U.S. patent application number 11/476270 was filed with the patent office on 2008-01-03 for brush sealing system and method for rotary machines.
This patent application is currently assigned to General Electric Company. Invention is credited to Nitin Bhate.
Application Number | 20080001363 11/476270 |
Document ID | / |
Family ID | 38875795 |
Filed Date | 2008-01-03 |
United States Patent
Application |
20080001363 |
Kind Code |
A1 |
Bhate; Nitin |
January 3, 2008 |
Brush sealing system and method for rotary machines
Abstract
A rotary machine includes a rotary component disposed inside a
stationary component. A brush sealing system is disposed between
the stationary component and the rotary component. The brush
sealing system includes a holding device coupled to the stationary
component. A plurality of carbon bristles is provided, each bristle
having a first end coupled to the holding device and a second end
protruding from the holding device towards the rotary component.
Diameter of each bristle is in the range of 0.1 to 1 mils.
Inventors: |
Bhate; Nitin; (Rexford,
NY) |
Correspondence
Address: |
GENERAL ELECTRIC COMPANY;GLOBAL RESEARCH
PATENT DOCKET RM. BLDG. K1-4A59
NISKAYUNA
NY
12309
US
|
Assignee: |
General Electric Company
|
Family ID: |
38875795 |
Appl. No.: |
11/476270 |
Filed: |
June 28, 2006 |
Current U.S.
Class: |
277/355 |
Current CPC
Class: |
F05D 2240/56 20130101;
F01D 11/003 20130101 |
Class at
Publication: |
277/355 |
International
Class: |
F01D 11/02 20060101
F01D011/02 |
Claims
1. A rotary machine, comprising: a stationary component; a rotary
component disposed inside the stationary component; and a brush
sealing system disposed between the stationary component and the
rotary component, comprising: a holding device coupled to the
stationary component; and a plurality of carbon bristles, each
bristle having a first end coupled to the holding device and a
second end protruding from the holding device towards the rotary
component; wherein diameter of each bristle is in the range of 0.1
to 1 mils.
2. The rotary machine of claim 1, wherein the holding device
comprises a first plate and a second plate configured to hold the
plurality of bristles.
3. The rotary machine of claim 2, wherein the first and second
plates comprise a metallic material, a composite material, or a
combination thereof.
4. The rotary machine of claim 1, further comprising a matrix
disposed between the first and second plates.
5. The rotary machine of claim 4, wherein the first end of each
bristle is coupled to the matrix disposed between the first and
second plates.
6. The rotary machine of claim 1, wherein strength of each bristle
is at least 900 kilopounds per inch squared.
7. The rotary machine of claim 1, wherein fiber modulus of each
bristle is at least 19 megapounds per inch squared.
8. The rotary machine of claim 1, wherein elongation of each
bristle during operation of the rotary machine is 2 percent.
9. The rotary machine of claim 1, wherein the second end of each
bristle is configured to contact the rotary component to reduce
leakage of pressurized fluid between the stationary component and
the rotary component during operation of the machine.
10. The rotary machine of claim 1, wherein the brush sealing system
is coupled to a labyrinth sealing element recessed partially in the
stationary component.
11. The rotary machine of claim 1, wherein the rotary machine
comprises an electric generator.
12. The rotary machine of claim 1, wherein the rotary machine
comprises a gas turbine.
13. A brush sealing system, comprising: a holding device coupled to
a stationary component; and a plurality of carbon bristles, each
bristle having a first end coupled to the holding device, a second
end protruding from the holding device towards a rotary component
and configured to contact the rotary component to reduce leakage of
pressurized fluid between the stationary component and the rotary
component; wherein diameter of each bristle is in the range of 0.1
to 1 mils.
14. The brush sealing system of claim 13, wherein the holding
device comprises a first plate and a second plate configured to
hold the plurality of bristles.
