U.S. patent application number 11/612831 was filed with the patent office on 2007-06-28 for sealing device.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. Invention is credited to Satoru Asai, Kenji Kamimura, Hitoshi Sakakida, Takashi Sasaki, Yoichi Tsuda.
Application Number | 20070147990 11/612831 |
Document ID | / |
Family ID | 37781900 |
Filed Date | 2007-06-28 |
United States Patent
Application |
20070147990 |
Kind Code |
A1 |
Kamimura; Kenji ; et
al. |
June 28, 2007 |
SEALING DEVICE
Abstract
A sealing device by which the leakage of fluid is further
reduced by securely maintaining the adhesion between a base
material and an abradable layer and further strengthening the
prevention of fluid leakage is provided. The sealing device
according to the present invention includes seal strips provided to
either one of a rotating portion or a stationary portion forming a
gap therebetween; and a coating layer provided to a base material
of the rotating portion or the stationary portion so that the
coating layer faces the seal strips. The coating layer is composed
of an abradable layer and a bond coat layer.
Inventors: |
Kamimura; Kenji;
(Yokohama-Shi, JP) ; Sasaki; Takashi;
(Yokohama-Shi, JP) ; Sakakida; Hitoshi; (Ohta-Ku,
JP) ; Tsuda; Yoichi; (Bunkyo-Ku, JP) ; Asai;
Satoru; (Chigasaka-Shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
KABUSHIKI KAISHA TOSHIBA
Tokyo
JP
|
Family ID: |
37781900 |
Appl. No.: |
11/612831 |
Filed: |
December 19, 2006 |
Current U.S.
Class: |
415/173.1 |
Current CPC
Class: |
F16J 15/445
20130101 |
Class at
Publication: |
415/173.1 |
International
Class: |
F01D 11/08 20060101
F01D011/08 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 2005 |
JP |
2005-370129 |
Claims
1. A sealing device for preventing fluid from leaking comprising:
seal strips provided to either one of a rotating component or a
stationary component with a gap formed therebetween; and a coating
layer provided to a base material of the rotating component or the
stationary component so that the coating layer faces the seal
strips, wherein the coating layer is composed of an abradable layer
and a bond coat layer.
2. The sealing device according to claim 1, wherein the bond coat
layer is formed by high-velocity oxygen-fuel or plasma spray so as
to have a porosity of 2.0% or less.
3. The sealing device according to claim 1, wherein the bond coat
layer has a linear expansion coefficient which is controlled to an
intermediate value between that of a base material of the
stationary component and that of the abradable layer.
4. The sealing device according to claim 1, wherein the bond coat
layer is formed of one of Ni-based alloy steel, Co-based alloy
steel and a MCrAlY alloy.
5. The sealing device according to claim 1, wherein the abradable
layer is made of a composition containing any one of a NiCrAl alloy
and bentonite (BN), a composition containing a NiCrFeAl alloy and
bentonite (BN), and a composition containing a MCrAlY alloy and
bentonite (BN).
6. The sealing device according to claim 1, wherein the abradable
layer is disposed above the bond coat layer.
7. The sealing device according to claim 1, wherein the sealing
device is applied to a fluid machinery.
8. The sealing device according to claim 7, wherein the fluid
machinery is a steam turbine provided with a turbine rotor to which
buckets are implanted and nozzles vanes, in which the rotating
component is composed of the turbine rotor and the buckets and the
stationary component is a diaphragm inner ring and a diaphragm
outer ring supporting the nozzle vanes.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a sealing device for
significantly reducing leakage of fluid from a gap between a
stationary portion and a rotating portion of, for example, a fluid
machinery such as steam or gas turbine.
[0003] 2. Related Art
[0004] In general, an efficiency of a steam turbine or a gas
turbine used in an electric power plant is affected by an amount of
fluid used for rotating, for example, turbine blades. That is,
performance of the turbine depends on sealing technology for
reducing an amount of fluid leakage from a gap between a stationary
(or fixed) component and a rotating component of the turbine.
[0005] Therefore, sealing technology for controlling the leakage of
the fluid, which does not contribute to generate the power, has
been recognized to be an important technology for improving the
performance of the turbine.
[0006] FIG. 4 shows an exemplary structure of a steam turbine
provided with such a sealing technology that has been recognized as
an important technology for improving an efficiency of a
turbine.
