.
[ T i t l e of Invention]
STEAM TURBINE, AND STEAM TURBINE STATIONARY BLADE
[Technical Field]
5 The p r e s e n t invention r e l a t e s t o a steam turbine, and
m o r e p a r t i c u l a r l y , t o a s t a t i o n a r y b l a d e s t r u c t u r e t o e l i m i n a t e
a l i q u i d film generated on a s t a t i o n a r y blade surface so as
t o reducemoving blade erosion due t o c o l l i s i o n of water d r o p l e t s ,
which a r e generated p a r t i c u l a r l y with wet steam, with a moving
10 blade.
[Background A r t ]
In the f i n a l stage of a low pressure turbine or a stage
p r i o r t o the f i n a l stage by 1 or 2 s t a g e s , g e n e r a l l y , the pressure
15 is very low, accordingly, steam as a working f l u i d is in a s t a t e
of wet steam including l i q u e f i e d minute water droplets
(molecules o f t h e v a p o r ) . Themoleculesofthevaporcondensed
and deposited t o the blade surface coalesce t o each other and
form a l i q u i d film on the blade surface. Further, t h e l i q u i d
20 f i l m i s rippeddownwiththesteamofaworkingfluidmainstream,
orflyinthesteamflowagainfromabladetrailingedge. These
water droplets are s p r a y e d t o t h e downstreamas coarse droplets
f a r l a r g e r i n comparisonwith the i n i t i a l l y occurredmolecules
of the vapor. Then the coarse d r o p l e t s a r e brokenup i n t o smaller
25 s i z e , however, flow down while being maintained i n some s i z e .
CI
Then, the coarse droplets do notsharplyturn along the passage
as in the case of steam due to its inertial force, and collide
against the downstreammoving blade at a high speed, which causes
erosiontoerode theblade surface, orcauseslossduetoaction
5 of a force against the rotation of the turbine blade.
Ontheotherhand, conventionally, toprevent theerosive
action by the erosion phenomenon, the end of a moving blade
leading edge is coated with erosion shield formed of a hard
and high-strength material such as stellite. Otherwise, as
10 in the case of Patent Literature 1 (Japanese UnexaminedUtility
Model Application No. Sho 61(1986)-142102), a method of
mitigatinganimpulsiveforceuponcollisionofliquiddroplets
with the blade by formation of a coarse surface by various
irregularity processing on the surface of the blade leading
15 edge is known. Note that the erosion shield cannot be always
set because of its workability. Further, generally, the mere
protection of the blade surface is less than perfect as an erosion
countermeasure, accordingly, it is employed together with
another erosion countermeasure.
2 0 Generally, to reduce the influenceof erosion, it ismost
effective to eliminate liquid droplets themselves. As shown
in PatentLiterature2 (JapaneseUnexaminedPatentApplication
No. Hei l(1989)-110812) and Patent Literature 3 (Japanese
Unexamined Patent Application No. Hei ll(1999)-336503), to
25 eliminate liquid droplets, a method of sucking the liquid film
C
by providing a hollow stationary blade (hollow nozzle) with
a slit in its blade surface and reducing the pressure in the
hollow stationary blade is used. In many cases, these slits
are formed by directly processing the blade surface of a
5 stationarybladestructurehavingahollowstructure. Further,
a s d e s c r i b e d i n P a t e n t L i t e r a t u r e 4 (JapaneseUnexaminedPatent
ApplicationNo. 2007-23895), amethodof processinga slit member
as a separate member and attaching it to a stationary blade
is known.
10
[Citation List]
[Patent Literature]
[Patent Literature 11 Japanese Unexamined Utility Model
Application No. Sho 61 (1986) -142102
15 [Patent Literature 21 Japanese Unexamined Patent Application
No. Hei l(1989) -110812
[Patent Literature 31 Japanese Unexamined Patent Application
No. Hei 11 (1999) -336503
[Patent Literature 41 Japanese Unexamined Patent Application
20 No. 2007-23895
[Summary of Invention]
[Technical Problem]
A tail part, which includes a blade trailing edge, of
25 the blade has an acute shape with a small thickness. Accordingly,
. evenwhenthehollow s t r u c t u r e o f t h e s t a t i o n a r y b l a d e i s formed
by bending one p l a t e and combining i n t h e t a i l p a r t o r when
t h e h o l l o w p a r t is formedbyboringtheinsideofasolidmember,
it is necessary t o form t h e slit from t h e blade s u r f a c e t o t h e
5 bladehollowregionbyprocessingapositionawaytosomeextent
from t h e blade t r a i l i n g edge.
Further, a s described i n Patent L i t e r a t u r e 4 , regarding
I t h e method of processing a slit member a s a s e p a r a t e member
and a t t a c h i n g it t o t h e s t a t i o n a r y blade, t o o b t a i n an acute
10 p r o f i l e near t h e t r a i l i n g edge and t o ensure a r o u t e t o guide
l i q u i d d r o p l e t s from t h e slit t o t h e hollow p a r t , t h e s l i t
formation p o s i t i o n is n e c e s s a r i l y awayto some e x t e n t f r o m t h e
blade t r a i l i n g edge a s i n t h e case of t h e above example.
On t h e o t h e r hand, t o e f f i c i e n t l y e l i m i n a t e t h e l i q u i d
15 film, t h e slit p o s i t i o n is a s i g n i f i c a n t f a c t o r . On t h e
downstream s i d e of t h e s t a t i o n a r y blade, a s t h e steam flow
v e l o c i t y is increased, t h e m o i s t u r e c o n t e n t i n t e g r a t e d on t h e
blade s u r f a c e is increased. Accordingly, when t h e slit
p o s i t i o n is i n a p o s i t i o n defined with t h e blade s t r u c t u r e as
20 i n t h e case of t h e conventional slit processing, it is not
sufficientlyinthedownstreamregionandthereisaprobability
t h a t t h e moisture content is deposited t o t h e blade again even
i n t h e downstream of t h e slit, and forms a l i q u i d f i l m .
