U.S. patent application number 11/411184 was filed with the patent office on 2007-10-25 for retractable compliant abradable sealing system and method for rotary machines.
Invention is credited to Bruce William Brisson, Kripa Kiran Varanasi, Christopher Edward Wolfe.
Application Number | 20070248452 11/411184 |
Document ID | / |
Family ID | 38619622 |
Filed Date | 2007-10-25 |
United States Patent
Application |
20070248452 |
Kind Code |
A1 |
Brisson; Bruce William ; et
al. |
October 25, 2007 |
Retractable compliant abradable sealing system and method for
rotary machines
Abstract
An abradable structure is provided on an inner face of a
stationary component of the rotary machine or on a rotating
component. During operation of the rotary machine, operating fluid
pressure biases the stationary component against the rotating
component, allowing minimal clearances to be maintained between the
rotating component and the stationary component resulting in
reduced fluid leakage and increased efficiency of the rotary
machine. During start-up, shut down, or other transient conditions
of the machine, a retractable mechanism biases the stationary
component away from the rotating component ensuring preservation of
a plurality of teeth provided on the stationary component or the
rotating component.
Inventors: |
Brisson; Bruce William;
(Galway, NY) ; Wolfe; Christopher Edward;
(Niskayuna, NY) ; Varanasi; Kripa Kiran; (Clifton
Park, NY) |
Correspondence
Address: |
GENERAL ELECTRIC COMPANY (PCPI);C/O FLETCHER YODER
P. O. BOX 692289
HOUSTON
TX
77269-2289
US
|
Family ID: |
38619622 |
Appl. No.: |
11/411184 |
Filed: |
April 25, 2006 |
Current U.S.
Class: |
415/10 |
Current CPC
Class: |
F16J 15/445 20130101;
F01D 11/06 20130101; F01D 19/00 20130101 |
Class at
Publication: |
415/010 |
International
Class: |
F01D 19/00 20060101
F01D019/00 |
Claims
1. A rotary machine, comprising: a first member; a second member,
wherein the first member is configured to rotate relative to the
second member or the second member is configured to rotate relative
to the first member; and a retractable abradable seal disposed
between the first and second members.
2. The rotary machine of claim 1, wherein the retractable abradable
seal configured to provide a generally zero-clearance labyrinth
seal between the first and second members.
3. The rotary machine of claim 1, wherein the retractable abradable
seal comprises an abradable structure coupled to a retractable
mechanism.
4. The rotary machine of claim 3, wherein the retractable mechanism
is recessed at least partially into the second member.
5. The rotary machine of claim 1, wherein the retractable abradable
seal comprises a retractable seal portion coupled to the second
member and an abradable seal portion coupled to the first member
opposite from the retractable seal portion.
6. The rotary machine of claim 1, wherein the retractable abradable
seal comprises an abradable seal portion disposed opposite from one
or more sealing teeth.
7. The rotary machine of claim 6, wherein the plurality of teeth
are configured to form a plurality of permanent sealing grooves in
the abradable seal portion.
8. The rotary machine of claim 7, wherein the plurality of teeth
are configured to engage the plurality of permanent sealing grooves
formed in the abradable seal portion during normal operation of the
machine.
9. The rotary machine of claim 1, wherein the rotary machine
comprises a turbine, a compressor, a combustor, or a combination
thereof.
10. The rotary machine of claim 1, wherein the rotary machine
comprises a steam turbine.
11. A system, comprising: a retractable abradable seal, comprising:
a retractable mechanism configured to couple to a second member
opposite from a first member, wherein the first member or the
second member is configured to rotate; a first seal portion
disposed on the retractable mechanism; and a second seal portion
configured to be disposed on the first member and mate with the
first seal portion, wherein the first seal portion or the second
seal portion comprises an abradable structure.
12. The system of claim 11, wherein the retractable abradable seal
is configured to provide a generally zero-clearance labyrinth seal
between the first and second members.
13. The system of claim 11, wherein the first member comprises a
rotary member.
14. The system of claim 11, wherein the second member comprises a
stationary member.
15. The system of claim 11, wherein the abradable structure
comprises an abradable coating.
16. The system of claim 11, wherein the abradable structure
comprises cobalt, or, nickel, or, chromium, or, aluminum, or,
yttrium, or, hexagonal boron nitride, or polymers, or a combination
thereof.
17. The system of claim 11, wherein the abradable structure
comprises nickel, or, chromium, or, aluminum, or clay, or a
combination thereof.