[0007] This steam turbine has a high-pressure turbine 1 and an
intermediate-pressure turbine 2 housed in one turbine casing 3.
Namely, the steam turbine is called a high-intermediate-pressure
turbine 4, and in addition, a low-pressure turbine 5 is axially
connected to this high-intermediate-pressure turbine 4.
[0008] In such a turbine, one turbine rotor 6 arranged around a
center of the turbine casing 3 is commonly used for the
high-pressure turbine 1 and the intermediate-pressure turbine 2 of
the high-intermediate-pressure turbine 4.
[0009] The each of the high-pressure turbine 1 and the
intermediate-pressure turbine 2 are provided with multiple turbine
stages composed of nozzle vanes (stationary blades) engaged with
the turbine casing 3 and buckets (turbine movable blade) implanted
in the turbine rotor 6 respectively. These turbine stages are
arranged along the axial direction of the turbine rotor 6.
[0010] The low-pressure turbine 5 has a low-pressure turbine rotor
7 axially connected to the turbine rotor 6 of the
high-intermediate-pressure turbine 4. The low-pressure turbine 5 is
connected to the high-intermediate-pressure turbine 4 with a
crossover tube 8. The crossover tube 8 is disposed around the
center of a low-pressure turbine casing 13. Thus, the low-pressure
turbine 5 is of the cross-flow type.
[0011] The cross-flow low-pressure turbine 5 is also provided with
multiple turbine stages each composed of nozzle vanes 11
(stationary blades) engaged with an inner casing 9 and buckets 12
implanted in the low-pressure turbine rotor 7, as in the
high-intermediate-pressure turbine 4. These turbine stages are
arranged along the axial direction of the low-pressure turbine
rotor 7 toward both sides of the inner casing 9 so as to have the
crossover tube 8 at the center.
[0012] Further, the low-pressure turbine 5 is provided with a steam
condenser 10 for condensing the spent steam.
[0013] As shown in FIG. 5, the nozzle vanes 11 of each of the
turbine stages are supported by a diaphragm outer ring 14 at tip
end of the vanes 11 and a diaphragm inner ring 15 at the bottom end
of the nozzle vanes 11.
[0014] As shown in FIG. 6, the diaphragm inner ring 15 is provided
with seal strips 16 facing an outer surface of the turbine rotor 6
(low-pressure turbine rotor 7) having protrusions 18 and recesses
19 (so-called a labyrinth seal). Thus, the leakage of steam through
gaps 17 is reduced.
[0015] The diaphragm outer ring 14 is engaged with the turbine
casing 3 (low-pressure turbine casing 13) and extends toward the
buckets 12.
[0016] The bottom portions of the buckets 12 are implanted in a
turbine disk 20 protruding from the turbine rotor 6 (low-pressure
turbine rotor 7). The buckets 12 are provided with shrouds 21 on
the tip portions thereof. The shrouds 21 are provided with seal
strips 16 facing an inner surface of the diaphragm outer ring 14.
Thus, the leakage of steam through gaps 17 is reduced.
[0017] As described above, the conventional steam turbine is
provided with the seal strips 16 in such a manner that the seal
strips 16 are positioned at each gap 17 between the stationary
component and the rotating component, i.e., between the diaphragm
inner ring 15 and an outer surface of the turbine rotor 6
(low-pressure turbine rotor 7) and between the diaphragm outer ring
14 and the shrouds 21 of the buckets 12. Thus, the seal strips 16
prevent the steam from leaking and contribute to generate the
power.
[0018] Further, there have been provided many inventions relating
to technologies providing a sealing device at a gap between a
stationary component and a rotating component such as disclosed,
for example, in Japanese Unexamined Patent Application Publication
Nos. 2001-123803 and 2005-220879.
[0019] The sealing device shown in FIGS. 5 and 6 has been widely
used in fluid machinery such as a steam turbine and a gas turbine.
In such fluid machinery, the stationary component and the rotating
component contact to each other due to vibration in the operation
thereof. That is, the diaphragm inner and outer rings 15 and 14
supporting nozzle vanes 11 as the stationary components and the
turbine rotor 6 (low-pressure turbine rotor 7) and the shrouds 21
of the buckets 12 as the rotating components, are brought into
contact to each other. Consequently, some of the strips 16 are
broken, and thus, there has a limitation to surely prevent the
steam from leakage.
[0020] Under such circumstances, recently, there is provided a
sealing device employing a technology in which a base material for
either one of the rotating component or the stationary component is
covered with an abradable layer with excellent machinability.
