U.S. patent application number 13/742824 was filed with the patent office on 2013-07-25 for steam turbine and blade for steam turbine.
This patent application is currently assigned to Kabushiki Kaisha Toshiba. The applicant listed for this patent is Kabushiki Kaisha Toshiba. Invention is credited to Yoshifumi Iwasaki, Hiroshi Kawakami, Sakae Kawasaki, Shinichiro Ohashi, Naoki Shibukawa, Tomohiko TSUKUDA.
Application Number | 20130189077 13/742824 |
Document ID | / |
Family ID | 47563264 |
Filed Date | 2013-07-25 |
United States Patent
Application |
20130189077 |
Kind Code |
A1 |
TSUKUDA; Tomohiko ; et
al. |
July 25, 2013 |
STEAM TURBINE AND BLADE FOR STEAM TURBINE
Abstract
A steam turbine includes: a turbine rotor shaft; a plurality of
blades that are provided on the turbine rotor shaft and are rotated
by a steam flow; tip covers that are attached to tip ends of the
respective blades and are connected to and in contact with one
another; at least one water drip fin that is provided along a
circumferential direction at the tip cover, and outwardly extends
in a radial direction of each of the blades; and a diaphragm outer
ring that is disposed at an outer circumferential side from each of
the blades, and has a drain catcher opposed to a tip end portion of
the water drip fin, wherein the tip cover is provided with a
leading edge that is formed at a downstream side in an axial
direction from a leading edge of the blade or at a position in the
axial direction corresponding to the leading edge of the blade in
the axial direction.
Inventors: |
TSUKUDA; Tomohiko;
(Kawasaki-Shi, JP) ; Kawakami; Hiroshi;
(Yokohama-Shi, JP) ; Kawasaki; Sakae;
(Yokohama-Shi, JP) ; Shibukawa; Naoki;
(Saitama-Shi, JP) ; Ohashi; Shinichiro; (Ota-Ku,
JP) ; Iwasaki; Yoshifumi; (Yokohama-Shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kabushiki Kaisha Toshiba; |
Tokyo |
|
JP |
|
|
Assignee: |
Kabushiki Kaisha Toshiba
Tokyo
JP
|
Family ID: |
47563264 |
Appl. No.: |
13/742824 |
Filed: |
January 16, 2013 |
Current U.S.
Class: |
415/92 ;
416/223R |
Current CPC
Class: |
F01D 5/225 20130101;
F01D 25/32 20130101; F01D 5/14 20130101; F05B 2260/602 20130101;
F01D 5/147 20130101; F01D 11/08 20130101 |
Class at
Publication: |
415/92 ;
416/223.R |
International
Class: |
F01D 5/14 20060101
F01D005/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 19, 2012 |
JP |
2012-008849 |
Claims
1. A steam turbine, comprising: a turbine rotor shaft; a plurality
of blades that are provided on the turbine rotor shaft and are
rotated by a steam flow; tip covers that are attached to tip ends
of the respective blades and are connected to and in contact with
one another; at least one water drip fin that is provided along a
circumferential direction at the tip cover, and outwardly extends
in a radial direction of each of the blades; and a diaphragm outer
ring that is disposed at an outer circumferential side from each of
the blades, and has a drain catcher opposed to a tip end portion of
the water drip fin, wherein the tip cover is provided with a
leading edge that is formed at a downstream side in an axial
direction from a leading edge of the blade or at a position in the
axial direction corresponding to the leading edge of the blade in
the axial direction.
2. The steam turbine according to claim 1, wherein the water drip
fin is provided along the leading edge of the tip cover.
3. The steam turbine according to claim 1, wherein a tip end
position of the water drip fin has an outside diameter smaller than
a maximum outside diameter of the tip cover.
4. The steam turbine according to claim 1, wherein a plurality of
the water drip fins are provided at the tip cover along the
circumferential direction.
5. The steam turbine according to claim 1, wherein each of the
blades has a water droplet guide groove that extends in the radial
direction of the blade, with one end portion reaching the tip end
of the blade, at an upstream side from the leading edge of the tip
cover in a side surface at a back side.
6. The steam turbine according to claim 1, wherein the drain
catcher has an opening portion with a maximum differential
expansion being within a width in the axial direction of an opening
even when the maximum differential expansion occurs at a position
in the axial direction of the tip end of the water drip fin at a
time of a steady state operation.