18. The system of claim 11, wherein the abradable structure
comprises nickel, or, graphite, or, stainless steel, or a
combination thereof.
19. The system of claim 11, wherein the abradable structure
comprises nickel, or, chromium, or, iron, or, aluminum, or, boron,
or nitrogen, or a combination thereof.
20. The system of claim 11, wherein the abradable structure
comprises a plurality of drilled holes configured to reduce
vibration.
21. The system of claim 11, wherein the retractable mechanism
comprises one or more springs configured to bias the first seal
portion away from the second seal portion.
22. The system of claim 11, wherein the retractable mechanism
comprises one or more permanent magnets, or electromagnets
configured to bias the first seal portion away from the second seal
portion.
23. The system of claim 11, wherein the first seal portion
comprises the abradable structure and the second seal portion
comprises one or more sealing teeth, or the first seal portion
comprises one or more sealing teeth and the second seal portion
comprises the abradable structure, or a combination thereof.
24. The system of claim 23, wherein the plurality of sealing teeth
are configured to form a plurality of permanent sealing grooves in
the abradable structure.
25. The system of claim 24, wherein the plurality of sealing teeth
are configured to engage the plurality of permanent sealing grooves
formed in the abradable structure during normal operation of the
system.
26. The system of claim 11, wherein the retractable mechanism is
disposed at least partially in a gas chamber.
27. The system of claim 11, wherein the retractable mechanism
comprises a first stopper and a second stopper opposite the first
stopper, and the first and second stoppers are configured to limit
a range clearance between the first and second seal portions.
28. A method, comprising: rotating a first member relative to a
second member or rotating the second member relative to the first
member; and providing a zero-clearance labyrinth seal between the
first and the second members via a retractable abradable seal
disposed between the first and the second members.
29. The method of claim 28, wherein providing a zero-clearance
labyrinth seal comprises biasing a retractable seal portion coupled
to the second member against an abradable seal portion coupled to
the first member.
30. The method of claim 28, wherein providing a zero-clearance
labyrinth seal comprises biasing an abradable seal portion coupled
to the second member against one or more sealing teeth coupled to
the first member.
31. The method of claim 30, wherein providing a zero-clearance
labyrinth seal comprises abrading a coating formed in the abradable
seal portion to form a plurality of permanent sealing grooves in
the coating.
32. The method of claim 30, further comprising biasing the
abradable seal portion away from one or more seal teeth via one or
more springs.
33. The method of claim 30, wherein providing a zero-clearance
labyrinth seal comprises limiting a range clearance between the
abradable seal portion and one or more sealing teeth via a first
stopper and a second stopper.
34. A method, comprising: disposing a retractable abradable seal
between a first member and a second member, comprising coupling a
retractable mechanism to the second member opposite from the first
member, wherein the first member or the second member is configured
to rotate; disposing a first seal portion on the retractable
mechanism; and disposing a second seal portion on the first member
to mate with the first seal portion; wherein the first seal portion
or the second seal portion comprises an abradable structure.
35. The method of claim 34, wherein disposing the retractable seal
between the first and second members comprises providing a
zero-clearance labyrinth seal between the first and second
members.
36. The method of claim 34, comprising providing an abradable
coating on the first seal portion or the second seal portion.
37. The method of claim 34, wherein coupling the retractable
mechanism comprises providing one or more springs configured to
bias the first seal portion away from the second seal portion.
38. The method of claim 37, comprising disposing the retractable
mechanism at least partially in a gas chamber.
39. The method of claim 37, wherein disposing the retractable
mechanism comprises providing a first stopper and a second stopper
opposite the first stopper and configured to limit a range
clearance between the first and second members.
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 retractable abradable
sealing system for a rotary machine, and a method of operating a
rotary machine for facilitating a minimum dynamic clearance during
steady state and transient operating conditions of the rotary
machine.
[0002] In 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. A smaller clearance at the seal generally increases the
performance of the seal. Unfortunately, the rotating components,
e.g., blades, increase the difficulty in attaining and maintaining
a smaller clearance at the seal. In certain rotary machines, such
as gas turbine engines, the seals are subject 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 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.
[0003] 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 steady
state operating conditions and maintains clearance at all operating
points during transient operating conditions. In addition, a system
for reducing leakage of fluid in a rotary machine during steady
state and transient operating conditions is also desirable.
BRIEF DESCRIPTION
[0004] In accordance with one aspect of the present invention, a
rotary machine comprises a first member, and a second member,
wherein the first member is configured to rotate relative to the
second member or the second member is configured to rotate relative
to the first member. A retractable abradable seal is disposed
between the first and second members.
