US20100054924A1

US20100054924A1 - Brush seal and turbine using the same

Info

Publication number: US20100054924A1
Application number: US12/230,796
Authority: US
Inventors: Noriyoshi Uyama; Naoki Hagi; Takeaki Oya
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 2008-09-04
Filing date: 2008-09-04
Publication date: 2010-03-04

Abstract

A brush seal in which an increase in steady-state wear is prevented and the influence of turbulence is eliminated is provided. The invention includes a brush seal including brush seal bristles formed of a plurality of wires and mounted to a seal box in such a manner that one end thereof is in contact with a downstream cylindrical portion; and a downstream support plate mounted next to the brush seal bristles in a direction in which combustion gas flows, for restricting the motion of the brush seal bristles. The brush seal seals the combustion gas flowing between the seal box and the downstream cylindrical portion. The brush seal includes restraint bristles mounted opposite to the downstream support plate and next to the brush seal bristles in the direction in which the combustion gas flows. The restraint bristles have a degree of elasticity such that the downstream cylindrical portion is not damaged even if coming into contact with the downstream cylindrical portion and such that the contact deformation of the brush seal bristles is not hindered.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a brush seal and a turbine using the same.
This application is based on Japanese Patent Application, Publication No. 2008-121512, the content of which is incorporated herein by reference.
2. Description of Related Art
Gas turbines and steam turbines have, for example, a sealing mechanism, around their rotation shafts, for preventing gas from leaking from a high pressure side to a low pressure side.
One common example of this sealing mechanism is a labyrinth seal, which is a non-contact seal.
The labyrinth seal has a limitation in reducing the amount of leakage, that is, in improving sealing performance, because it is a non-contact seal. Therefore, brush seals are starting to be used to improve the sealing performance.
Brush seals have a plurality of bristles formed in a ring shape (brush seal bristles) to achieve sealing in such a manner that the ends of the brush seal bristles are in contact with a rotating part.
The rotating part, for example, the rotor of a gas turbine is deformed by a centrifugal force and heat caused by the operation thereof, while on the other hand, a stator housing is also expanded by the heat, causing a change in the distance between the brush seal and the rotor.
Although this change is absorbed by the deflection of the bristles, a deflection towards the downstream side may deteriorate its sealing performance. Therefore, a back plate is provided downstream of the brush seal bristles to prevent deflection towards the downstream side.
For the deflection of the bristles, a space is provided upstream of the bristles.
Since brush seals are contact seals, the ends of the bristles that are in contact with the rotating part are worn down with time.
In addition to this wear over time, if the fluid passing through the brush seal bristles becomes turbulent, this will cause the bristles to flutter (which is significant, in particular, at the upstream side), thus breaking the bristles.
This breakage of the bristles causes the broken portion to be out of contact with the rotor, thus deteriorating the sealing performance of the brush seal.
The deterioration of the sealing performance of the brush seal is problematic because, for example, it decreases the output of the turbine.
Another problem is that the frequency of replacement of the brush seal must be increased in order to prevent a decrease in output, thus increasing maintenance costs.
One example of a solution to such problems is proposed in Japanese Unexamined Patent Application, Publication No. 2001-73708.
It involves limiting the deflection of brush seal bristles by providing a brake plate also upstream of the brush seal bristles and reducing the occurrence of turbulence by providing a through hole in the brake plate, thereby preventing, particularly, upstream bristles from fluttering.
However, the solution described in Japanese Unexamined Patent Application, Publication No. 2001-73708 strongly restricts motion of the brush seal bristles to the vicinity of the rotor by using the downstream back plate and the upstream brake plate, so that the available length for deflection of the brush seal bristles is short.
This increases the rigidity of the brush seal bristles, which increases a contact pressure on the rotor, thus posing the problem of increasing the wear of the bristles and the rotor in a steady state.
Therefore, this approach does not yet sufficiently maintain the sealing performance of the brush seal.
Moreover, since the back plate and the brake plate are rigid, they may damage the rotor when coming into contact with the rotor.

