Abstract:
An actuated seal assembly for controlling flow in a fluid path in turbomachinery comprising a seal and a seal carrier coupled to the seal is provided. A displacement apparatus is coupled to the seal carrier for positioning the seal so as to control the flow in the fluid path. In addition, a drive system is provided for powering the displacement apparatus.

Description:
BACKGROUND OF INVENTION 
     The present invention relates generally to rotary machines, and more particularly to an actuated seal for a rotary machine such as steam and gas turbines. 
     Rotary machines include, without limitation, turbines for steam turbines and compressors and turbines for gas turbines. A steam turbine has a steam path that typically includes, in serial-flow relationship, a steam inlet, a turbine, and a steam outlet. A gas turbine has a gas path which typically includes, in serial-flow relationship, an air intake (or inlet), a compressor, a combustor, a turbine, and a gas outlet (or exhaust nozzle). Gas or steam leakage, either out of the gas or steam path or into the gas or steam path, from an area of higher pressure to an area of lower pressure, is generally undesirable. For example, a gas path leakage in the turbine or compressor area of a gas turbine, between the rotor of the turbine or compressor and the circumferentially surrounding turbine or compressor casing, will lower the efficiency of the gas turbine leading to increased fuel costs. Also, steam-path leakage in the turbine area of a steam turbine, between the rotor of the turbine and the circumferentially surrounding casing, will lower the efficiency of the steam turbine leading to increased fuel costs. 
     It is known in the art of steam turbines to position, singly or in combination, variable clearance labyrinth-seal segments and brush seals in a circumferential array between the rotor of the turbine and the circumferentially surrounding casing to minimize steam-path leakage. Springs hold the segments radially inward against surfaces on the casing that establish radial clearance between seal and rotor but allow segments to move radially outward in the event of rotor contact. While labyrinth seals, singly or in combination with brush seals, have proved to be quite reliable, their performance degrades over time as a result of transient events in which the stationary and rotating components interfere, rubbing the labyrinth teeth into a “mushroom” profile and opening the seal clearance. 
     Accordingly, there is a need in the art for a rotary machine having good leakage control between stationary and rotating components. 
     SUMMARY OF INVENTION 
     The present invention provides an actuated seal assembly for controlling flow in a fluid path in turbomachinery comprising a seal and a seal carrier coupled to the seal. A displacement apparatus is coupled to the seal carrier for positioning the seal so as to control the flow in the fluid path. In addition, a drive system is provided for powering the displacement apparatus. 
    
    
     BRIEF DESCRIPTION OF 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 schematic, cross-sectional exploded view of an actuated seal comprising a labyrinth seal having a seal carrier disposed therein in accordance with the present invention; 
     FIG. 2 is a schematic, cross-sectional exploded view of an actuated seal comprising a seal carrier disposed in a housing; 
     FIG. 3 is a schematic, cross-sectional exploded view of another embodiment of the instant invention; 
     FIG. 4 is a schematic, cross-sectional exploded view of another embodiment of the instant invention; 
     FIG. 5 is a schematic, cross-sectional exploded view of another embodiment of the instant invention; 
     FIG. 6 is a schematic, cross-sectional exploded view of another embodiment of the instant invention; 
     FIG. 7 is a schematic, cross-sectional exploded view of another embodiment of the instant invention; 
     FIG. 8 is a schematic, cross-sectional exploded view of another embodiment of the instant invention; 
     FIG. 9 shows a block diagram (e.g. flow chart) of the instant invention; 
     FIG. 10 is a schematic, cross-sectional exploded view of another embodiment of the instant invention; 
     FIG. 11 is a schematic, cross-sectional exploded view of another embodiment of the instant invention; 
     FIG. 12 is a schematic view of an actuating mechanism comprising lifting buttons disposed in respective cavities in accordance with the present invention; 
     FIG. 13 is a schematic, cross-sectional exploded view of an actuating mechanism comprising a lifting button disposed in a cavity; 
     FIG. 14 is a schematic, cross-sectional exploded view of another embodiment of the instant invention; and 
     FIG. 15 is a schematic, cross-sectional exploded view of another embodiment of the instant invention. 