[0005] In accordance with another aspect of the present invention,
a system comprises a retractable abradable seal. The seal comprises
a retractable mechanism configured to couple to a second member
opposite from a first member, wherein the first member or the
second member is configured to rotate. A first seal portion is
disposed on the retractable mechanism. A second seal portion is
configured to be disposed on the first member and mate with the
first seal portion, wherein the first seal portion or the second
seal portion comprises an abradable structure.
[0006] In accordance with another aspect of the present invention,
a method of operating a rotary machine includes rotating a first
member relative to a second member or rotating the second member
relative to the first member. The method also includes providing a
zero-clearance labyrinth seal between the first and the second
members via a retractable abradable seal disposed between the first
and the second members.
[0007] In accordance with another aspect of the present invention,
a method of manufacturing a rotary machine includes disposing a
retractable abradable seal between a first member and a second
member. The method also includes coupling a retractable mechanism
to a second member opposite from a first member, wherein the first
member or the second member is configured to rotate. A first seal
portion is disposed on the retractable mechanism. A second seal
portion is disposed on the first member to mate with the first seal
portion; wherein the first seal portion or the second seal portion
comprises an abradable structure.
DRAWINGS
[0008] 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:
[0009] FIG. 1 is a diagrammatical view of a gas turbine engine
system having a retractable abradable sealing system in accordance
with an exemplary embodiment of the present invention;
[0010] FIG. 2 is a diagrammatical view of a retractable abradable
sealing system for a rotary machine, e.g., a compressor, in
accordance with aspects of FIG. 1;
[0011] FIG. 3 is a diagrammatical view of a retractable abradable
sealing system for a rotary machine, e.g., a compressor, in
accordance with aspects of FIG. 1;
[0012] FIG. 4 is a cross sectional view of an abradable coating
having drilled holes in accordance with aspects of FIG. 2;
[0013] FIG. 5 is an axial view of a retractable abradable sealing
system for a rotary machine, e.g., a compressor, in accordance with
an exemplary embodiment of the present invention;
[0014] FIG. 6 is a diagrammatical view of a retractable abradable
sealing system having a plurality of teeth detachably fitted to a
rotating component of a rotary machine, e.g., a compressor, in
accordance with an exemplary embodiment of the present
invention;
[0015] FIG. 7 is a diagrammatical view of a retractable abradable
sealing system for a rotary machine, e.g., a compressor, in
accordance with an exemplary embodiment of the present
invention;
[0016] FIG. 8 is a diagrammatical view of a retractable abradable
sealing system for a rotary machine, e.g., a steam turbine, in
accordance with an exemplary embodiment of the present
invention;
[0017] FIG. 9 is a flow chart illustrating exemplary steps involved
in a method of operating a retractable abradable sealing system in
accordance with an exemplary embodiment of the present invention;
and
[0018] FIG. 10 is flow chart illustrating exemplary steps involved
in method of manufacturing a retractable abradable sealing system
in accordance with an exemplary embodiment of the present
invention.
DETAILED DESCRIPTION
[0019] As discussed in detail below, embodiments of the present
invention provide a rotary machine, in which operating fluid
pressure opposes pressure exerted by a retractable mechanism in the
rotary machine. An abradable structure is provided on an inner face
of a stationary component of the rotary machine or on a rotating
component. During operation of the rotary machine, operating fluid
pressure biases the stationary component against the rotating
component, allowing minimal clearances to be maintained between the
rotating component and the stationary component resulting in
reduced fluid leakage and increased efficiency of the rotary
machine. The rotating component is rotatable relative to the
stationary component to form a plurality of permanent sealing
grooves in the stationary component or in the rotating component
due to interference. During start-up, shut down, or other transient
conditions of the machine, the retractable mechanism biases the
stationary component away from the rotating component ensuring
preservation of a plurality of teeth provided on the stationary
component or the rotating component. The rotary machine, in
accordance with aspects of the present invention, facilitates
removal of the rotating component from the seal cavity of the
machine for maintenance. Specific embodiments of the present
invention are discussed below referring generally to FIGS.
1-10.
[0020] Referring to FIG. 1, an exemplary rotary machine (example,
gas turbine engine system) 10 is illustrated in accordance with
aspects of the present invention. The illustrated machine 10
includes a gas turbine engine 12 having a compressor 14, a turbine
16, and a gas turbine shaft 18 coupling the compressor 14 rotatably
to the turbine 16. The gas turbine engine 12 also includes one or
more combustors 20, such as an annular or can-shaped combustor. The
gas turbine engine 12 also may be coupled to a variety of loads 22.