BRIEF SUMMARY OF THE INVENTION

In view of the above problems, an object of the present invention is to provide a brush seal in which an increase in steady-state wear is prevented and the influence of turbulence is eliminated and a turbine using the same.
To solve the above problems, the present invention adopts the following solutions.
A brush seal according to a first aspect of the present invention includes a bristle section formed of a plurality of bristles and mounted to a stationary section in such a manner that one end thereof is in contact with a rotating section; and a brake section mounted next to the bristle section in a direction in which fluid flows, for restricting the motion of the bristle section, the brush seal sealing the fluid flowing between the stationary section and the rotating section, wherein the brush seal includes a restraint section mounted opposite to the brake section and next to the bristle section in the direction in which the fluid flows, the restraint section having a degree of elasticity such that the rotating section is not damaged even if coming into contact with the rotating section and such that the contact deformation of the bristle section is not hindered.
The brush seal according to the first aspect of the present invention is configured such that, when the distance between the stationary section and the rotating section changes, the change is absorbed by the deflection of the bristle section. The bristle section is limited in motion by the brake section mounted next thereto in the fluid flowing direction, so that it deflects toward the restraint section.
Since the restraint section has a degree of elasticity such that the contact deformation of the bristle section is not hindered, the restraint section can be elastically deformed to absorb the deflection of the bristle section.
When the restraint section can absorb the deflection of the bristle section, the contact frictional force of the bristle section is not increased with changes in the distance between the stationary section and the rotating section, which prevents an increase in steady-state wear.
When turbulence occurs in fluid to cause parts of the bristles to flutter, the motion of the bristles is restricted by the restraint section because the force of the parts of the bristles that acts on the restraint section is much smaller than the force of the bristle section, that is, the whole of the bristles.
Thus, the motion of parts of the bristles due to the turbulence is prevented, which prevents fluttering, thereby preventing breakage of the bristles caused by the fluttering.
This prevents deterioration of the sealing performance of the brush seal, thereby preventing, for example, a decrease in the output of the turbine and reducing the frequency of replacement of the brush seal so that maintenance costs are decreased.
Moreover, since the restraint section has a degree of elasticity such that the rotating section is not damaged even if coming into contact with the rotating section, there is no possibility of damaging the rotating section even if the restraint section comes into contact with the rotating section.
If the restraint section comes into contact with the rotating section, the rotating section is worn down and may be damaged. Therefore, it is preferable that the end position of the restraint section be farther away from the rotating section than the end of the bristle section.
In the first aspect of the present invention, it is preferable that the restraint section be disposed upstream of the bristle section in the direction in which the fluid flows.
With this structure, the brake section is disposed at the downstream side, which prevents the bristle section from deflecting toward the downstream side, thereby preventing a decrease in sealing performance.
In the brush seal according to the first aspect, it is preferable that the restraint section be a bundle of bristles formed of a plurality of bristles whose end is farther away from the rotating section than the end of the bristles.
In this structure, the bristle bundle is formed of a plurality of bristles. Therefore, the elasticity of the restraint section in the axial direction and the radial direction can easily be set to a specified value by appropriately adjusting the elasticity of the bristles and the space among the bristles.
A turbine according to a second aspect of the present invention uses the brush seal according to the first aspect.
The turbine according to the second aspect of the present invention uses a brush seal in which an increase in steady-state wear is prevented and the influence of turbulence is eliminated. This prevents the deterioration of the sealing performance of the brush seal and a decrease in the output of the turbine.
This also decreases the frequency of replacement of the brush seal so that maintenance costs are reduced.
In the present invention, the restraint section has a degree of elasticity such that the contact deformation of the bristle section is not hindered. This prevents an increase in contact frictional force with changes in the distance between the stationary section and the rotating section, thereby preventing an increase in steady-state wear.
Moreover, the motion of the bristles due to the turbulence of fluid is restrained by the restraint section. This prevents breakage of the bristles due to the turbulence.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view showing part of a gas turbine incorporating an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a downstream brush seal according to an embodiment of the present invention.