Further, s i n c e t h e steam flow v e l o c i t y is i n c r e a s e d i n
25 t h e region where t h e s l i t is provided, t h e r e is a p r o b a b i l i t y
1 -
that the liquid film is ripped down with the steam flow and
flies fromtheblade surface. In this case, even when the slit
is provided for the pressure reduction and suction, it is
impossibletoeliminatethemoisturecontentawayfromtheblade
5 surface.
Accordingly, the object of the present invention is, in
a steam turbine, to reduce the erosive action on a moving blade
I
by erosion and improve the reliability.
I [Solution to Problem]
10 To attain the above-described object, the present
invention is a steam turbine comprising a turbine stage having
stationaryblades andmoving blades providedon the downstream
sideofthestationarybladesinaworkingfluidflowdirection,
wherein the stationary blade is formed in a hollow blade shape
15 by deformation processing a metal plate, and wherein a slit
to guide liquiddroplets depositedto abladewalltotheinside
of the stationary blade is formed in the blade wall by overlaying
an airfoil suction side metal plate and an airfoil pressure
side metal plate with a gap therebetween in the tail part of
20 the stationary blade.
[Advantageous Effects of Invention]
According tothe present invention, since it is possible
to provide a slit to eliminate a liquid film generated on a
blade wall surface of a stationary blade in the vicinity of
25 a trailing edge of the stationary blade and to sufficiently
-
eliminate the liquid film, it is possible to reduce an erosive
action on a moving blade by erosion and to improve the
reliability.
5 [Brief Description of Drawings]
Fig. 1 is a schematic diagram showing the stage of a
conventional steam turbine and a liquid film flowing on a
stationary blade surface.
Fig. 2 is a cross-sectional diagram of a passage between
10 the stationary blades, schematically showing a status where
liquid droplets fly at a blade trailing edge from the liquid
I
I film developed on the stationary blade surface of the
I
I conventional turbine.
I Fig. 3is a schematicperspectivediagramofa stationary
15 bladeaccordingtoa first embodiment ofthepresent invention.
Fig. 4 is a cross-sectional diagram in a position shown
with an alternate long and two short dashes line in Fig. 3.
Fig. 5 is an enlarged diagram of a tail part in Fig. 4.
I Fig. 6 is a diagram showing the relation between the
I 20 thickness of a liquid film generated on a blade surface and I 1
a liquid film flow amount.
Fig. 7 is a schematic perspective diagramof the stationary
bladeaccordingtoasecondembodimentofthepresentinvention.
Fig. 8 is a blade cross-sectional diagramof the stationary
25 bladeaccordingtoathirdembodimentofthepresentinvention.
Fig. 9 is an enlarged diagram of the tail part in Fig.
8.
Fig. 10 is a perspective diagram of a positioning piece.
Fig. 11 is a schematic perspective diagram of the
5 stationary blade according to a fourth embodiment of the present
invention.
F i g . 1 2 i s a c r o s s - s e c t i o n a l d i a g r a m o f a n a r b i t r a r y c r o s s
section of a slit formation part of the stationary blade shown
in Fig. 11.
10 Fig. 13 is a schematic perspective diagram of the
stationaryblade according to a fifth embodiment ofthe present
invention.
F i g . 1 4 i s a c r o s s - s e c t i o n a l d i a g r a m o f a n a r b i t r a r y c r o s s
sectionoftheslitformationpartofthestationarybladeshown
15 in Fig. 13.
[Description of Embodiments]
First, the status of the occurrence of liquid film and
liquid droplets on a turbine blade surface will be briefly
20 described using Figs. 1 and 2.
Fig. 1 is a schematic diagram showing the stage of a
conventional steam turbine and the flow of a liquid film
developed on a wall surface of its stationary blade. The turbine
stage of the steam turbine has stationary blades (nozzles) 1
25 fixed to an outer peripheral side diaphragm 4 and an inner
~ .I
I peripheralsidediaphragm6, andmovingblades (buckets) 2 fixed
t o a rotor shaft 3 on the downstream side of t h e s t a t i o n a r y
blades 1 in a working f l u i d flow direction. A casing 7 forming
a wall surface of the passage is provided on the outer peripheral
5 side a t an end ofthemoving blade 2. With the above structure,
a steammainstreamas a working f l u i d is accelerated upon passing
through the stationaryblade 1, t o provide energytothemoving
blade 2, to r o t a t e the r o t o r s h a f t 3.
In a low pressure turbine o r the l i k e , when the steam
10 mainstream as a working f l u i d steam becomes in a s t a t e of wet
steam, liquid droplets included in the steam mainstream are
deposited to t h e s t a t i o n a r y blade 1, and t h e l i q u i d droplets
congregate on the stationary blade surface t o form a l i q u i d
film. The liquid film flows i n a direction of a force determined
15 with a r e s u l t a n t force between pressure and a shear force in
a boundary surface with respect t o gas steam, and moves t o a
position in the vicinityofthetrailingedge o f t h e stationary
blade. Fig. 1 shows a flow 11 of the moving l i q u i d film. The
liquid filmmoved t o t h e p o s i t i o n in the v i c i n i t y of the t r a i l i n g
20 edge of the blade becomes l i q u i d droplets 13, and f l y together
with the steam mainstream toward the moving blade 2.