Furthermore, the gas turbine engine 12 includes a retractable
abradable sealing system 24 disposed in the compressor 14 and/or
the turbine 16. The retractable abradable sealing system 24 is
discussed in further detail below.
[0021] The compressor 14 is coupled to the combustor 20 to supply
compressed air into the combustor 20. The temperature of the
compressed air generally increases due to compression. The
compressed air mixes with a fuel (e.g., natural gas) and combusts
inside the combustor 20, thereby producing hot products of
combustion. The turbine 16 extracts energy by expansion of the hot
products of combustion for rotating the gas turbine shaft 18
coupled to the compressor 14. More specifically, an outlet of the
combustor 20 is coupled to an inlet of the turbine 16 to force the
hot products of combustion through one or more sets of blades
within the turbine 16. As a result, the hot products of combustion
force the blades and, thus, the shaft 18 to rotate about an axis of
the gas turbine engine 12. In turn, the rotating shaft 18 drives
the compressor 14, which continues to supply compressed air to the
combustor 20. In addition, the load 22 may be mechanically coupled
to the turbine 16. The gas turbine engine 12 is operated to
maintain the load 22 at a desired speed and other characteristics.
In other embodiments, the load 22 may include a power generator, a
pump, a propeller of an aircraft or watercraft, an industrial
machine, one or more wheels of a land vehicle, and so forth. Of
course, the illustrated engine system is merely an example, as the
present invention affords benefits to any number of systems in
which steam or gas leakage is a concern. In another exemplary
embodiment, the rotary machine may include a centrifugal
compressor.
[0022] Gas leakage, either out of a gas path, or into the gas path
of the rotary machine 10 from an area of higher pressure to an area
of lower pressure, is generally undesirable. For example, a gas
path leakage in the turbine 16 and/or compressor 14 of the rotary
machine 10 may lower the efficiency of the gas turbine leading to
increased fuel costs. In the illustrated embodiment, the
retractable abradable sealing system 24 is provided in the
compressor 14 and/or the turbine 16. The retractable abradable
sealing system 24 facilitates minimum clearance between a
stationary component and a rotating component in the compressor
and/or turbine. As a result, fluid leakage through the rotary
machine is minimized and the overall efficiency is enhanced. The
retractable abradable sealing system 24 in accordance with aspects
of the present invention, are explained in greater detail with
respect to subsequent figures.
[0023] Referring to FIG. 2, a rotary machine (for example, the
rotary compressor) 14 is illustrated in accordance with certain
embodiments of the present invention. In the illustrated embodiment
the rotary compressor 14 includes a first member 26 disposed inside
a second member 28. The first member 26 comprises a rotor and the
second member 28 comprises a stator or stationary housing. In an
alternate embodiment, the first member 26 may include the stator or
stationary housing and the second member 28 may include the rotor.
The first member or rotor 26 is coupled to an input drive shaft
extending lengthwise relative to the illustrated rotor 26, such
that the rotor can rotate about an axis 23 as illustrated by
rotational arrow 25. The second member or stator housing 28
includes a plurality of suction ports and discharge ports
communicating gases to or from the rotor 26. During rotation of the
rotor 26, fluid is sucked through the suction ports and the
compressed fluid is discharged through the discharge ports. The
retractable abradable sealing system 24 is provided between the
rotor 26 and the stator housing 28 and configured to control the
leakage of fluid between the rotor 26 and the stator housing 28.
Although in the illustrated embodiment, the rotary compressor is
illustrated, in other exemplary embodiments, the sealing system in
accordance with the aspects of the present invention may be used in
other rotary machines, for example, a steam turbine, a compressor,
a gas turbine, or the like.
[0024] The sealing system 24 includes a first seal portion 30
disposed in a groove, channel, or slot 32 formed in the stator
housing 28. For example, the first seal portion 30 may include a
retractable seal portion, such as an annular structure (e.g., an
I-shaped packing ring), which can move radially inward and outward
relative to the rotor 26 as illustrated by arrow 27. Thus, the slot
32 may have a similar annular geometry, such as an I-shaped annular
slot, along the interior of the stator housing 28. During
operation, the system can bias the first seal portion or packing
ring 30 toward the rotor 26 under certain conditions, while
retracting the packing ring 30 away from the rotor 26 into the slot
32 under other conditions. The packing ring 30 includes an
abradable structure 34 disposed on a substrate 36. The abradable
structure 34 is configured to enhance the wear resistance of the
first seal portion or packing ring 30. The abradable structure 34
may be applied by a variety of manufacturing techniques, such as
molding, diffusion bonding, brazing, thermal spraying, or
combinations thereof. The abradable structure or coating 34 may be
adaptable to various operating conditions, such as operating
temperature of the sealing system 24, rotor speed, incursion rate,
or the like.