FIG. 3 is a front view of the downstream brush seal according to the embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 to 3, an embodiment of the present invention will be described.
FIG. 1 is a fragmentary longitudinal sectional view showing the schematic structure of an inlet of a gas turbine 1 equipped with a brush seal according to this embodiment.
The gas turbine 1 has, in its interior, a plurality of moving blades 3 mounted to a rotor (not shown) and a plurality of stationary blades 5 provided at the stator side around the rotor, which are arranged alternately along the axis of the rotor (in the lateral direction in FIG. 1), to form a combustion gas passage 7 therethrough. Individual adjacent stationary blades 5 and moving blades 3 form a plurality of stages, which are arranged along the axis of the rotor (in the lateral direction in FIG. 1)
A multistage structure is formed of continuous stages, that is, first, second, third, and fourth stages, and so on, counting from the upstream side where combustion gas flows in.
FIG. 1 shows blades from a first-row moving blade 3 a to a second-row moving blade 3 b.
In FIG. 1, suffixes “a” and “b” added to the reference numerals are used for distinguishing between the first row and the second row; a indicates a part or a component of the first row and b indicates a part or a component of the second row. In the following specification, when the first and second rows are to be distinguished, a and b are added, whereas when no particular distinction is needed, parts or components are denoted only by reference numerals without adding a or b.
The combustion gas supplied into the gas turbine 1 rotates the moving blades 3 when flowing in the combustion gas passage 7 in a flowing direction 9 to apply a rotating force to the rotor. This rotating force rotates, for example, a generator (not shown) connected to the rotor, to generate power.
The plurality of moving blades 3 are arranged radially and are firmly mounted to the outer circumference of a disk (a rotating section) 11 which protrudes from the periphery of the rotor (not shown) in a cylindrical shape.
A large number of the stationary blades 5 are arranged radially and are retained by a ring-shaped outer partition ring 15 and a ring-shaped inner partition ring (a stationary section) 17 which are firmly fixed to a turbine blade ring 13.
A sealing structure 19 for preventing leakage of combustion gas is provided between the inner partition ring 17 and the disk 11.
The end of the inner partition ring 17 adjacent to the rotor has a seal box 21 that constitutes the sealing structure 19.
The end of a disk 11 a downstream in the flowing direction 9 has a double cylindrical portion that gradually decreases in diameter in the downstream direction, that is, an upstream cylindrical portion 23 and a downstream cylindrical portion 25.
The surface of the seal box 21 opposite the upstream cylindrical portion 23 has an upstream brush seal (a brush seal) 27, and the surface opposite the downstream cylindrical portion 25 has a downstream brush seal (a brush seal) 29.
The upstream end of a disk 11 b of the second row has a cylindrical portion 31 which has substantially the same diameter as the downstream cylindrical portion 25.
A labyrinth seal 33 is disposed between the cylindrical portion 31 and the seal box 21.
A seal 35 is mounted between the downstream cylindrical portion 25 and the cylindrical portion 31.
The upstream brush seal 27 and the downstream brush seal 29 have substantially the same structure, but different sizes. Accordingly, a description of the downstream brush seal 29 will be given and a duplicated description of the upstream brush seal 27 will be omitted hereinafter. Like or corresponding parts are given the same names, and the upstream brush seal 27 and the downstream brush seal 29 are not distinguished from each other in the following description.
FIG. 2 is an enlarged longitudinal sectional view of the downstream brush seal 29 in FIG. 1. FIG. 3 is a front view of the downstream brush seal 29.
The downstream brush seal 29 is mounted in a ring-shaped installation space 22 provided under the lower surface of the seal box 21.
The downstream brush seal 29 is a ring-shaped component, which is circumferentially divided into a plurality (for example, six) of brush seal segments 37, as shown in FIG. 3.
The brush seal segments 37 include brush seal bristles (a bristle section) 39, restraint bristles (a restraint section, a bundle of bristles) 41, an upstream support plate 43, and a downstream support plate 45 (a brake section).