15. The brush sealing system of claim 14, wherein the first and
second plates comprise a metallic material, a composite material,
or a combination thereof.
16. The brush sealing system of claim 13, further comprising a
matrix disposed between the first and second plates.
17. The brush sealing system of claim 16, wherein the first end of
each bristle is coupled to the matrix disposed between the first
and second plates.
18. The brush sealing system of claim 13, wherein strength of each
bristle is at least 900 kilopounds per inch squared.
19. The brush sealing system of claim 13, wherein fiber modulus of
each bristle is at least 19 megapounds per inch squared.
20. The brush sealing system of claim 13, wherein elongation of
each bristle during rotation of the rotary component is 2
percent.
21. A brush sealing system, comprising: a holding device coupled to
a stationary component; and a plurality of carbon bristles, each
bristle having a first end coupled to the holding device and a
second end protruding from the holding device towards the rotary
component; wherein each carbon bristle has friction coefficient
less than or equal to 0.25, thermal conductivity greater than 8
watts per meter-kelvin, and temperature capability greater than 700
degrees fahrenheit.
22. The brush sealing system of claim 21, wherein the holding
device comprises a first plate and a second plate configured to
hold the plurality of bristles.
23. The brush sealing system of claim 22, further comprising a
matrix disposed between the first and second plates.
24. The brush sealing system of claim 23, wherein the first end of
each bristle is coupled to the matrix disposed between the first
and second plates.
25. The brush sealing system of claim 21, wherein diameter of each
bristle is in the range of 0.1 to 1 mils.
26. The brush sealing system of claim 21, wherein the second end of
each bristle is configured to contact a rotary component to reduce
leakage of pressurized fluid between the stationary component and
the rotary component.
27. A method of operating a rotary machine, comprising: rotating a
rotary component disposed inside a stationary component; and
contacting a plurality of carbon bristles of a brush sealing system
against the rotary component to reduce leakage of a pressurized
fluid between the stationary component and the rotary component
during operation of the machine; wherein diameter of each bristle
is in the range of 0.1 to 1 mils.
28. The method of claim 27, further comprising biasing the brush
sealing system coupled to a labyrinth sealing element against the
rotary component to reduce leakage of pressurized fluid between the
stationary component and the rotary component during operation of
the machine.
29. The method of claim 28, further comprising biasing the brush
sealing coupled to the labyrinth sealing element away from the
rotary component during non-operating condition of the machine.
Description
BACKGROUND
[0001] The invention relates generally to a rotary machine and,
more particularly, a sealing system for an interface between
rotating and stationary components. As discussed below, certain
embodiments of the invention include a brush sealing system for a
rotary machine, and a method of operating a rotary machine for
minimizing leakage of fluid during operating conditions of the
machine.
[0002] Efficiency of rotary machines utilized for pumping a fluid,
or compressing, or expanding a vapor (e.g. gas) depends upon the
internal tolerances of the components comprising the machine. A
loosely-toleranced rotary machine may have a relatively poor fit
between internal components and may therefore exhibit poor
efficiency, with relatively high leakage occurring within the
device from regions of high pressure to regions of lower pressure.
The traditional approach to this situation is to decrease the
amount of clearance on these critical interfaces.
[0003] Sealing systems are used in rotary machines to reduce
leakage of fluid flowing through the rotary machines. One or more
seals extend along an interface between rotating and stationary
components. For example, compressors and turbines may have one or
more seals, e.g., labyrinth seals, at the interface between a
series of rotating blades disposed within a casing or vane. These
seals are intended to preserve a pressure differential across the
rotating components, e.g., blades, between upstream and downstream
sides of the rotary machine. In certain other examples, seals are
also used in bearing sump systems to limit the amount of gas
required to vent the sumps. The seals are usually subjected to
relatively high temperatures, thermal gradients, and thermal
expansion and contraction of the components during various
operational stages. For example, the clearance can increase or
decrease during various operational stages of the rotary machine.