[0025] In one embodiment, the abradable structure or coating 34 may
include an alloy of cobalt, nickel, chromium, aluminum, yttrium,
hexagonal boron nitride, and polymers such as polyesters,
polyimides, or the like. In another embodiment, the abradable
structure or coating 34 may include nickel, chromium, aluminum, and
clay (bentonite). In yet another embodiment, the abradable
structure or coating 34 may include nickel, graphite, and stainless
steel. In yet another embodiment, the abradable structure or
coating 34 may include nickel, chromium, iron, aluminum, boron and
nitrogen. In yet another embodiment, the abradable structure or
coating 34 may also include non-metallic materials (e.g.
polytetrafluoroethylene applied by electrostatic powder coating
process or polytetrafluoroethylene filled synthetic mica which may
be attached by a mechanical device). Similarly, in the other
embodiments, other compositions of the abradable structure or
coating 34 are also envisaged.
[0026] In one example, the substrate may be composed of carbon
steel, although other materials may be suitable, depending upon
such factors as the design of the machine, operating temperatures
and transients, the fluid treated (i.e., compressed), and so
forth.
[0027] In the illustrated embodiment, a retractable mechanism 37
including a plurality of biasing members 38, such as springs, are
disposed between the packing ring 30 and the stator housing 28.
Exemplary springs may include leaf springs, coil springs, helical
springs, hydraulic springs, pneumatic springs, stacked washers
provided in a housing or the like. The springs 38 are configured to
bias the packing ring 30 away from a second seal portion 40
provided on the rotor 26. The packing ring 30 is radially movable
with respect to the housing 28. In an alternate embodiment, the
retractable mechanism 37 may be provided to the first member 26.
The arrangement, number, and type of springs may be varied
depending on the application. In another exemplary embodiment, the
retractable mechanism 37 includes permanent magnets, or
electromagnets. In the illustrated embodiment, the second seal
portion 40 includes a plurality of protruding members or teeth 42
formed integrally on the rotor 26. The height of the teeth
corresponds to the maximum radial incursion of teeth 42 into the
abradable coating 34 of the packing ring 30. The abradable coating
34 typically protects packing ring 30 against possible wear due to
interference between the packing ring 30, itself, and the plurality
of teeth 42 during typical operating conditions, such as during
start-up, and transient conditions of the rotary compressor 14.
[0028] Referring to FIG. 3, a rotary machine (for example, the
rotary compressor) 14 is illustrated in accordance with certain
embodiments of the present invention. During operation of the
machine, gas enters through the suction ports and exits through the
discharge ports of the stator housing 28. The gas pressure exerted
on a top side 44 of the packing ring 30 forces the packing ring 30
against the plurality of teeth 42 provided on the rotor 26 to
maintain a minimal clearance between the packing ring 30 and the
teeth 42. In this manner, the minimized clearance improves
operational efficiency and performance of the system. For example,
during start up of the rotary compressor, the tip portions of the
plurality of teeth 42 slide over the surface of the abradable
coating 34 due to the interference between the packing ring 30 and
the teeth 42. The combined effect of centrifugal forces and the
forces resulting from biasing the packing ring 30 against the teeth
42 dislodges the particles in the abradable coating 34, causing an
incursion of the teeth 42 in the abradable coating 34. As a result,
a plurality of permanent sealing grooves 43 may be formed in the
abradable coating 34. In one example, during start-up operation of
the rotary compressor, the sealing grooves have a profile matching
as that of the teeth 42. As a result, close clearance is maintained
between the sealing elements.
[0029] During start-up, shut down, or other conditions in which gas
pressure is minimum, the springs 38 bias the packing ring 30 away
from the rotor teeth 42 ensuring preservation of the teeth 42. In
other words, a greater clearance exists between the coating 34 and
teeth 42 during a start-up stage, a shut down stage, or an idle
stage. Moreover, the greater clearance exists while the system is
not operating, such that the rotor 26 and stator housing 28 can be
separated from one another for servicing, replacement, inspection,
or other reasons.