[0021] This abradable layer is as if a sponge-like layer containing
a strengthening material such as plastic or graphite dispersed in a
coating material.
[0022] Therefore, with the abradable layer, the seal strips 16 have
not been broken even if the stationary component and the rotating
component are brought into contact with each other due to the
vibration in the operation. However, such an abradable layer causes
a problem in that an adhesive strength to the base material is
significantly decreased.
[0023] In addition, since the sealing device handles fluid having a
temperature about 300.degree. C. or more, it is required to dispose
a bond coat layer having excellent adhesion property between the
base material and the abradable layer. This bond coat layer is,
however, required to have properties such as corrosion resistance
to corrosive materials, oxidation resistance at high temperature
ambient, and steam oxidation resistance.
[0024] Therefore, provision of an improved and novel sealing device
that can maintain a steam-leakage-preventing property for a long
time has been desired, even if the stationary component and the
rotating component are brought into contact with each other.
SUMMARY OF THE INVENTION
[0025] The present invention was conceived in consideration of the
above circumstances, and an object of the present invention is to
provide a sealing device capable of significantly reducing leakage
of fluid by surely maintaining the adhesion property between a base
material and an abradable layer and further maintaining the sealing
of the fluid leakage.
[0026] The above and other objects can be achieved according to the
present invention by providing a sealing device for preventing
fluid from leaking comprising:
[0027] seal strips provided to either one of a rotating component
or a stationary component with a gap formed therebetween; and
[0028] a coating layer provided to a base material of the rotating
componentor the stationary component so that the coating layer
faces the seal strips,
[0029] wherein the coating layer is composed of an abradable layer
and a bond coat layer.
[0030] In a preferred embodiment, the bond coat layer may be formed
by high-velocity oxygen-fuel or plasma spray so as to have a
porosity of 2.0% or less.
[0031] It is desirable that the bond coat layer has a linear
expansion coefficient which is controlled to an intermediate value
between that of a base material of the stationary portion and that
of the abradable layer. The bond coat layer may be formed of one of
Ni-based alloy steel, Co-based alloy steel and a MCrAlY alloy.
[0032] The abradable layer may be made of a composition containing
any one of a NiCrAl alloy and bentonite (BN), a composition
containing a NiCrFeAl alloy and bentonite (BN), and a composition
containing a MCrAlY alloy and bentonite (BN). It is desirable that
the abradable layer is disposed above the bond coat layer.
[0033] The sealing device may preferably be applied to a fluid
machinery, such as a steam turbine provided with a turbine rotor to
which buckets are implanted and nozzle vanes, in which the rotating
component is composed of the turbine rotor and the buckets and the
stationary component is a diaphragm inner ring and a diaphragm
outer ring supporting the nozzle vanes.
[0034] In the sealing device according to the present invention,
the seal strips provided to either one of the rotating component or
the stationary component. The coating layer composed of an
abradable layer and a bond coat layer is disposed on a base
material of the rotating component or the stationary component so
that the coating layer faces the seal strips. Therefore, the seal
strips are not broken even if the rotating component and the
stationary component are brought into contact with each other due
to vibration in the operation. Consequently, the leakage of fluid
can be surely prevented.
[0035] The nature and further characteristic features of the
present invention will be made clearer from the following
descriptions made with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] In the accompanying drawings:
[0037] FIG. 1 is a schematic diagram of a coating layer adhered to
a base material applied to a sealing device according to an
embodiment of the present invention;
[0038] FIG. 2 is a schematic diagram of an example of a sealing
device according to an embodiment of the present invention in which
seal strips are provided to a stationary (or fixed) component and a
coating layer is adhered to the base material of a rotating
component facing the seal strips;
[0039] FIG. 3 is a schematic diagram of an example of a sealing
device according to another embodiment of the present invention in
which seal strips are provided to a rotating component and a
coating layer is adhered to the base material of a stationary
component facing the seal strips;
[0040] FIG. 4 is a schematic diagram showing a general structure of
a known steam turbine;
[0041] FIG. 5 is a perspective view of one half of a nozzle
diaphragm constituting a stationary component applied to the known
steam turbine; and
[0042] FIG. 6 is a partial cross-sectional view of the known steam
turbine in which the stationary component and the rotating
component are provided with a sealing device.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0043] Embodiments of sealing devices according to the present
invention will be described hereunder with reference to the
accompanying drawings.