7. A blade of a steam turbine, comprising: blades rotated by a
steam flow; tip covers that are attached to tip ends of the blades
and are connected to and in contact with one another; and at least
one water drip fin that is provided along a circumferential
direction at the tip cover, and outwardly extends in a radial
direction of each of the blades, wherein the tip cover is provided
with a leading edge that is formed at a downstream side in an axial
direction from a leading edge of the blade or at a position in the
axial direction corresponding to the leading edge of the blade in
the axial direction.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from Japanese Patient application No. 2012-008849, filed
on Jan. 19, 2012, the entire contents of each of which are
incorporated herein by reference.
FIELD
[0002] Embodiments described herein relates to a steam turbine and
a blade of the steam turbine.
BACKGROUND
[0003] In the turbine low pressure section of a nuclear power
turbine, a geothermal turbine or a thermal power turbine, the
temperature of turbine driving steam becomes comparatively low. A
part of the turbine driving steam condenses during expansion, and
becomes water to flow to the inner and outer circumferential walls
of the steam passage and the turbine blades.
[0004] The water that flows on the inner and outer circumferential
walls of the steam passage and the turbine blades eventually grows
to be water droplets with relatively large particle sizes. The
water droplets become the factors that erode the leading edges of
the turbine blades, generate a collision resistance to the rotation
of the turbine blades, and reduce the blade efficiency of the
turbine blades.
[0005] As described above, the presence of the water in the turbine
adversely affects the turbine efficiency and reliability. In
contrast, there has been conventionally known a steam turbine that
has the structure for removing adhering water. Specifically, the
steam turbine has a seal fin which is provided at the tip end
portion of each of the turbine blades, and a space portion provided
for the purpose of capturing water, at the tip end side of the seal
fin. The water that flows inside the steam turbine is scattered in
the outer circumferential direction by the centrifugal force by
hitting against the seal fins, and is captured by the space portion
(see Japanese Patent Laid-Open No. 2005-2917).
[0006] The conventional steam turbine captures the water in the
steam turbine by the seal fins provided at the turbine blade tip
end portions. However, the conventional steam turbine has been
provided with seal fins which are originally intended for
prevention of steam leakage, and therefore, collection of water is
not necessarily be sufficient. Specifically, due to the effect of
the steam flow in the steam turbine and the centrifugal force, the
water cannot be favorably guided to the space portion, even though
the seal fines are used.
[0007] As a result, the conventional steam turbine has the problem
of being unable to suppress erosion by the drain which occurs to
the steam turbine and reduction of the rotational resistance of the
turbine blades.
[0008] Embodiments described herein is made in view of the
circumstances as described above, and has an object to provide a
steam turbine and a blade of the steam turbine that can favorably
collect water generated in the steam turbine, and prevent reduction
in turbine efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a configuration diagram showing one embodiment of
a steam turbine according to the present invention;
[0010] FIG. 2 is a plan view showing blades of the steam turbine of
FIG. 1 from an outer circumferential side;
[0011] FIG. 3 is a configuration diagram for explaining a
positional relation in an axial direction, of a water drip fin and
an opening portion of a drain catcher;
[0012] FIG. 4 is an explanatory view of a flow of steam in the
steam turbine;
[0013] FIG. 5 is a configuration diagram showing a steam turbine as
a first modified example in which a water droplet guide groove is
formed;
[0014] FIG. 6 is a plan view of blades of the steam turbine of FIG.
5 from an outer circumferential side;
[0015] FIG. 7 is a configuration diagram showing a steam turbine as
a second modified example in which a plurality of water drip fins
are provided;
[0016] FIG. 8 is a plan view showing blades of the steam turbine of
FIG. 7 from an outer circumferential side; and
[0017] FIG. 9 is a configuration diagram showing a steam turbine as
a third modified example in which water drip fins are
discontinuously disposed.
DETAILED DESCRIPTION
[0018] An embodiment of a steam turbine and a blade of the steam
turbine according to the present invention will be described based
on the accompanying drawings. The steam turbine and the blade of
the steam turbine in the present embodiment are applied to, for
example, a low pressure section of a turbine.
[0019] FIG. 1 is a configuration diagram showing one embodiment of
the steam turbine according to the present invention.