Typically, the labyrinth seal includes extra clearance to reduce
the likelihood of contact and damage between the rotating and
stationary components. However, the extra clearance also reduces
the efficiency and performance of the rotary machine, because extra
leakage occurs across the seal.
[0004] In another example, circumferential seals are used at the
interface between the rotating and stationary components. Typically
in a gas turbine engine, a plurality of stationary shroud segments
are assembled circumferentially about an axial flow engine axis and
radially outwardly about rotatable blade members, for example about
turbine blades, to define a part of the radial outer flow path
boundary over the blades. The circumferential seals facilitate
maintaining tight clearance between the rotating and stationary
components. However, circumferential seals generate higher
interface temperatures leading to wear and larger clearance between
the rotating and the stationary components. In yet another example,
polymer brush seals are disposed between the rotating and
stationary components. However, polymer brush seals generate higher
interface temperature leading to wear and larger clearance between
the rotating and the stationary components during transient
operating conditions of the machine.
[0005] Accordingly, there is a need for a technique that reduces
leakage of fluid in a rotary machine, and that maintains minimum
clearance without impairing the performance of a seal during all
operating conditions. In addition, a system for reducing leakage of
fluid in a rotary machine during all operating conditions is also
desirable. A plurality of carbon bristles are provided, each
bristle having a first end coupled to the holding device and a
second end protruding from the holding device towards the rotary
component.
BRIEF DESCRIPTION
[0006] In accordance with one aspect of the present invention, a
rotary machine includes a rotary component disposed inside a
stationary component. A brush sealing system is disposed between
the stationary component and the rotary component. The brush
sealing system includes a holding device coupled to the stationary
component. A plurality of carbon bristles is provided, each bristle
having a first end coupled to the holding device and a second end
protruding from the holding device towards the rotary component.
The diameter of each bristle is in the range of 0.1 to 1 mils.
[0007] In accordance with another aspect of the present invention,
a brush sealing system includes a holding device coupled to a
stationary component. A plurality of carbon bristles are provided,
each bristle having a first end coupled to the holding device, a
second end protruding from the holding device towards a rotary
component and configured to contact a rotary component to reduce
leakage of pressurized fluid between the stationary component and
the rotary component.
[0008] In accordance with another aspect of the present invention,
a brush sealing system includes a holding device coupled to a
stationary component. A plurality of carbon bristles are provided,
each bristle having a first end coupled to the holding device and a
second end protruding from the holding device towards the rotary
component. Each carbon bristle has a friction coefficient less than
or equal to 0.25, thermal conductivity greater than 8 watts per
meter-Kelvin, and temperature capability greater than 700 degrees
fahrenheit.
[0009] In accordance with another aspect of the present invention,
a method of operating a rotary machine includes rotating a rotary
component disposed inside a stationary component. A plurality of
carbon bristles of a brush sealing system are contacted against the
rotary component to reduce leakage of a pressurized fluid between
the stationary component and the rotary component during operation
of the machine; wherein diameter of each bristle is in the range of
0.1 to 1 mils.
DRAWINGS
[0010] These and other features, aspects, and advantages of the
present invention will become better understood when the following
detailed description is read with reference to the accompanying
drawings in which like characters represent like parts throughout
the drawings, wherein:
[0011] FIG. 1 is a diagrammatical view of rotary machine, e.g., an
electrical generator including a plurality of brush seals in
accordance with an exemplary embodiment of the present
invention;
[0012] FIG. 2 is a diagrammatical view of a brush seal segment of a
brush seal in accordance with the aspects of FIG. 1;
[0013] FIG. 3 is a diagrammatical view of a brush seal segment in
accordance with aspects of FIG. 2;
[0014] FIG. 4 is a cross sectional view of a combination
labyrinth/brush seal in a packing ring segment of a stationary
component of a turbine sealing biased against a rotary component in
accordance with an exemplary aspect of the present invention;
and
[0015] FIG. 5 is a diagrammatical view of a brush seal in
accordance with aspects of FIG. 4.