The brush seal bristles 39 are formed of wires (bristles) 47 with a diameter of 0.1 to 0.2 mm (in this embodiment, for example, 0.13 mm) and a length of 30 to 40 mm, and are bundled together with a wire density of about 60 to 100 per 3 mm²(in a cross-sectional view parallel to the rotor axis).
The wires 47 are disposed at a predetermined angle relative to the radius of the downstream brush seal 29, that is, inclined in the rotating direction 10 of the downstream cylindrical portion 25 (see FIG. 3).
The wires 47 are made of a cobalt-based heat-resisting alloy, for example, HAYNES alloy (a trademark of Haynes International, Inc.) No. 25.
The outer circumferential ends of the brush seal bristles 39 are clamped by an upstream retainer 49 and a downstream retainer 51 which are rectangular cross-section arc-shaped components. The outer circumferential end faces of the brush seal bristles 39 are fixed across the upstream retainer 49 and the downstream retainer 51 by a weld 53.
The restraint bristles 41 are formed of wires (bristles) 55 with a diameter of 0.1 to 0.2 mm (in this embodiment, for example, 0.13 mm) and a length of 15 to 18 mm, and are bundled together with a wire density of about 60 to 100 per 3 mm²(in a cross-sectional view parallel to the rotor axis).
The wires 55 are made of a cobalt-based heat-resisting alloy, for example, HAYNES alloy (a trademark of Haynes International, Inc.) No. 25.
The wires 55 have low elasticity in themselves but can provide higher elasticity when bundled. The elasticity of the restraint bristles 41 can be adjusted to a predetermined value by adjusting the density of the wires 55.
The wires 55 are disposed at a predetermined angle relative to the radius of the downstream brush seal 29, that is, inclined in the rotating direction 10 of the downstream cylindrical portion 25 (see FIG. 3).
The outer circumferential end faces of the restraint bristles 41 are fixed to a restraint-bristle retainer 57 which is a rectangular cross-section arc-shaped component by a weld 59.
The upstream support plate 43 is a substantially rectangular cross-section arc-shaped component.
The upstream support plate 43 has, substantially at the center of the upstream surface in the radial direction, a recessed portion 61 in which a ring-shaped protruding portion 63 provided at the lower part of the installation space 22 in the seal box 21 is to be fitted.
The upstream support plate 43 has, in the vicinity of the outer circumference in the downstream surface in the radial direction, an upstream retaining groove 65 for accommodating the upstream retainer 49.
The width, that is, the radial length, of the upstream retaining groove 65 is set a little larger than the total length of the upstream retainer 49 and the weld 53.
The downstream surface of the upstream support plate 43 has, from the inner circumferential end to the vicinity of the upstream retaining groove 65, a restraint-bristle retaining recessed portion 67 for accommodating the restraint bristles 41.
The restraint-bristle retaining recessed portion 67 has a restraint-bristle retaining groove 69 for accommodating the restraint-bristle retainer 57 substantially at the center in the radial direction.
The width, that is, the radial length, of the restraint-bristle retaining groove 69 is set a little larger than the total length of the restraint-bristle retainer 57 and the weld 59.
The upstream surface of the upstream support plate 43 has, substantially in the radially outer circumference, a rotation stop groove 71 extending in the radial direction.
The downstream support plate 45 is a substantially rectangular cross-section arc-shaped component.
The downstream support plate 45 has, substantially in the center of the downstream surface in the radial direction, a recessed portion 75 in which a ring-shaped protruding portion 73 provided at the lower part of the installation space 22 in the seal box 21 is to be fitted.
The downstream support plate 45 has, in the vicinity of the outer circumference in the upstream surface in the radial direction, a downstream retaining groove 77 for accommodating the downstream retainer 51.
The width, that is, the radial length, of the downstream retaining groove 77 is set a little larger than the total length of the downstream retainer 51 and the weld 53.