[0044] First, with reference to FIG. 1 representing a sealing
device according to an embodiment of the present invention, the
sealing device is applied to a fluid machinery having a rotating
component 31 such as a turbine rotor and buckets and a stationary
(or fixed) component 30 such as a diaphragm inner ring and a
diaphragm outer ring supporting nozzle vanes. A coating layer 33 is
formed on a base material 32 of either one of the rotating
component 31 or the stationary component 30. The coating layer 33
is composed of an abradable layer (upper layer) 35 and a bond coat
layer (lower layer) 36 serving as an adhesive (bonding agent).
[0045] Specifically, as shown in FIG. 2, a shroud of a bucket is an
example of the rotating component 31 and is provided with seal
strips 34. A diaphragm outer ring facing the seal strips 34 is an
example of the stationary component 30. A coating layer 33 is
disposed on the base material 32 of the diaphragm outer ring as the
stationary component 30.
[0046] In another embodiment, as shown in FIG. 3, a diaphragm inner
ring supporting nozzle vanes is an example of the stationary
component 30 and is provided with seal strips 34. A turbine rotor
(low-pressure turbine rotor) facing the seal strips 34 is an
example of the rotating component 31. A coating layer 33 is
disposed on the base material 32 of the turbine rotor (low-pressure
turbine rotor).
[0047] The base material 32 of the rotating component 31 or the
stationary component 30 is an iron-based alloy with a martensite or
bainite microstructure.
[0048] The abradable layer 35 serving as the upper layer of the
coating layer 33 is made of a composition with excellent
machinability. An example of such composition includes a
composition containing a NiCrAl alloy and bentonite (BN), a
composition containing a NiCrFeAl alloy and bentonite (BN), and a
composition containing a MCrAlY alloy and bentonite (BN), or
like.
[0049] The bond coat layer 36 serving as the lower layer of the
coating layer 33 is made of Ni-based alloy steel or pure nickel. An
example of the Ni-based alloy steel includes a NiCr alloy such as
Inconel 625, a NiAl alloy containing 5 wt % of Al in Ni, a Co-based
alloy such as CoNiCrAlY, NiMo alloy steel, and Hastelloy C.
[0050] The bond coat layer 36 is formed by high-velocity
oxygen-fuel (HVOF) or high power plasma spraying so as to have a
porosity of 2.0% or less in order to further enhance the corrosion
resistance, oxidation resistance, and steam oxidation
resistance.
[0051] A bond coat layer 36 formed by high-velocity oxygen-fuel
(HVOF) or high power plasma spray in order to enhance the
resistance such as corrosion resistance is controlled so as to have
a linear expansion coefficient of an intermediate value between
that of the base material 32 and that of the abradable layer 35.
Thus, the resistance to heat stress caused by the operation can be
improved.
[0052] For example, in a known steam turbine in which the seal
strips 34 are disposed between the rotating component 31 and the
stationary component 30, the distance (clearance) therebetween is
0.5 to 0.7 mm, and if the rotating component 31 and the stationary
component 30 are brought into contact with each other, the seal
strips 34 are liable to be broken. Therefore, the fluid leakage
cannot be sufficiently prevented.
[0053] In addition, in the known steam turbine, an iron-based alloy
with a martensite or bainite microstructure was used as the base
material of the rotating component 31 and the stationary component
30. Therefore, the base material could not often maintain the
corrosion resistance, oxidation resistance, and steam oxidation
resistance over a long term operation, thus having been
disadvantageous.
[0054] However, in the sealing device according to the present
invention, the coating layer 33 composed of the abradable layer 35
and the bond coat layer 36 is adhered to a base material 32. The
abradable layer 35 is made of a material with excellent
machinability, such as a NiCrAl alloy. The bond coat layer 36 is
made of a material with excellent corrosion resistance, oxidation
resistance, and steam oxidation resistance, such as a NiAl alloy.
The bond coat layer 36 is formed by high-velocity oxygen-fuel
(HVOF) or high power plasma spraying so as to have a porosity of
2.0% or less. As a result, the distance between the adjacent seal
strips 34 can be decreased to 0.2 mm.
[0055] It was confirmed through experiment that when the distance
was 0.2 mm, the seal strips 34 were not broken even if the rotating
component 31 and the stationary component 30 were brought into
contact with each other. Thus, a sealing device excellent in
performance can be realized.
* * * * *