DETAILED DESCRIPTION
[0016] As discussed in detail below, embodiments of the present
invention provide a rotary machine (for example, an electric
generator, a gas turbine, or the like) in which a brush sealing
system is disposed between a stationary component and a rotary
component. The sealing system includes a holding device coupled to
the stationary component. The exemplary sealing system includes a
plurality of carbon fibers or bristles coupled to the holding
device and configured to contact the rotary component. In
accordance with aspects of the present invention, the parameters
(such as friction coefficient, thermal conductivity, temperature
capability, or the like) of the carbon fibers are chosen so as to
maintain minimal clearances between the rotary component and the
surrounding stationary component resulting in reduced fluid leakage
and increased efficiency of the rotary machine. The bristle
material also facilitates minimizing interface temperature between
the sealing system and the rotary component during operation of the
machine. Specific embodiments of the present invention are
discussed below referring generally to FIGS. 1-5.
[0017] Referring to FIG. 1, a rotary machine 10 includes a brush
sealing system 11 having two brush seals 12, 14. One of the brush
seal 12 is shown in greater detail in the subsequent figures. In
accordance with aspects of the present invention, the brush seal 14
is similar or generally identical to the brush seal 12, and the
description of the brush seal 12 below also serves a description of
the brush seal 14. In the illustrated embodiment, the rotary
machine 10 is an electric generator. In other examples, without
limitation, the rotary machine 10 may be a centrifugal compressor,
or a steam turbine, or a gas turbine, or a bearing, or a sump, or
the like. It may also be noted that the aspects of the present
invention are not limited to an association with the rotary machine
and may be associated with other machines subjected to fluid
pressure drop during machine operation.
[0018] In the illustrated embodiment, the rotary machine 10
includes a stator 16, and a rotor 18 coaxially aligned with the
stator 16. The rotor 18 is radially spaced apart from the stator 16
to define a gap 20 between the stator 16 and the rotor 18. Although
in the illustrated embodiment, the stator 16 circumferentially
surrounds the rotor 18, certain other applications require the
rotor to circumferentially surround the stator as known to those
skilled in the art. A fluid 21 is disposed in the gap 20 in such a
way that the fluid 21 has a pressure drop generally transverse to
the gap 20. The pressure drop is generated during operation of the
machine 10. The brush seal 12 in accordance with aspects of the
present invention includes a plurality of graphite or carbon
bristles 22 configured to contact the rotor 18 to reduce leakage of
fluid and also reduce temperature at a seal-rotor interface. The
brush seal 12 is explained in greater detail with respect to
subsequent figures below.
[0019] Referring to FIG. 2, the brush seal 12 includes a holding
device 24 coupled to the stator 16. The plurality of carbon
bristles 22 are coupled to the holding device 24. In accordance
with aspects of the present invention, each carbon bristle 22 has a
diameter in the range of 0.1 to 1 mils. Even though in the
illustrated embodiment pertains to carbon bristles, aspects of the
present invention may also be applicable to other non-metallic
bristles. Typically, the bristles 22 are canted at an angle, for
example, forty-five degrees angle. As known to those skilled in the
art, the canting of bristles 22 improves the compliance of the seal
with the rotor 18.
[0020] Referring to FIG. 3, brush 12 in accordance with an
exemplary aspect of the present invention is illustrated. Each
bristle 22 includes a first end 34 coupled to the holding device 24
and a second end 36 disposed proximate to the rotor 18. In certain
exemplary embodiments, the second end of the bristle is configured
to contact the rotor 18. In the illustrated embodiment, the holding
device 24 includes a first plate 38, a second plate 40, and a
matrix 42 disposed between the first plate 38 and the second plate
40. In certain exemplary embodiments, the first and second plates
38, 40 include a metallic material, or a composite material, or a
combination thereof. The bristles 22 are clamped between the first
and the second plates 38, 40. The first end 34 of each bristle 22
is coupled to the matrix 42 and the second end 36 protrudes from
the plates 38, 40 towards the rotor 18. The matrix 42 may include
epoxy, polyimide, or the like.