[0030] A first stopper 46 is provided on the top side 44 of the
packing ring 30 to maintain a gas cavity between the packing ring
30 and the stator housing 28 during start-up and shut down
conditions of the machine. A plurality of second stoppers 48 are
provided on a bottom side 50 of the packing ring 30 to limit the
amount of engagement of the packing ring 30 against the plurality
of teeth 42. Thus, the stoppers 46 and 48 define a range of
movement for the first seal portion or packing ring 30. In this
manner, the packing ring 30 can move radially inward and outward
relative to the rotor 26, and specifically the plurality of teeth
42, to adjust the seal clearance during various stages of
operation.
[0031] Referring to FIG. 4, a partial cross-sectional view of a
bottom side of the abradable coating 34 facing the plurality of
teeth is illustrated. In the illustrated embodiment, the abradable
coating 34 includes a plurality of drilled holes 35 configured to
control rotor dynamics. In another exemplary embodiment, the
abradable coating 34 includes a honeycomb structure configured to
control the rotor dynamics. In other exemplary embodiments, the
coating may also include other structures configured to control
rotor dynamics response of the rotor. For example, the abradable
structure or coating 34 may include a plurality of layers of
different materials, different porosities/solidities, different
hardnesses, different wear properties, different thermal properties
(e.g., coefficients of thermal expansion), different thicknesses,
different frictional properties, or combinations thereof In one
example, the abradable structure or coating 34 may include a
plurality of concentric rings. The abradable coating in accordance
with aspects of the present invention provides a high strength to
weight ratio and a stiffer, stable coating. The cavity of the
drilled holes in the honeycomb structure provide pneumatic damping
to control rotor dynamics.
[0032] Referring to FIG. 5, a diagrammatical axial view of the
sealing system 24 is illustrated. In the illustrated embodiment, as
discussed previously, the rotor 26 (located at the center) is
disposed inside the stator housing 28. The I-shaped packing ring 30
is disposed in the slot formed in the stator housing 28. The
packing ring 30 includes the abradable coating 34 provided on the
substrate 36. The spring 38 is disposed between the packing ring 30
and the stator housing 28. The spring 38 is configured to bias the
packing ring 30 away from plurality of teeth 42 provided on the
rotor 26. In the illustrated embodiment, the position of only one
of the plurality of springs 38 is illustrated for simplicity.
Although one packing ring 30 is illustrated in FIG. 4, the system
may include multiple packing rings 30 disposed between the rotor 26
and the stator housing 28. Similarly, multiple springs 38 may be
disposed between each packing ring 30 and the stator housing 28. As
mentioned previously, the first stopper 46 is provided on the top
side of the packing ring 30 to maintain a gas cavity between the
packing ring 30 and the stator housing 28 during start-up and shut
down conditions of the machine. The second stopper 48 is provided
on the bottom side of the packing ring 30 to limit the amount of
engagement of the packing ring 30 against the plurality of teeth
42.
[0033] Referring to FIG. 6, another embodiment of the sealing
system 24 is illustrated in accordance with aspects of the present
invention. As mentioned in previous embodiments, the sealing system
24 is disposed between the rotor 26 and the stator housing 28. The
sealing system 24 includes the packing ring 30 disposed in the slot
32 formed in the stator housing 28. In the illustrated embodiment,
the second seal portion 40 includes a plurality of teeth 51 (e.g.
"J" strip type) detachably fitted to a plurality of annular
grooves, channels, or slots 52 formed in the rotor 26. A plurality
of wires 54 (e.g., ring-shaped wires) may be used to hold the
plurality of teeth 51 in the slots 52 formed in the rotor 26. The
plurality of teeth 51 protrudes radially outwards to the packing
ring 30. As discussed in previous embodiments, the springs 38 are
configured to bias the packing ring 30 away from tip portions of
the plurality of teeth 51 fitted to the slots 52 formed in the
rotor 26. The illustrated example provides the additional advantage
that the plurality of teeth 51 may be replaced if the plurality of
teeth 51 are damaged or worn due to interference, due to the fact
that the plurality of teeth 51 are detachably fitted to the rotor
26.
