springer-Verlag
,
Berlin
, Chap. 7.
7.
Dejc
,
M. E.
, and
Trojanovskij
,
B. M.
,
1973
,
Untersuchung und Berechnung Axialer Turbinenestufen
,
VEB Verlag Technik
,
Berlin
.
8.
Denton
,
J. D.
,
1991
, “
The Calculation of Three-Dimensional Viscous Flow Through Multistage Turbomachines
,”
ASME J. Turbomach.
,
114
(
1
), pp.
18
26
.
9.
Denton
,
J. D.
,
1993
, “
The 1993 IGTI Scholar Lecture: Loss Mechanism in Turbomachines
,”
ASME J. Turbomach.
,
115
(
4
), pp.
621
656
.
10.
Denton
,
J. D.
, and
Xu
,
L.
,
1999
, “
The Exploitation of 3D Flow in Turbomachinery Design
,”
Proc. Inst. Mech. Eng., Part C
,
213
(
2
), pp.
125
137
.
11.
Weiss
,
A.
,
1998
, “
Aerodynamic Design of Advanced LP Steam Turbines
,”
ABB Rev.
,
5
, pp.
4
11
.
12.
Stüer
,
H.
,
Truckenmüller
,
F.
,
Borthwick
,
D.
, and
Denton
,
J. D.
,
2005
, “
Aerodynamic Concept for Very Large Steam Turbine Last Stages
,”
ASME
Paper No. GT2005-68746.
13.
Pullan
,
G.
, and
Harvey
,
N.
,
2006
, “
The Influence of Sweep on Axial Flow Turbine Aerodynamics at Mid-Span
,”
ASME
Paper No. GT2006-91070.
14.
Pullan
,
G.
, and
Harvey
,
N.
,
2007
, “
The Influence of Sweep on Axial Flow Turbine Aerodynamics in the Endwall Region
,”
ASME
Paper No. GT2007-27750.
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