[0021] Typically, the conventional brush sealing system is
configured to contact the rotor 18 thereby generating frictional
heat at the seal-rotor interface during operation of the machine.
The heat generated at the seal-rotor interface may be dissipated by
convection, conduction through the brush seal, conduction through
the rotor, or the like. When conventional brush seals are used,
temperature at the seal-rotor interface increases, resulting in
expansion of the rotor 18. The rotor expansion leads to higher
interference between the brush seal and the rotor 18 causing brush
seal wear and increased leakage of fluid between the rotor 18 and
the stator. This reduces efficiency of the rotary machine.
[0022] The carbon bristles 22 in accordance with aspects of the
present invention facilitates minimizing seal wear and maintaining
temperature at the seal-rotor interface minimum. In certain
exemplary embodiments, the brush seal 12 has the following
parameters in order maintain a minimum temperature at seal-rotor
interface. One effective bristle material of the brush seal has a
friction coefficient less than 0.25, thermal conductivity greater
than 8 watts per meter-kelvin (W/mK), and a temperature capability
greater than 700 degrees fahrenheit. It should be noted that the
values of the above mentioned parameters are exemplary values and
should not be construed as limiting values. The combination of
friction coefficient and thermal conductivity parameter of the
bristle material of the brush seal 12 facilitates minimizing rotor
expansion and ensuring adequate heat dissipation via conduction
through the seal 12. The temperature capability parameter of the
bristle material of the brush seal 12 facilitates minimizing seal
wear resulting from higher temperature at the rotor-seal interface.
In certain exemplary embodiments, the bristle material includes
carbon or graphite. In certain other exemplary embodiments, the
seal material may include other non-metallic material. In
accordance with aspects of the present invention, the diameter of
each bristle is maintained in the range of 0.1 to 1 mils so that a
clearance of 0.1 mils may be maintained between the brush seal 12
and the rotor 18.
[0023] Referring to FIG. 4, a combination labyrinth/brush sealing
system 44 in accordance with aspects of the present invention is
illustrated. The sealing system 44 is disposed in a groove 46 of a
stationary component 48 of a rotary machine 50 (for example, gas
turbine). The sealing system 44 includes a packing ring segment 52
(labyrinth sealing element) disposed in the groove 46 of the
stationary component 48. The packing ring segment 52 includes two
sealing flanges 51 extending axially beyond a neck opening 54 of
the groove 46. A hook flange 56 is configured surrounding the neck
opening 54. As known to those skilled in the art, the groove 46
extends circumferentially along the stationary component 48. A
rotary component (for example, a shaft) 58 is disposed inside the
stationary component 48. It should be noted that although one
packing ring segment 52 is illustrated, a plurality of packing ring
segments may be configured similarly between the stationary
component 48 and the rotary component 58. The packing ring segment
52 includes a plurality of tapered teeth 60 extending radially
inward disposed proximate to, but spaced from recesses 62 formed on
the rotary component 58 to form a labyrinth seal between the
packing ring segment 52 and the rotary component 58.
