US20070248452A1

US20070248452A1 - Retractable compliant abradable sealing system and method for rotary machines

Info

Publication number: US20070248452A1
Application number: US11/411,184
Authority: US
Inventors: Bruce Brisson; Christopher Wolfe; Kripa Varanasi
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 2006-04-25
Filing date: 2006-04-25
Publication date: 2007-10-25

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.

Description

BACKGROUND

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.
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.
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

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.
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.
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.
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

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:
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;
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;
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;
FIG. 4 is a cross sectional view of an abradable coating having drilled holes in accordance with aspects of FIG. 2;
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;
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;
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;
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;
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
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

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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.

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.