    
    
     DETAILED DESCRIPTION 
     An actuated seal assembly, generally designated  100 , disposed between a rotating member  110 , for example a rotor, and a stationary turbine housing  120 , comprises an arcuate seal carrier  130  disposed adjacent to rotating member  110  separating pressure regions on axially opposite sides of arcuate seal carrier  130  (see FIG.  1 ). FIG. 1 shows a labyrinth seal  135  having an arcuate seal carrier  130  disposed therein. Seal carrier  130  typically comprises, but is not limited to, at least one seal  140 , for example, at least one brush seal bristle, coupled to the seal carrier  130  and a displacement apparatus  150  coupled to the seal carrier  130 . It will be appreciated that displacement apparatus  150  typically comprises an actuator, a return device or a combination thereof. In an alternative embodiment, displacement apparatus  150  is coupled to the labyrinth seal top portion  190 , or alternatively, the labyrinth seal bottom portion  200 . In addition, a drive system  160 , for example, is used to power displacement apparatus  150 . 
     These components form part of a turbine in which a flowing fluid medium in a fluid path, for example, gas or steam, is passed between the rotating member  110  and housing  120 . In an alternative embodiment, fluid medium typically comprises a liquid. It will be appreciated, however, that fluid path flows from the high pressure side towards the low pressure side, i.e., from the left to right of drawing FIG.  1 . In operation, displacement apparatus  150  actuates the seal carrier  130 , or alternatively the labyrinth seal  135 , to either lift off or to adjust seal carrier  130  position during operation or during transient events, for example, during startup and shutdown. It will be appreciated that seal carrier  130  and at least one seal  140  is typically either internally or externally adjustable depending on the application. That is, actuated seal assembly  100  is located internal or external to the turbine and adjusts seal carrier  130  and accompanying seal  140  from such respective location. As a result, the life of the seal  140  (e.g. bristles) is extended by actuating the seal carrier  130  before bristles or seal carrier  130  rub against rotating member  110 . The life and performance of the brush seal bristles, singly or in combination with other seals, for example, is increased due to the fact that the bristles are not continuously rubbing at high speed which causes the bristles to reach a melting temperature or cause excessive wear. In addition, the performance of labyrinth teeth seals  135 , singly or in combination with other seals, for example, does not degrade over time because the teeth are less prone to be rubbed into a “mushroom” profile thus maintaining an optimal seal clearance between labyrinth seal  135  and rotating member  110 . 
     The drive system  160  typically comprises a motor, a pump, an electric power supply or the like. The motor typically comprises a linear motor, rotary motor or the like. In one embodiment, such motor is typically coupled to the displacement apparatus  150  by gears, cables, wires, pulleys or the like. The pump typically comprises a gas pump, water pump, hydraulic pump or the like and the electric power supply typically comprises a piezoelectric device or the like. It will be appreciated that drive system  160  is typically manually or electrically actuated and that the position of the drive system  160  is typically internal or external to actuated seal  100 . 
     In one embodiment, the seal carrier  130 , singly or in combination, typically comprises at least one seal  140 , for example, at least one brush seal bristle. It will be appreciated that other seals  140  typically include, but are not limited to, labyrinth seals, abradable seals, honeycomb seals, leaf seals, finger seals, ceramic seals, aramid seals, aspirating seals and combinations thereof. It will be appreciated that seal carrier  130  is typically combined with a labyrinth seal carrier having the aforementioned components, singly or in any combination thereof (not shown). The displacement apparatus  150  typically comprises, but is not limited to, at least one displacement device such as a spring, bellows, inflatable tube, rod, cam, hydraulic cylinder, pneumatic device, piezoelectric device, wire, cable, bimetallic material, phase changing material, solenoid, or combinations thereof. It will be appreciated that the displacement apparatus  150  typically works in conjunction with at least one spring  165  to return seal carrier  130  to its initial position. 