[0024] An exemplary brush seal 64 is provided in the packing ring
segment 52. The brush seal 64 in accordance with aspects of the
invention includes a plurality of circumferentially extending array
of carbon bristles 66 provided between a pair of side plates 68,
70. The side plate 68 extends short of the rotary component surface
whereas the other side plate 70 forms a tapered tooth 69 similar to
the tapered tooth 60 of the labyrinth seal. The tapered tooth 60
forms part of the labyrinth seal and also forms a backing plate at
a low pressure side of the bristles 66. The tips of the bristles 66
are configured to contact the rotary component 58 forming a brush
seal therewith. The brush seal 64 is provided in a groove, which
extends circumferentially in the packing ring segment 52. In
accordance with aspects of the present invention, each carbon
bristle 66 has a diameter in the range of 0.1 to 1 mils. The carbon
bristles 66 facilitate to minimize seal wear and maintain
temperature at the seal-rotary component interface minimum. In
certain exemplary embodiments, the carbon bristles have the
following properties: strength-900 Ksi (kilopounds per inch
squared), fiber modulus-19 Msi (Megapounds per inch squared),
elongation-2%, service temperature-930 degrees fahrenheit, thermal
conductivity-11.8 W/mK (watts per meter-kelvin). Smaller diameter
of carbon bristles results in lower effective clearance at the
seal-rotary component interface, and also lower stiffness resulting
in lower heat generation. Greater strength of the carbon bristles
results in greater stress capability. Higher thermal conductivity
of the carbon bristles results in lower temperature at the
seal-rotary component interface.
[0025] In certain exemplary embodiments, a plurality of springs may
be provided between axially opposite flanges 51 of the packing ring
segment 52 and the hook flanges 56 of the groove 46. The springs
are configured to displace the packing ring segment radially
outwards. Pressurized fluid may be introduced into the groove 46
via a passage 63 provided in the stationary component 48 for
displacing the packing ring segment 52 radially inwards, for
example, during steady state operating conditions of the rotary
component 58 to effectively seal between high and low pressure
regions 65, 67 respectively of the machine. In certain exemplary
embodiments, the bristles 66 may be provided side-by-side along
both circumferential and axial directions thereby providing a
tortuous path between the bristles 66 for fluid flow between high
and low pressure regions 65, 67 respectively of the machine.
[0026] Referring now to FIG. 5, the brush seal 64 in accordance
with the aspects of FIG. 4 is illustrated. The brush seal 64 in
accordance with the exemplary embodiment includes the plurality of
circumferentially extending array of carbon bristles 66 provided
between the pair of side plates 68, 70. As discussed previously,
the side plate 68 extends short of the rotary component surface
whereas the other side plate 70 forms the tapered tooth 69. One end
71 of the bristles 66 is coupled to a matrix 72 disposed between
the side plates 68, 70. Other end 73 of the bristles 66 protrudes
beyond the side plates 68, 70 towards the rotary component surface.
The side plate 68 includes one flow channel 74 whereas the other
side plate 70 includes a plurality of grooves 76. The flow channel
74 and the grooves 76 are configured facing the bristles 66. The
flow channel 74 and the grooves 76 facilitate to provide pockets to
reduce contact between the bristles 66 and the side plates 68, 70.
In certain exemplary embodiments, the side plates 68, 70 include a
metallic material, or a composite material, or a combination
thereof. Pressurized fluid may be directed through the channel 74,
grooves 76, and against the bristles 66 disposed between the plates
68, 70. The fluid deflects the bristles 66 towards the rotary
component such that tip of the bristles contact the surface of the
rotary component to maintain a seal thereagainst.
[0027] As discussed previously, in certain exemplary embodiments,
bristle material of the brush seal 64 has a friction coefficient
less than 0.25, thermal conductivity greater than 8 watts per
meter-kelvin (W/mK), and a temperature capability greater than 700
degrees fahrenheit. The combination of friction coefficient and
thermal conductivity parameter of the bristle material of the brush
seal 64 facilitates minimizing rotor expansion and ensuring
adequate heat dissipation via conduction through the seal 64. The
temperature capability parameter of the bristle material of the
brush seal 64 facilitates minimizing seal wear resulting from
higher temperature at the rotary component-seal interface.
[0028] While only certain features of the invention have been
illustrated and described herein, many modifications and changes
will occur to those skilled in the art. It is, therefore, to be
understood that the appended claims are intended to cover all such
modifications and changes as fall within the true spirit of the
invention.
* * * * *