Fig. 2 is a cross-sectional diagram of a passage between
t h e s t a t i o n a r y b l a d e s schematically showing a s t a t u s where the
liquid droplets are surface-stripped from t h e l i q u i d film
25 developedontheblade surface o f t h e stationaryblade 1. When
.I
air flow steam 10 passes between the stationary blades, the
liquid droplets are deposited to the stationary blade 1, then
the liquiddroplets congregate on the stationaryblade surface
and is developed into a liquid film 12. The liquid film 12
5 developed on the blade surface of the stationary blade 1 moves
to the blade trailing edge, is surface-stripped and flies as
the liquid droplets 13 from the blade trailing edge. The
surface-strippedliquiddroplets 13 collide against themoving
blade2provideddownstream,tocauseerosiontoerodethemoving
10 blade surface or act a force against the rotation of the moving
blade and cause loss.
In view of the above description, the embodiments of the
present invention will be described in detail below
appropriately with reference to the drawings. Note that
15 corresponding constituent elements in the respective figures
including Figs. 1 and 2 have the same reference numerals.
[Embodiment 11
A first embodiment according to the present invention
will be described.
20 Figs. 3 to 5 are explanatorydiagrams showing the structure
where the preset invention is applied to the stationary blade
1 in Fig. 1. Fig. 3 is a schematic perspective diagram of the
stationary blade 1 according to the present embodiment, Fig.
4, a cross-sectional diagram in a position indicated with an
25 alternate long and two short dashes line in Fig. 3, and Fig.
I
5, an enlarged diagram of a blade t a i l p a r t i n Fig. 4 .
As shown i n Fig. 3, the s t a t i o n a r y blade 1 of the present
embodiment is formed by joining a main body 5 and a blade t a i l
p a r t 8 formed as a separate body of the main body 5 along a
5 welding l i n e 9. As shown i n Fig. 4 , the main body 5 is formed
b y p l a s t i c a l l y deforming a m e t a l p l a t e b y p r e s s i n g or the l i k e ,
and has a hollow blade shape s t r u c t u r e having a hollow p a r t
26 i n s i d e . On the other hand, the t a i l p a r t 8 has a suction
side p l a t e 20 which is a metal p l a t e forming a suction side
10 wallsurfaceofairfoilandapressure s i d e p l a t e 2 1 p l a t e w h i c h
isametalplateformingapressuresidewallsurfaceofairfoil.
The pressure side 21 is attached t o the suction side p l a t e 20
while p o s i t i o n i n g p i e c e 22 t o be described l a t e r is held
therebetween.
15 As shown i n Fig. 10, the p o s i t i o n i n g p i e c e 22 has a
disk-shaped brim 31 which plays a r o l e of spacer and a c y l i n d r i c a l
convex member 34 provided a t both ends of the brim 31. As
described l a t e r , it is possible t o f i x the mutual p o s i t i o n s
of the suction side p l a t e 20 and the pressure side p l a t e 21
20 t o predetermined p o s i t i o n s e a s i l y by i n s e r t i n g t h e both side
convexmembers 34 i n t o piece holes formed as a p a i r i n the suction
side p l a t e 20 and the pressure side p l a t e 21. Further, as the
disk-shaped brim 31 is held between the suction side p l a t e 20
and the pressure side p l a t e 21, a gap corresponding t o the
25 thickness of the brim 31 is formed between the suction side
*
plate 20 and the pressure side plate 21. It is possible to
form a predetermined gap between the suction side plate 20 and
the pressure side plate 21easilyby controlling the thickness
ofthebrim 31. Note that the shapes ofthebrimand the convex
5 member of the positioning piece 22 are not limited to the disk
shape and the cylindrical shape as long as they play the roles
of position fixing and spacer.
Returning tothe description ofthe tail part 8, as shown
in Fig. 5, one end of the suction side plate 20 is welded and
10 fixed to the metal plate of the main body 5 on the suction side
of airfoil, and the other end forms an acute-shaped blade
trailing edge. Further, the surface of the suction side plate
20 on the blade inner surface side is partially cut froma position
away to some extent from the blade trailing edge toward the
15 main body 5 side, thus a step part 27 is provided.
On the other hand, the pressure side plate 21is overlaid
on the step part 27 of the suction side plate 20 with a gap
therebetween. One end of the pressure side plate 21 is welded
and fixed to the metal plate of the main body 5 on the pressure
20 sideof airfoil, andtheotherendthereofhasagapwithrespect
to the step part 27. A slit 24 can be formed by providing the
gap between the step part 27 of the suction side plate 20 and
the end of the pressure side plate 21. The wall of the slit
24 on the blade leading edge side is formed with the end of
25 the pressure side plate 21, and the wall on the blade trailing
C edge side is formed with the suction side p l a t e 20, and opened
in the blade height d i r e c t i o n . For example, i n the example
shown i n Fig. 3, the slit 24 is provided over the e n t i r e length
in the blade height d i r e c t i o n , however, it is not necessary
5 t o provide it over the e n t i r e length i n the blade height d i r e c t i o n .
It may be provided i n a p a r t on t h e o u t e r p e r i p h e r a l side i n
the blade height d i r e c t i o n .
In the suction side p l a t e 20 and the pressure side p l a t e
21, a p a i r of p i e c e h o l e s 29 and 30 where the above-described
10 p o s i t i o n i n g p i e c e 22 is provided are opened. As shown i n Fig.