[0034] Referring to FIG. 7, another embodiment of the sealing
system 24 is illustrated in accordance with aspects of the present
invention. The sealing system 24 is disposed between the rotor 26
and the stator housing 28. The sealing system 24 includes the
packing ring 30 disposed in the slot 32 formed in the stator
housing 28. In this exemplary embodiment, the plurality of teeth 42
are provided on the packing ring 30 rather than the rotor 26, while
the abradable structure or coating 34 is provided on the rotor 26
rather than the ring 30. The plurality of biasing members 38, such
as springs, are disposed between the packing ring 30 and the stator
housing 28. The springs 38, as mentioned previously, are configured
to bias the packing ring 30 away from the second seal portion 40
provided on the rotor 26. In the illustrated embodiment, the second
seal portion 40 includes the abradable coating 34 provided on the
rotor 26. During start-up and shut down of the machine, the springs
38 bias the packing ring 30 having the plurality of teeth 42 away
from the abradable coating 34 provided on the rotor 26. During
operation of the machine, the operating gas pressure pushes the
packing ring 30 against the abradable coating 34 provided on the
rotor 26 to maintain minimal clearance and reduce gas leakage. As
discussed previously, during start up of the rotary compressor, the
tip portions of the plurality of teeth 42 slide over the surface of
the abradable coating 34 due to the interference between the
packing ring 30 and the abradable coating 34. The combined effect
of centrifugal forces and the forces resulting from biasing the
packing ring 30 against the abradable coating 34 dislodges the
particles in the abradable coating 34, causing an incursion of the
teeth 42 in the abradable coating 34.
[0035] In yet another embodiment similar to the embodiment
illustrated in FIG. 6, a plurality of teeth may be detachably
fitted to slots formed in the packing ring 30. The plurality of
teeth protrudes downwards to a surface of the rotor 26. For
example, the teeth may engage the rotor 26 at an annularly raised
surface, an annularly recessed surface, or a combination thereof.
Flow of fluid is throttled at locations where the teeth are
provided on the packing ring 30. The raised and/or recessed surface
of the rotor 26 also functions to divert fluid flow along a radial
direction providing a more tortuous path relative to the rotor
26.
[0036] Referring to FIG. 8, this drawing illustrates an exemplary
system, such as a steam turbine 56, in accordance with certain
embodiments of the present invention. The steam turbine 56 includes
a rotating turbine bucket 58 disposed in a stationary turbine
housing 60. A retractable abradable sealing system 62 is disposed
between the rotating turbine bucket 58 and the stationary turbine
housing 60. The sealing system 62 includes a packing ring 64
disposed in a slot 66 provided in the stationary turbine housing
60. The packing ring 64 is also disposed adjacent to the turbine
bucket 58, separating pressure regions on axially opposite sides of
the packing ring 64. The packing ring 64 includes an abradable
structure or coating 67 provided on a substrate 68. The coating 67
is provided facing a plurality of radial projections 70 and grooves
72 provided on the turbine bucket 58. The abradable coating 67 is
of a design for obtaining close clearances with the radial
projections and grooves provided on the turbine bucket 58. In
certain embodiments, the abradable structure or coating 67 may have
a geometry at least partially matched with the geometry of the
projections 70 and grooves 72. In other words, the abradable
structure or coating 67 may have recesses corresponding to the
projections 70 and extensions corresponding to the grooves 72. In
this manner, the abradable structure or coating 67 may provide a
labyrinth type seal in addition to the wear properties and
clearance adjustment characteristics discussed in detail above.
These mating geometrical structures also may be withdrawn out of
engagement with one another during non-operational conditions, such
that the turbine bucket 58 and the housing 60 can be separated from
one another for servicing, maintenance, inspection, replacement,
and so forth.
[0037] In the illustrated embodiment of FIG. 8, a retractable
mechanism 74 including a plurality of biasing members 76, such as
springs, are disposed between the packing ring 64 and the
stationary turbine housing 60. The springs 76 are configured to
bias the packing ring 64 away from the projections 70 and grooves
72 provided on the turbine bucket 58. The packing ring 64 is
radially movable with respect to the housing 60 as indicated by
arrow 69. The abradable coating 67 generally protects packing ring
64 against possible wear due to interference between the packing
ring 64, itself, and the plurality of projections 70 during typical
operating conditions, such as during start-up, and transient
conditions of the steam turbine 56.
[0038] During operation of the steam turbine, gas enters through
the suction ports and exits through the discharge ports of the
stationary turbine housing 60. The gas pressure exerted on a top
side of the packing ring 64 forces the packing ring 64 against the
plurality of projections 70 provided on the turbine bucket 58 to
maintain a minimal clearance between the packing ring 64 and the
projections 70. In this manner, the minimized clearance improves
operational efficiency and performance of the system.