The upstream surface of the downstream support plate 45 is cut off from the downstream retaining groove 77 to the inner circumferential end by a depth corresponding to the axial length of the brush seal bristles 39 so as to accommodate the brush seal bristles 39.
The upstream support plate 43 and the downstream support plate 45 are butted against each other, with the upstream retainer 49 accommodated in the upstream retaining groove 65 and the downstream retainer 51 accommodated in the downstream retaining groove 77, and with the restraint-bristle retainer 57 accommodated in the restraint-bristle retaining groove 69, and then the outer circumferences are joined to form the brush seal segment 37.
The brush seal segments 37 are combined in sequence so that the recessed portions 61 and 75 are fitted on the protruding portions 63 and 73 of the installation space 22 in the seal box 21, respectively.
At that time, a rotation stop bolt 79 fixed to the seal box 21 and to be engaged with the rotation stop groove 71 is mounted to define the circumferential positions of the individual brush seal segments 37 and to limit the circumferential movements of the individual brush seal segments 37.
The operation of the upstream brush seal 27 and the downstream brush seal 29 of this embodiment, having the above structure, will be described.
When the gas turbine 1 is started, combustion gas is supplied from a combustion apparatus (not shown) into the combustion gas passage 7.
The supplied combustion gas is expanded by the stationary blades 5 when flowing through the combustion gas passage 7 in the flowing direction 9 to generate velocity energy, so that it changes in flowing direction to produce kinetic energy in the axial rotating direction.
The combustion gas energy converted to the velocity energy is absorbed by the moving blades 3 to rotate them. The rotor rotates by this rotation of the moving blades 3. This rotating force rotates, for example, a generator (not shown) connected to the rotor to generate power.
Since the energy is thus absorbed by the individual moving blades 3 in sequence, the combustion gas is higher in temperature and pressure at the upstream side.
The larger the amount of combustion gas that passes through the combustion gas passage 7, the higher the energy efficiency is.
Therefore, the upstream brush seal 27, the downstream brush seal 29, and the labyrinth seal 33 seal combustion gas that moves from the first-row moving blade 3 a to the second-row moving blade 3 b without passing through the combustion gas passage 7.
When the gas turbine 1 is driven, the moving blades 3 are off-centered outwardly because a centrifugal force acts on the moving blades 3. The rotor and the stationary blades 5 are expanded because they are heated by the combustion gas.
This changes the distance between the seal box 21 at the stator side and the disk 11 at the rotor side, which generally brings them closer together.
When the seal box 21 and the disk 11 come close to each other in this way, the brush seal bristles 39 are pushed by the downstream cylindrical portion 25 to move to the outer circumference.
When the outer circumferential ends of the brush seal bristles 39 come into contact with the outer circumferential surface of the downstream retaining groove 77, the brush seal bristles 39 cannot move to the outer circumference any more, so that the brush seal bristles 39 are deflected.
At that time, the movement of the downstream ends of the brush seal bristles 39 is firmly limited by the downstream support plate 45, so that the brush seal bristles 39 are deflected upstream, that is, entirely moved upstream. That is, the entireties of the brush seal bristles 39 are moved, thus remarkably increasing pressure.
Thus, this prevents the brush seal bristles 39 from deflecting downstream, thereby preventing a decrease in sealing performance.
The brush seal bristles 39 are deflected toward the restraint bristles 41 mounted next thereto at the upstream side to apply high pressure thereto, whereas the restraint bristles 41 have a specific elasticity which is the total of the elasticity of the gaps among the wires 55 and the elasticity of the wires 55 themselves in the flowing direction 9, so that the restraint bristles 41 can absorb the movement of the brush seal bristles 39, that is, prevent the brush seal bristles 39 from moving by the elasticity.
Thus, the restraint bristles 41 absorb the contact pressure that acts between the brush seal bristles 39 and the downstream cylindrical portion 25, so that the contact frictional force therebetween is hardly increased.