5, i t i s p o s s i b l e t o f o r m a g a p 2 5 c o r r e s p o n d i n g t o t h e t h i c k n e s s
of the brim 31 of the p o s i t i o n i n g p i e c e 22 between the suction
side p l a t e 20 and the pressure side p l a t e 21 by i n s e r t i n g t h e
p o s i t i o n i n g p i e c e 22 i n t o the piece holes 29 and 30 andholding
15 them between the suction side p l a t e 20 and the pressure side
p l a t e 21. Since the pressure side p l a t e 21 is overlaid on the
s t e p p a r t 27 of the suction side p l a t e 20 with a gap therebetween,
the gap 25 is connected t o the slit 24, t o form a f l u i d channel
t o guide t h e l i q u i d d r o p l e t s flowed i n from the slit 24 t o a
20 hollow p a r t 26.
The pressure s i d e p l a t e 2 1 i s p r o v i d e d w i t h p l u r a l s e c o n d
slits 23 i n the blade height d i r e c t i o n on the upstream side
of the s l i t 24 i n a steam mainstream flow d i r e c t i o n as shown
in Fig. 3. The second slit 23 is formed through the pressure
25 side p l a t e 21 as shown i n Fig. 5. When the pressure side p l a t e
. 21 is attached t o the suction side p l a t e 20, it is connected
t o t h e gap25 between the suction side p l a t e 20 andthe pressure
side p l a t e 21. Accordingly, it is a l s o possible t o guide the
l i q u i d droplets flowed i n from the second s l i t 23 through the
5 gap 25 t o the hollow p a r t 26.
The suction side p l a t e 20 and the pressure side p l a t e
21 are fixed i n s p e c i f i e d p o s i t i o n s and the blade t a i l p a r t
8 is formed i n an i n t e g r a l construction by closing the piece
holes 29 and 30 by welding or hard soldering a f t e r the attachment
10 of the suction side p l a t e 20, the pressure side p l a t e 21 and
t h e p o s i t i o n i n g p i e c e 2 2 . Theupperandlower ends o f t h e b l a d e
t a i l p a r t 8 a r e closed with a cover 33 respectively as shown
in Fig. 3, o r d i r e c t l y welded t o the outer peripheral side
diaphragm 4 and the inner p e r i p h e r a l side diaphragm 6, so as
15 t o prevent leakage of t h e l i q u i d droplets introduced from the
second s l i t 23, the slit 24 and the gap 25.
Note t h a t the piece hole may be provided a t a fixed i n t e r v a l
i n p l u r a l p o s i t i o n s i n the blade height d i r e c t i o n between the
s l i t 24 and the second s l i t 23 as shown in Fig. 3. The piece
20 holes a r e provided i n two p o s i t i o n s on the blade outer peripheral
side and i n one position from the blade center t o the inner
peripheral s i d e s i n c e the blade length is s h o r t . By f i t t i n g
thepositioningpieceintothe r e s p e c t i v e h o l e s , it is possible
t o s t a b l y f i x the suction s i d e p l a t e 20 and the pressure side
25 p l a t e 21. However, the arrangement is not limited t o the example
t
shown i n Fig. 3 a s long a s t h e s u c t i o n s i d e p l a t e 20 and t h e
pressure s i d e p l a t e 21 can be s t a b l y f i x e d . It is p o s s i b l e
t o e a s i l y f i x t h e mutual p o s i t i o n s of t h e s u c t i o n s i d e p l a t e
20 and t h e pressure s i d e p l a t e 21 i n predetermined p o s i t i o n s
5 where t h e slit 24 and t h e gap 25 a r e formed, with t h e piece
holes 29 and 30 provided i n p a i r i n t h e s u c t i o n s i d e p l a t e 20
and t h e pressure s i d e p l a t e 21 and t h e p o s i t i o n i n g p i e c e 22.
Next, t h e i n s t a l l a t i o n p o s i t i o n s of t h e s l i t 24 and t h e
second slit 23 w i l l be described.
10 The l i q u i d f i l m generated on t h e blade s u r f a c e becomes
unstable when t h e steam flow v e l o c i t y is increased, and i t s
p a r t is surface-strippedandflies f r o m t h e b l a d e s u r f a c e . The
unstable phenomenon of t h e l i q u i d f i l m occurs when r e l a t i v e
Weber number Wr=0.5xph(U-W)x(U-W)/o, r e p r e s e n t e d with steam
15 concentration p, l i q u i d f i l m t h i c k n e s s h, steam flow v e l o c i t y
U, l i q u i d f i l m flow v e l o c i t y W and l i q u i d f i l m s u r f a c e tension
o, is equal t o o r g r e a t e r than 0.78. Even when t h e s l i t is
p r o v i d e d i n a p o s i t i o n w h e r e t h i s r e l a t i v e W e b e r n u m b e r i s e q u a l
t o o r g r e a t e r than 0.78, a p a r t of t h e l i q u i d f i l m has been
20 s u r f a c e - s t r i p p e d and has flown i n t h e passage, and it is not
p o s s i b l e t o e f f i c i e n t l y e l i m i n a t e t h e moisture c o n t e n t .
Accordingly, t h e slit 24 and t h e second slit processed and formed
i n t h e b l a d e t a i l p a r t 8 a r e p r o v i d e d i n a p a r t w h e r e t h e r e l a t i v e
Weber number of t h e l i q u i d f i l m flow is 0.78.