[0020] The steam turbine 1 includes a turbine rotor shaft 3, a
plurality of blades 2 that are provided on the turbine rotor shaft
3 and are rotated by a steam flow, tip covers 20 that are attached
to tip ends of the respective blades 2 and are connected to and in
contact with one another, at least one water drip fin 30 that is
provided along a circumferential direction of the tip cover 20 and
outwardly extends in a radial direction of each of the blades 2,
and a diaphragm outer ring 40 that is disposed at an outer
circumferential side from each of the blades 2 and has a drain
catcher 43 which is opposed to a tip end portion of the water drip
fin 30.
[0021] FIG. 2 is a plan view showing blades 2 of a steam turbine 1
of FIG. 1 from an outer circumferential side.
[0022] The tip cover 20 is provided with a leading edge 25 that is
formed at a downstream side in the axial direction from the leading
edge 12 of the blade 2 or a position in the axial direction
corresponding to the leading edge 12 of the blade 2 in the axial
direction.
[0023] Illustration in FIGS. 1 and 2 is on the precondition that
the steam flows from the left to the right. In the blade 2, the
description is made with the left side as a front, and the right
side as a rear. In the steam turbine 1, a flowing direction of the
steam corresponds to a direction of the turbine rotor shaft 3, and
therefore, the flowing direction of the steam is defined as the
axial direction.
[0024] As shown in FIG. 1, the steam turbine 1 mainly has the
turbine rotor shaft 3, the blades 2 and vanes 4.
[0025] The blades 2 are disposed at a downstream side of the vanes
4 to be opposed to the vanes 4, and form a row of blades in a
circumferential direction of the turbine rotor shaft 3. The blade 2
has a tip cover 20 formed integrally with the blade 2 at a blade
tip end.
[0026] As shown in FIG. 2, the tip cover (cover) 20 is formed by a
back side cover 21 that extends in a circumferential direction of a
back side of the blade 2, and a front side cover 22 that extends in
a circumferential direction of a front side of the blade 2. The
adjacent covers 20 are in contact with each other. A position in
the axial direction of a cover leading edge 25 of the front side
cover 22 is at a rear side in the axial direction (downstream side
in the axial direction) from a blade effective portion leading edge
12 of the blade 2, or corresponds to the blade effective portion
leading edge 12 in the axial direction. When untwist (torsional
moment which occurs in a direction opposite to the torsion of the
blade) occurs to the cover 20 due to the centrifugal force of the
blade 2, the back side cover 21 and the front side cover 22 of the
adjacent blades 2 are in contact with each other on a cover contact
surface 23. Thereby, the steam turbine 1 obtains a vibration
damping effect of a group of the blades 2 on an entire
circumference.
[0027] The cover 20 has a tip water drip fin 30 which is formed
integrally with the cover 20, on a cover outer circumferential
surface 27. The tip water drip fin (water drip fin) 30 is a fin
outwardly extending in the radial direction of the blade 2 along
the cover leading edge 25, and is provided in a ring shape
throughout an entire circumference of the cover 20. Note that the
water drip fin 30 may be provided at a rear side from the cover
leading edge 25.
[0028] As shown in FIG. 1, an outside diameter .PHI.B at a tip end
position of the water drip fin 30 is smaller than a maximum outside
diameter .PHI.A of the cover 20. The cover 20 has an inclination
slanting downward to the front, and has an outside diameter which
is larger at a cover trailing edge 26 side and smaller at a cover
leading edge 25 side, and a length in the radial direction of the
water drip fin 30 is determined so that the outside diameter .PHI.B
does not become larger than the cover trailing edge 26.
[0029] The vane 4 is provided between the nozzle diaphragm outer
ring 40 and a nozzle diaphragm inner ring 45 which is located in an
inner side in a radial direction of the nozzle diaphragm outer ring
40. The nozzle diaphragm outer ring (diaphragm outer ring) 40 has a
nozzle strip 60 and the drain catcher 43.
[0030] The nozzle strip 60 is provided at the diaphragm outer ring
40 that is opposed to the rear side of the blade 2. The nozzle
strip 60 functions as resistance of a watercourse of a space
between the cover 20 and the diaphragm outer ring 40, and reduces a
tip side leakage steam flow amount.