[0039] During start-up, shut down, or other conditions in which gas
pressure is minimum, the springs 76 bias the packing ring 64 away
from the projections 70 ensuring preservation of the projections
70. In other words, a greater clearance exists between the coating
67 and projections 70 during a start-up stage, a shut down stage,
or an idle stage. Moreover, the greater clearance exists while the
system is not operating, such that the rotating turbine bucket 58
and stationary turbine housing 60 can be separated from one another
for servicing, replacement, inspection, or other reasons.
[0040] A first stopper 78 is provided on the top side of the
packing ring 64 to maintain a gas cavity between the packing ring
64 and the stationary turbine housing 60 during start-up and shut
down conditions of the steam turbine 56. A plurality of second
stoppers 80 are provided on a bottom side of the packing ring 64 to
limit the amount of engagement of the packing ring 64 against the
plurality of projections 70. Thus, the stoppers 78 and 80 define a
range of movement for the packing ring 64. In this manner, the
packing ring 64 can move radially inward and outward relative to
the rotating turbine bucket 58, and specifically the plurality of
projections 70, to adjust the seal clearance during various stages
of operation.
[0041] Referring to FIG. 9, a flow chart illustrating exemplary
steps involved in method of operating a rotary machine (example,
rotary compressor) is illustrated. In accordance with the
illustrated exemplary embodiment, the method includes rotating the
first member relative to the second member, or the second member
relative to the first member as represented by step 82. In one
example, the first member comprises the rotor and the second member
comprises the stator housing. The sealing system is disposed
between the first member and the second member. The sealing system
includes the first seal portion disposed in a groove, channel, or
slot formed in the second member. For example, the first seal
portion may include the I-shaped packing ring, which can move
radially inward and outward relative to the second member. The
packing ring includes the abradable structure disposed on the
substrate.
[0042] During operation of the machine, gas enters through the
suction ports and exits through the discharge ports of the second
member. The gas pressure exerted on the top side of the first seal
portion forces the first seal portion against the second seal
portion (i.e. plurality of teeth) provided on the first member to
maintain a minimal clearance between the first seal portion and the
second seal portion as represented by step 84. During start up of
the rotary compressor, the tip portions of the plurality of teeth
slide over the surface of the abradable coating due to the
interference between the packing ring and the teeth. The combined
effect of centrifugal forces and the forces resulting from biasing
the packing ring against the teeth dislodges the particles in the
abradable coating, causing an incursion of the teeth in the
abradable coating. As a result, a plurality of permanent sealing
grooves may be formed in the abradable coating. The sealing grooves
may have a profile matching as that of the teeth. As a result,
close clearance is maintained between the sealing elements.
[0043] During start-up, shut down, or other conditions in which gas
pressure is minimum, the springs bias the first seal portion away
from the second seal portion ensuring preservation of the first
seal portion and the second seal portion. The first stopper
provided on the top side of the first seal portion facilitates to
maintain a gas cavity between the first seal portion and the second
member during start-up and shut down conditions of the machine. The
plurality of second stoppers provided on the bottom side of the
first seal portion facilitates to limit the amount of engagement of
the first seal portion against the second seal portion as
represented by step 86. During operation of the machine, the first
seal portion engages the second seal portion provided on the first
member to provide a zero-clearance labyrinth seal between the first
member and the second member as represented by step 88.
[0044] Referring to FIG. 10, a flow chart illustrating exemplary
steps involved in a method of manufacturing the rotary machine
(example, rotary compressor) is illustrated. In accordance with the
illustrated exemplary embodiment, the method includes disposing the
retractable abradable sealing system between the first member and
the second member configured to control the leakage of fluid
between the first member and the second member as represented by
step 90. In one example, the first member comprises the rotor and
the second member comprises the stator housing. The sealing system
24 includes the first seal portion (e.g., I-shaped packing ring),
disposed in the slot formed in the stator housing. The packing ring
includes the abradable structure (e.g. abradable coating) provided
on the substrate.
[0045] The method includes disposing the retractable mechanism in
the second member (packing ring) as represented by step 92. In the
illustrated embodiment, the retractable mechanism including the
plurality of biasing members, such as springs, are disposed between
the first seal portion and the second seal portion as represented
by step 94. The springs are configured to bias the first seal
portion away from the second seal portion provided on the rotor.
The first seal portion is radially movable with respect to the
second member. The method further includes disposing the second
seal portion (one or more sealing teeth) on the first member in
such a way so as to mate with the first seal portion to provide a
zero-clearance labyrinth seal during operation of the machine as
represented by step 96.
[0046] 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.
* * * * *