2 5 Fig. 6 shows t h e t h i c k n e s s of t h e l i q u i d f i l m generated
on the wall surface and the liquid film thickness (minimum liquid
thickness for surface stripping) whenthe relativewebernumber
is 0.78. The horizontal axis indicates a dimensionless
distance obtained from a distance 1 measured along the blade
5 surface from the airfoil leading edge 32 to the an arbitrary
position of the blade surface shown in Fig. 4, using a distance
L measured along the blade surface from the airfoil leading
edge end 32 to the trailing edge 28. In a position where the
minimumliquid thickness for surface stripping is thinner than
10 the water film thickness generated on the blade surface, the
liquid film cannot be deposited on the blade surface, and it
is impossible to sufficiently eliminate the moisture content
even with the slit. As the slit position shown in Fig. 3, the
I upstream-side second slit 23 is provided in the range of l/L=O. 56
15 to 0.9. The increment of the steam flow velocity is large in
the downstream region fromthe range ofl/L=0.65 to 0.75. Even
though 100% of the liquid film is eliminated with the second
slit 23, a large amount of liquid film is generated again on
its downstream side. The relative Weber number of the liquid
20 filmexceedstheminimumliquidthickness for surface stripping
I
I
again. Therefore, the slit 24 is provided in a position in
the range of 1/L=0.75 to 0.9. The liquid film is generated
inthedownstreamregionofthe slit24, however, it is possible
to eliminate 80% or more of the liquid film generated on the
25 stationary blade surface with the above-described two slits.
Inthe present embodiment, the stationarybladeis formed
as a joint between the main body 5 having the hollow structure
and the blade tail part 8. Further, the blade tail part 8 is
formedbycombining themetal plate on the suction side of airfoil
5 (the airfoil suction-side metal plate) and the metal plate on
the pressure side of airfoil (the airfoil pressure-side metal
plate). In the blade tail part 8, the airfoil suction-side
metal plate and the airfoil pressure-side metal plate are not
directly joined. It is possible to provide a slit in the vicinity
10 of the blade trailing edge by inserting a spacer between the
and the airfoil pressure-side
metal plate and overlaying them so as to form a gap.
In the blade tail part, the pressure side plate
s l i t - p r o c e s s e d i n t h e h e i g h t d i r e c t i o n i s a t t a c f i e d t o t h e s u c t i o n
15 side plate forming the acute part at the trailing edge and the
step part on one surface, so as to hold the positioning piece
therebetween, to form space corresponding to the thickness of
the positioning piece on the inner surface side of the suction
side plate and the pressure side plate. Further, the gap is
20 provided between the one side end surface of the pressure side
plate and the step part of the suction side plate, and the suction
side plate and the pressure side plate are attached so as to
form the slit. It is possible to set the slit position
immediately close to the trailing edge by providing the step
25 part of the suction side plate in a position close to the trailing
edge.
According t o t h e s t r u c t u r e of t h e present embodiment,
s i n c e it is p o s s i b l e t o set t h e p o s i t i o n of t h e slit t o guide
t h e l i q u i d d r o p l e t s deposited on t h e b l a d e w a l l s u r f a c e t o t h e
5 i n s i d e of t h e blade i n a region o f t h e minimum l i q u i d t h i c k n e s s
f o r s u r f a c e s t r i p p i n g , it is p o s s i b l e t o e l i m i n a t e 80% of t h e
l i q u i d f i l m g e n e r a t e d o n t h e s t a t i o n a r y b l a d e , t o r e d u c e e r o s i v e
a c t i o n on t h e moving blade by e r o s i o n , and improve t h e
r e l i a b i l i t y .
10 N o t e t h a t a s t h e b l a d e t a i l p a r t 8 , itmaybemanufactured
i n a s e p a r a t e body from t h e main body a s t h e blade t a i l p a r t
8 from t h e upstream-side p o s i t i o n from t h e second slit 23 on
t h e downstream s i d e of t h e dimensionless d i s t a n c e 1/L=0.5.
[Embodiment 2 1
Next, a second embodiment of t h e p r e s e n t i n v e n t i o n w i l l
b e d e s c r i b e d u s i n g Fig. 7. In t h e present embodiment, t h e s l i t
isnotformedintheentireregioninthestationarybladeheight
d i r e c t i o n , but l i m i t e d l y i n a region opposite t o t h e t i p p a r t
of t h e moving blade 2 shown i n Fig. 1.
2 0 The l i q u i d f i l m is e l i m i n a t e d with t h e slit 24 and t h e
second s l i t 23, however, t h e steam is a l s o sucked a t t h e same
t i m e of t h e e l i m i n a t i o n of t h e l i q u i d f i l m . The increment of
t h e steam removal d i r e c t l y i n f l u e n c e s t h e degradation of t h e
performance o f t h e s t e a m t u r b i n e . Further, t h e erosionamount
25 by t h e l i q u i d d r o p l e t s f l y i n g from t h e s t a t i o n a r y blade is
r
increased in accordance with the increment of the
circumferential velocity of the moving blade. Accordingly,
the blade structure in the 70% or greater region in the blade
height direction is formedwiththe joint body between themain
5 body 5 and the blade tail part 8 shown in the embodiment 1.
In the present embodiment, it is possible to eliminate
the liquid film in a region of large erosion amount, and reduce
the steam removal in the slit, in addition, in a long blade
such as a low-pressure turbine final-stage stationary blade,
10 by limiting the region of the 2-body structure to 30% of the
blade height direction, i.e., a part in the blade height
direction where the liquid film particularly occurs, it is
possible to easily manufacture the structure.
Note that the blade tail part 8 shown in Fig. 3 and Fig.
15 5 is formed using the positioning piece 22, however, the blade
tail part 8 may be formed by precision casting.
[Embodiment 31
Next, athirdembodimentofthepresentinventionis shown
in Fig. 8 and Fig. 9. Fig. 8 shows a cross-section of the
20 stationary blade according to the third embodiment, and Fig.
9 i s a n e n l a r g e d d i a g r a m o f t h e b l a d e t a i l p a r t o f t h e stationary
blade shown in Fig. 8.