[0031] The drain catcher 43 is a space for collecting water
droplets removed from the water drip fin 30. The drain catcher 43
has an opening portion 46 at a position in the axial direction that
is opposed to the tip end of the water drip fin 30.
[0032] Here, FIG. 3 is a configuration diagram for explaining a
positional relation in the axial direction of the water drip fin 30
and the opening portion 46 of the drain catcher 43.
[0033] In general, a differential expansion in the axial direction
of the low pressure turbine is approximately 20 mm at the maximum.
For the water drip fin 30, a size of the opening portion 46 of the
drain catcher 43 (position in the axial direction of the water drip
fin 30 with respect to the opening portion 46) is determined with
the differential expansion taken into consideration.
[0034] Specifically, as shown in FIG. 3, even when the maximum
differential expansion occurs in the longitudinal direction to the
water drip fin 30 (turbine rotor shaft 3) at a time of a steady
state operation, the maximum differential expansion at the tip end
of the water drip fin 30 is configured to be within a width in the
axial direction of the opening portion 46 of the drain catcher
43.
[0035] An opening portion inlet side 47 of the drain catcher 43
expands in the shape of a trumpet in sectional view, and a position
in the axial direction of the opening portion inlet side 47 is from
a front side axial position X1 to a rear side axial position X2
(positions X1 and X2 are the positions where the trumpet-shaped
opening starts to close) of FIG. 3. The tip end of the water drip
fin 30 is within the range in the axial direction of the opening
portion inlet side 47 at a time of stoppage and at a time of the
steady state operation when the maximum differential expansion can
occur.
[0036] Next, an operation of the steam turbine 1 and the blade 2
will be described.
[0037] FIG. 4 is an explanatory view of a flow of the steam in the
steam turbine 1.
[0038] During operation of the steam turbine 1, a part of the
driving steam condenses, and becomes liquid films L to adhere to
the vanes 4. When the liquid film L reaches a vane trailing edge 5
of the vane 4, the liquid film L becomes a water droplet D and
scatters from the vane trailing edge 5 as the arrow A in the
drawing. At this time, energy of the steam is used for acceleration
of the water droplet D, and the energy of the steam is
consumed.
[0039] The water droplet D cannot completely ride on the flow of
the steam due to inertia, and collides with and adheres to the
blade effective portion leading edge 12 of the rotating blade 2.
Collision of the water droplet D becomes a braking force to the
rotation of the blade 2, and reduces the turbine efficiency.
Further, collision of the water droplet D becomes the factor that
causes erosion of the blade effective portion leading edge 12 of
the blade 2 due to an impact thereof.
[0040] As shown in FIG. 1, the water droplet D moves outwardly on a
blade surface of the blade 2 in the radial direction by the
centrifugal force, and reaches a tip end in the radial direction of
a blade effective portion side surface 11. Among the water droplets
D which reach the tip end in the radial direction of the blade
effective portion side surface 11, the water droplet D, which is
present at a front side from the cover end surface 24 of the cover
leading edge 25, rides onto a blade effective portion outer
circumferential surface 13 by the surface tension at a boundary
between the blade effective portion side surface 11 and the blade
effective portion outer circumferential surface 13.
[0041] The water droplet D on the blade effective portion outer
circumferential surface 13 moves rearward by the steam force, and
reaches the water drip fin 30. The water droplet D which reaches
the water drip fin 30 moves to the tip end of the water drip fin 30
by the centrifugal force, is blown off to the outer circumferential
side of the blade 2 from the tip end, and is captured by the drain
catcher 43.
[0042] Further, it is known that distribution of the amount of
water adhering to the vane 4 (diaphragm outer ring 40) is larger at
the outer circumferential side and that a large amount of water is
also present on an inner circumferential wall surface 42 of the
diaphragm outer ring 40. Further, the water droplet D which is
scattered from the vane 4 is deflected to the outer circumferential
side by the centrifugal force due to a velocity component in the
circumferential direction of itself. Therefore, some of the water
droplets D which are scattered from the vane 4 and the inner
circumferential wall surface 42 directly adhere to the cover end
surface 24 of the cover leading edge 25, the cover outer
circumferential surface 27 or the fin end surface 31 at the front
side of the tip water drip fin 30, and are captured by the drain
catcher 43 as described above.