Since the contact frictional force is not increased, an increase in steady-state wear can be prevented.
If turbulence occurs in the combustion gas flowing between the brush seal bristles 39 and the downstream cylindrical portion 25 to cause parts of the wires 47 to flutter, the force generated by the parts of the wires 47 is much smaller than that when the whole of the brush seal bristles 39 deflect.
Thus, this force is not large enough to overcome the elastic force of the restraint bristles 41 to deform them, so that this force does not deform the restraint bristles 41. In other words, the restraint bristles 41 can restrain the movement of parts of the wires 47.
This prevents the movement of parts of the wires 47 due to turbulence and prevents fluttering, thereby preventing breakage of the wires 47 caused by the fluttering.
This prevents the deterioration of the sealing performance of the downstream brush seal 29 and the upstream brush seal 27, thereby preventing, for example, a decrease in the output of the turbine and reducing the frequency of replacement of the brush seal, thus decreasing maintenance costs.
Since the end position of the restraint bristles 41 is separated from the surface of the downstream cylindrical portion 25 more than the end position of the brush seal bristles 39, there is little possibility that the restraint bristles 41 come into contact with the downstream cylindrical portion 25 even if the distance between the seal box 21 and the disk 11 at the rotor side is decreased.
Moreover, even if the restraint bristles 41 come into contact with the downstream cylindrical portion 25, there is little possibility that the surface of the downstream cylindrical portion 25 is worn down or damaged because the restraint bristles 41 are formed of the thin, weak wires 55.
The upstream brush seal 27 also operates in the same way as the downstream brush seal 29 described above.
The upstream brush seal 27 and the downstream brush seal 29 of this embodiment, described above, are not limited to the above description and may be modified variously without departing from the spirit of the present invention.
For example, while this embodiment uses the restraint bristles 41 which is a bundle of the wires 55 as a restraint section, the restraint section needs only enough elasticity to limit the movement of the wires 47 while absorbing the deflection of the brush seal bristles 39; for example, a thin sheet-like restraint section or a layer thereof may be used.
Although this embodiment is applied to the sealing structure between the stationary blades and the moving blades, the present invention is not limited to that and may be applied to other components.
Furthermore, the present invention is not necessarily applied to gas turbines but may be applied to other rotary machines, for example, a steam turbine.

Claims

1. A brush seal comprising:

a bristle section formed of a plurality of bristles and mounted to a stationary section in such a manner that one end thereof is in contact with a rotating section; and

a brake section mounted next to the bristle section in a direction in which fluid flows, for restricting the motion of the bristle section, the brush seal sealing the fluid flowing between the stationary section and the rotating section, wherein

the brush seal includes a restraint section mounted opposite to the brake section and next to the bristle section in the direction in which the fluid flows, the restraint section having a degree of elasticity such that the rotating section is not damaged even if coming into contact with the rotating section and such that the contact deformation of the bristle section is not hindered.

2. The brush seal according to claim 1, wherein the restraint section is disposed upstream of the bristle section in the direction in which the fluid flows.

3. The brush seal according to claim 1, wherein the restraint section is a bundle of bristles formed of a plurality of bristles whose end is farther away from the rotating section than the end of the bristles.

4. The brush seal according to claim 2, wherein the restraint section is a bundle of bristles formed of a plurality of bristles whose end is farther away from the rotating section than the end of the bristles.

5. A turbine that uses the brush seal according to claim 1.

6. A turbine that uses the brush seal according to claim 2.

7. A turbine that uses the brush seal according to claim 3.