In the present embodiment, the blade tail part 8 is not
formed completely independently of the main body 5, but the
25 member forming the blade surface of the main body 5 is extended
w
and applied t o the suction side p l a t e 20 of the blade t a i l p a r t
8. That is, on the suction side of a i r f o i l , the main body 5
and the blade t a i l p a r t 8 are formed with one metal p l a t e . On
the other hand, on the pressure side of a i r f o i l , as in the case
5 of the embodiment 1, the metal p l a t e s forming the main body
5 and the blade t a i l p a r t 8 are separate bodies. The pressure
side p l a t e 21 is overlaid on t h e s t e p p a r t 27 of the suction
side p l a t e 20 i n t e g r a l l y formed with the main body 5 with a
gap therebetween, and i t s one end is welded and fixed t o the
10 metal p l a t e of the main body 5 on the pressure side of a i r f o i l
along the welding l i n e 9. On the other hand, the other end
of the pressure side p l a t e 21 has a gap with respect t o the
s t e p p a r t 27 of the suction side p l a t e 20 i n t e g r a l l y formed
with the main body 5. A s in the case of the embodiment 1, by
15 o v e r l a y i n g t h e s u c t i o n s i d e p l a t e 2 0 a n d t h e p r e s s u r e s i d e p l a t e
21 with a gap therebetween, the s l i t 24 is formed by forming
one wall of the s l i t with the end of the pressure side p l a t e
21 and forming the other wall with the s t e p p a r t of the suction
s i d e p l a t e . It is possible t o form the slit 24 between the
20 s t e p p a r t 2 7 o f t h e s u c t i o n s i d e p l a t e a n d t h e e n d o f t h e p r e s s u r e
side p l a t e 21 by providing the gap.
The method of joining the pressure side p l a t e 21 with
t h e p o s i t i o n i n g p i e c e 2 2 t o t h e s u c t i o n s i d e p l a t e 2 0 i s similar
t o the method shown i n Fig. 3. According t o the present
25 embodiment, i n addition t o the advantage of the embodiment 1,
r as the suction side plate ofthe blade tail part 8 and the metal
plate of the main body 5 is one metal plate, it is possible
to reduce the number of processing steps such as welding and
member cutting and to reduce the erosive action on the moving
5 blade by erosion at a lower cost.
[Embodiment 4 ]
Next, a fourth embodiment of the present invention is
shownin Fig. 11andFig. 12. Fig. 11is a schematicperspective
diagram of the stationary blade according to the present
10 embodiment. Fig. 12 is a cross-sectional diagram of an
arbitrary cross section of a slit formation part in Fig. 11.
The structure of the airfoil shown in Fig. 8 is applied to the
structure of the airfoil in Fig. 11. The pressure side plate
21 of the blade tail part 8 is not formed as a separate member
15 of the main body, but the member forming the blade surface of
the main body is extended and applied.
In the present embodiment, the entire airfoil is
previouslyformedbyemboss-pressprocessingoneplatemember.
Aftertheemboss-pressprocessing,thepressuresideofairfoil
20 is cut in a position sufficiently away from the leading edge,
and the pressure side plate 21 is removed. In the blade tail
part of the suction side plate and the pressure side slit
formation part, the blade plate member is cut in its thickness
direction, to form the outer shape of the airfoil and a gap
25 fluid channel part between the suction side and the pressure
side oftheblade inner surface. Areinforcing rib 36is fixed
by welding or the like to the blade inner side of a cut-out
part 35 of the pressure side plate 21 at the leading edge. The
pressure side plate 21 is fixed by welding on this rib. The
5 blade tail side of the pressure side plate 21 is fixed to the
upstream side of the second slit 23 with the positioning piece
provided between the slit 24 and the second slit 23. Further,
the reinforcing rib 36 is provided with a vent hole 37
communicable with the hollow part 26 divided with the rib 36.
10 By providing the vent hole 37, it is possible to uniform the
pressure of the blade hollow part and to mitigate the load due
to the pressure acting on the reinforcing rib 36.
In the present embodiment, in addition tothe advantages
of the embodiment 1 and the embodiment 3, the strength of the
15 structure of the hollow blade is increased by providing the
reinforcing rib 36 inside the blade.
[Embodiment 51
Next, a fifth embodiment of the present invention will
be described using Fig. 13 and Fig. 14. Fig. 13 is a schematic
20 perspective diagram of the stationary blade according to the
present embodiment. Fig. 14 is a cross-sectional diagram of
an arbitrary cross section of the slit formation part of the
stationary blade shown in Fig. 13. In the embodiment shown
in Fig. 5 or Fig. 9, the positioning piece shown in Fig. 10
25 is used so as to fix the suction side plate and the pressure
*
s i d e p l a t e and t o ensure t h e s i z e o f t h e gapbetween t h e s u c t i o n
s i d e p l a t e and t h e p r e s s u r e s i d e p l a t e . In t h e present
embodiment, i n place of t h e p o s i t i o n i n g piece, a r i b 40 formed
i n s i d e t h e s u c t i o n s i d e p l a t e is provided.
5 In t h e s u r f a c e on t h e blade i n n e r s i d e of t h e s u c t i o n
s i d e p l a t e 20, a concave p a r t forming a gap p o r t i o n through
which t h e water f i l m flow sucked from t h e slit flows is formed
by engraving. Further, t h e r i b 40 is provided i n a d i r e c t i o n
along t h e flow d i r e c t i o n of t h e steam mainstream i n p l u r a l
10 p o s i t i o n s i n t h e concave member i n t h e blade height d i r e c t i o n .