[0043] The steam turbine 1 and the blade 2 in the present
embodiment can effectively remove and collect the water droplets D
adhering to the blade 2. Thereby, the steam turbine 1 and the blade
2 can prevent erosion by the water droplets D. Further, the steam
turbine 1 and the blade 2 can suppress the rotational resistance of
the blade 2 by the water droplets D, and can prevent reduction of
the turbine efficiency.
[0044] In particular, the blade 2 is provided with the cover that
has the cover leading edge 25 which corresponds to the rear side
from the blade effective portion leading edge 12 of the blade 2 or
the blade effective portion leading edge 12, and therefore, the
water droplets D which adhere to the blade effective portion side
surface 11 and further reaches the blade effective portion outer
circumferential surface 13 can be efficiently removed.
[0045] Further, the water drip fin 30 is provided not for the
purpose of sealing leaking steam but for capturing the water
droplets D in the drain catcher 43, therefore the outside diameter
.PHI.B at the tip end position of the water drip fin 30 can be made
smaller than the maximum outside diameter .PHI.A of the tip cover
20. Therefore, the risk of the tip end of the water drip fin 30
interfering with the inner circumferential surface of the diaphragm
outer ring 40 or the nozzle strip 60 can be avoided, at a time of
assembly and at a time of operation of the steam turbine 1.
[0046] Note that the steam turbine 1 and the blade 2 in the present
embodiment may be configured as a modified example described as
follows.
[0047] FIG. 5 is a configuration diagram showing the steam turbine
1 as the first modified example in which a water droplet guide
groove 15 is formed.
[0048] FIG. 6 is a plan view showing the blades 2 of the steam
turbine 1 of FIG. 5 from an outer circumferential side.
[0049] The blade 2 has one water droplet guide groove 15 or more
(two in FIGS. 5 and 6) at a front side (blade effective portion
leading edge 12 side) from the cover leading edge 25 in a
blade-back-side side surface 14. The water droplet guide groove 15
extends in the radial direction of the blade 2 and one end portion
reaches the tip end of the blade 2.
[0050] When the water droplet D adhering to the blade-back-side
side surface 14 moves in the outer circumferential direction of the
blade 2, the blade 2 moves the water droplet D to the blade
effective portion outer circumferential surface 13 by the water
droplet guide groove 15. Thereby, the steam turbine 1 and the blade
2 can remove the water which adheres to the blade-back-side side
surface 14 more reliably.
[0051] FIG. 7 is a configuration diagram showing the steam turbine
1 as a second modified example in which a plurality of water drip
fins 30 are provided.
[0052] FIG. 8 is a plan view showing the blades 2 of the steam
turbine 1 of FIG. 7 from an outer circumferential side.
[0053] The cover 20 has a plurality (two in FIGS. 7 and 8) of water
drip fins 30 arranged in the axial direction. By providing a
plurality of water drip fins 30, the water droplets D which reach
the cover outer circumferential surface 27 can be reliably captured
in the drain catcher 43.
[0054] FIG. 9 is a configuration diagram showing the steam turbine
1 as a third modified example in which the water drip fins 30 are
discontinuously disposed.
[0055] The water drip fins 30 outwardly extend in the radial
direction of the blades 2 along the cover leading edges 25, and are
discontinuously provided in the circumferential direction of the
covers 20. The water drip fin 30 is provided with the objective of
mainly removing the water from the blade effective portion outer
circumferential surface 13. Therefore, when the trajectory of the
water droplet D from the blade effective portion outer
circumferential surface 13 is properly predicted, the water drip
fin 30 can be discontinuously disposed to correspond to the
trajectory of the water droplet D.
[0056] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
embodiments described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing from the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
inventions.
[0057] For example, the outside diameter .PHI.B at the tip end
position of the water drip fin 30 may be larger than the maximum
outside diameter .PHI.A of the cover 20. In this case, a distance
between the opening portion inlet side 47 (see FIG. 3) of the drain
catcher 43 and the tip end of the water drip fin 30 becomes small,
which is effective in that the water droplet D can be reliably
guided to the drain catcher 43.
[0058] Further, in place of the nozzle strip 60 of the diaphragm
outer ring 40, a tip seal fin that is provided in a ring shape
throughout the entire circumference may be provided integrally with
the cover outer circumferential surface 27 of the tip cover 20.
* * * * *