A gap f l u i d channel having a width o f t h e height of t h e r i b
40 is formedbetweenthe s u c t i o n s i d e p l a t e 20 and t h e pressure
s i d e p l a t e 21 by j o i n i n g t h e p r e s s u r e s i d e p l a t e 21 t o t h e r i b
40 when t h e s u c t i o n s i d e p l a t e 20 and t h e pressure s i d e p l a t e
15 21 a r e o v e r l a i d . Note t h a t t h e p r e s s u r e s i d e p l a t e 21 is provided
so a s t o cover t h e r i b 40 and is f i x e d by welding o r t h e l i k e .
According t o t h e p r e s e n t embodiment, t h e w i d t h o f t h e gap f l u i d
channel can be c o n t r o l l e d by c o n t r o l l i n g t h e r i b h e i g h t .
N o t e t h a t i n t h e e m b o d i m e n t i n F i g . 1 3 , t h e r i b i s p r o v i d e d
20 on t h e i n n e r s u r f a c e of t h e s u c t i o n s i d e p l a t e 20, however,
it may be provided on t h e i n n e r s u r f a c e s i d e of t h e pressure
s i d e p l a t e 21. Further, t h e s t a t i o n a r y blade shown i n Fig.
13 is an example where i n t h e s t a t i o n a r y b l a d e e x p l a i n e d i n
theembodiment2,therib40ofthepresentembodimentisapplied
25 i n place of t h e p o s i t i o n i n g p i e c e . The r i b 40 of t h e present
embodiment in place of the positioning piece may be applied
in the stationary blade of the embodiment 1, the embodiment
3 or the embodiment 4.
In the present embodiment, as in the case of the other
5 embodiments, it is possibleto seta position immediately close
tothetrailingedge as the slit position, toreduce theerosive
action on the moving blade by erosion and to improve the
reliability. In addition, as a part completelyseparatedfrom
the suction side plate and the pressure side plate such as the
10 positioningpieceisnotrequiredforformationofthegapfluid
channel and joint between the suction side plate and the pressure
side plate, it is possible to reduce the manufacturing cost
of the hollow stationary blade by reduction of the number of
assembly parts and reduction of the number of assembly steps.
[Reference Signs List]
1 stationary blade
2 moving blade
5 main body
20 8 blade tail part
20 suction side plate
21 pressure side plate
22 positioning piece
23 second slit
25 24 slit
25 gap
26 hollow p a r t
27 s t e p p a r t
28 t r a i l i n g edge
5 2 9 p i e c e h o l e
30 piece hole
31 brim
32 leading edge of a i r f o i l
34 convex member
10 36 r i b
37 vent hole
40 r i b

We claim:
[Claim 11
A steam turbine comprising a turbine stage having a
stationaryblade, withaslittoguideliquiddropletsdeposited
5 on a blade wall surface t o t h e i n s i d e of the stationary blade,
in the blade wall surface, and a moving blade provided on the
downstreamside o f t h e s t a t i o n a r y b l a d e i n a working f l u i d flow
direction,
wherein the stationary blade is a hollow-blade shaped
10 stationaryblade formedby deformation processing ametal p l a t e ,
and
wherein a blade t a i l part of the stationary blade has
the slit formed by overlaying an a i r f o i l suction-side metal
plate and an a i r f o i l pressure-side metal p l a t e with a gap
15 therebetween.
[Claim 21
Thesteamturbineaccordingtoclaim1, furthercomprising
second slits provided in a p l u r a l i t y of positions in a blade
h e i g h t d i r e c t i o n o n t h e u p s t r e a m s i d e o f t h e s l i t i n a m a i n s t r e a m
20 flow direction,
wherein the second slits are connected t o a gap provided
between the a i r f o i l suction-side metal p l a t e and the a i r f o i l
pressure-side metal p l a t e .
[Claim 31
The steam turbine according t o claim 2,
wherein the slit and the second slits are provided on
the pressure side of a i r f o i l , and
wherein the second slits are provided i n a p o s i t i o n i n
a range of 0.65 t o 0.75 as 1 / L r a t i o between a d i s t a n c e 1 along
5 ablade surface fromthe a i r f o i l leading edge o f t h e s t a t i o n a r y
blade t o an a r b i t r a r y p o s i t i o n of the blade surface anda distance
L along the blade surface from the a i r f o i l leading edge t o the
t r a i l i n g e d g e o f t h e s t a t i o n a r y b l a d e , .and the s l i t is provided
i n a potion i n a range of 0.75 t o 0.9 as the 1 / L r a t i o .
10 [Claim 41
The steam turbine according t o any one of claims 1 t o
3, f u r t h e r comprising:
a p a i r o f p i e c e h o l e s p r o v i d e d i n t h e a i r f o i l s u c t i o n - s i d e
metal p l a t e and the a i r f o i l pressure-side metal p l a t e ;
15 a p o s i t i o n i n g piece having a spacer, held between the
airfoilsuction-sidemetalplateandtheairfoilpressure-side
metal p l a t e , t o form a gap, and a convex member, provided a t
both ends of the spacer and inserted in the piece holes, t o
f i x mutual positions of the a i r f o i l suction-side metal p l a t e
20 and the a i r f o i l pressure-side metal p l a t e , and
a step p a r t , provided on the blade i n n e r surface side
of the a i r f o i l suction-sidemetal p l a t e , overlaid on the t r a i l i n g
edge side end of the a i r f o i l pressure-side metal p l a t e with
a gap therebetween, t o form the slit.
25 [Claim 51
The steam turbine according to any one of claims 1 to
4, wherein the and the airfoil
pressure-side metal plate are respectively formed with a
separate metal plate of a metal plate forming the main body
5 of the stationary blade.
[Claim 61
The steam turbine according to claim5, wherein the airfoil
suction-side metal plate and the airfoil pressure-side metal
plate are respectively formed with the separate metal plate
10 of the main body of the stationary blade at a part of a region
on the outer peripheral side in the stationary blade height
direction.
[Claim 71
The steam turbine according to any one of claims 1 to
wherein the airfoil suction-side metal plate is formed
with the same member as the metal plate forming the main body
of the stationary blade, and
wherein the airfoil pressure-side metal plate is formed
20 with a separate metal plate of the metal plate forming the main
body of the stationary blade.
[Claim 81
The steam turbine according to claim 7,
wherein the stationary blade has a reinforcing rib, to
25 reinforce a welded part between the metal plate forming the
b
mainbodyofthe stationarybladeandthe airfoil pressure-side
metal p l a t e , in the blade hollow part, and
whereinthereinforcingribhasaventholetocommunicate
the blade hollow parts divided with the reinforcing r i b into
5 two sections.
[Claim 91
A steam turbine stationary blade having a slit, t o guide
l i q u i d d r o p l e t s depositedon abladewallsurfacetotheinside
of the stationary blade, in the blade wall surface,
10 wherein the stationary blade is formed in a hollow blade
shape by deformation processing a metal p l a t e , and
wherein the s l i t is formed by overlaying an a i r f o i l
suction-side metal plate and an a i r f o i l pressure-side metal
plate with a gap therebetween in a blade t a i l part of the
15 stationary blade.
[Claim 101
The steam turbine stationary blade according t o claim
9, further comprising second slits provided in a p l u r a l i t y of
positions in a blade height direction on the upstream side of
20 the slit in a mainstream flow direction,
wherein the second slits are connected t o the gap provided
between the a i r f o i l suction-side metal plate and the a i r f o i l
pressure-side metal p l a t e .
[Claim 111
The steam turbine stationary blade according t o claim
10,
wherein the s l i t and the second slits are provided on
the pressure side of a i r f o i l , and
wherein the second slit is provided i n a position i n a
5 range of 0.65 t o 0.75 as 1/L r a t i o between a distance 1 along
a blade surface from the a i r f o i l leading edge end of the
s t a t i o n a r y b l a d e t o an a r b i t r a r y p o s i t i o n o f t h e blade surface
andadistanceLalongthebladesurface f r o m t h e a i r f o i l l e a d i n g
edge end t o the t r a i l i n g edge of t h e s t a t i o n a r y blade, and the
10 slit is provided i n a potion i n a range of 0.75 t o 0.9 as the
1 / L r a t i o .
[Claim 121
The steam turbine s t a t i o n a r y blade according t o any one
of claims 9 t o 11, further comprising:
15 a p a i r of piece holes provided i n the a i r f o i l suction-side
metal p l a t e and the a i r f o i l pressure-side metal p l a t e ;
a positioning piece having a spacer, held between the
andthe airfoil pressure-side
metal p l a t e , t o form a gap, and a convex member, provided a t
20 both ends of the spacer and inserted i n the piece holes, t o
f i x mutual positions of the a i r f o i l suction-side metal p l a t e
and the a i r f o i l pressure-side metal p l a t e ; and
a step p a r t , provided on the blade i n n e r surface side
oftheairfoi1suction-sidemeta1plate,overlaidonthetrai1ing
25 edge side end of the a i r f o i l pressure-side metal p l a t e with
*
a gap therebetween, to form the slit.
[Claim 131
The steam turbine stationary blade according to any one
of claims 9to 12, wherein the
5 and the airfoil pressure-side metal plate are respectively
formed with a separate metal plate of a metal plate forming
the main body of the stationary blade.
[Claim 141
The steam turbine stationary blade according to claim
10 13, wherein the airfoil suction-side metal plate and the airfoil
pressure-side metal plate are respectively formed with the
separate metal plate of the main body of the stationary blade
at a part of a region on the outer peripheral side in the stationary
blade height direction.
15 [Claim 151
The steam turbine stationary blade according to any one
of claims 9 to 12,
wherein the airfoil suction-side metal plate is formed
with the same member as the metal plate forming the main body
20 of the stationary blade, and
wherein the airfoil pressure-side metal plate is formed
with a separate metal plate of the metal plate forming the main
body of the stationary blade.
[Claim 161
2 5 The steam turbine stationary blade according to claim
t 15, wherein the stationary blade has a reinforcing rib, to
reinforce a welded part between the metal plate forming the
mainbody ofthe stationarybladeandtheairfoilpressure-side
metal plate, in the blade hollow part, and
w h e r e i n t h e r e i n f o r c i n g r i b h a s a v e n t h o l e t o c o m m u n i c a t e
the blade hollow parts divided with the reinforcing rib into
two sections.
[Claim 171
The steam turbine according to claim 2 or 3, further
10 comprising a rib formed on the blade inner-side surface of the
airfoil suction-side metal plate or the airfoil pressure-side
metal plate,
wherein the airfoil suction-side metal plate and the
airfoil pressure-side metal plate are joined via the rib.
15 [Claim 181
The steam turbine stationary blade according to claim
10or11, furthercomprisingaribformedonthebladeinner-side
surface ofthe or the airfoil
pressure-side metal plate,
2 0 wherein the airfoil suction-side metal plate and the
airfoil pressure-side metal plate are joined via the rib.
[Claim 191
A steam turbine, substantially as herein described with
reference to accompanying drawings and examples.
[Claim 201
Asteamturbinestationaryblade, s u b s t a n t i a l l y a s h e r e i n
describedwithreferencetoaccompanyingdrawingsandexamples.
Dated this 30- day of July 2013
Of Anand and Anand Advocates
Agent for the Applicant