     In one embodiment, the rod, for example, is positioned directly between seal carrier bottom portion  170  and labyrinth channel  175 . In an alternative embodiment, the rod is positioned directly between seal carrier top portion  180  and labyrinth channel  175 . Here, the drive system  160 , coupled to the displacement apparatus  150  by a screw, for example, actuates the rod to raise or adjust seal carrier  130 . It will be appreciated by one of ordinary skill in the art that the drive system  160  is typically bi-directional so as to allow the actuated rod to lift, lower or adjust the seal carrier  130  during operation. In another embodiment, the rod is typically positioned directly between seal carrier top portion  180  and housing  120  (see FIG.  2 ). In an alternative embodiment, the rod is typically positioned directly between seal carrier bottom portion  170  and housing  120 . In addition, the aforementioned embodiments typically comprise least one spring  165  disposed between seal carrier bottom portion  170  and housing  120 , seal carrier top portion  180  and housing  120 , seal carrier bottom portion  170  and labyrinth channel  175 , and seal carrier top portion  180  and labyrinth channel  175 . In FIG. 2, the spring  165  provides a constant outward radial force keeping the seal  140  of seal carrier  130  from touching rotating member  110 . In operation, the rod is actuated by the drive system  160  to lower or adjust seal carrier  130  and respective seal  140  with respect to rotating member  110 . In a further embodiment, a spring-loaded rod is typically positioned between seal carrier bottom portion  170  and housing  120  (see FIG.  3 ). Here, the drive system  160 , coupled to the spring-loaded rod by a wire, for example, actuates the spring-loaded rod so as to raise, lower or adjust the seal carrier  130  with respect to the rotating member  110 . Alternatively, it will also be appreciated that the spring-loaded rod is typically positioned between seal carrier top portion  180  and housing  120  to perform the same functions discussed above. The rod, in any embodiment discussed herein, is typically tapered or formed so as to allow ease of penetration between seal carrier top or bottom portions  170 ,  180  and housing  120 . 
     In another embodiment, a wire  195  or cable, for example, is coupled to seal carrier  130  to force seal carrier  130  radially inwardly or radially outwardly (see FIG.  4 ). Here, the drive system  160  is coupled to a wire spool  185 , for example, to actuate the seal carrier  130  radially inwardly or radially outwardly depending upon the configuration of the wire on the seal carrier segment. As used herein, “on”, “in”, “over”, “above”, “under” and the like are used to refer to the relative location of elements of actuated seal  100  as illustrated in the Figures and is not meant to be a limitation in any manner with respect to the orientation or operation of actuated seal  100 . In operation, the wire spool  185  is rotated clockwise or counterclockwise, for example, so as to radially inwardly move seal carrier  130  or radially outwardly move seal carrier  130 . For illustrative purposes herein, when the wire spool  185  is rotated clockwise by drive system  160 , for example, the wire  195  circumference is decreased thereby reducing the radial distance between seal carrier  130  and rotating member  110 . When the wire spool  185  is rotated counterclockwise by drive system  160 , for example, the wire  195  circumference is increased thereby increased the radial distance between seal carrier  130  and rotating member  110 . It will be appreciated that at least one spring  165  is typically located on seal carrier bottom portion  170  so as to provide an opposing radial force when the wire spool  185  is rotated clockwise. In addition, the position of at least one spring  165  on seal carrier bottom portion  170  allows seal carrier  130  to move radially outward when the wire spool  185  is rotated counterclockwise. In addition, at least one spring  165  is typically located on seal carrier top portion  180  so as to provide an opposing radial force when wire spool  185  is rotated counterclockwise, for example. It will be appreciated that at least one wire  195  or cable, for example, is typically coupled to at least one seal carrier  130 , a plurality of seal carriers  130  or all of the seal carriers  130  in actuated seal  100 . 
     In another embodiment, the drive system  160 , for example an electric power supply, is coupled to the displacement apparatus  150  which is coupled to seal carrier  130  (see FIG.  5 ). Here, the displacement apparatus  150  typically comprises, singly or in combination, at least one operating device such as a piezoelectric device, electromagnetic device, phase changing material, bimetallic material, electric heater, and the like. In operation, drive system  160  actuates the displacement apparatus  150  to force seal carrier  130  radially with respect to rotating member  110 . It will be appreciated that at least one displacement apparatus  150  is typically coupled to at least one seal carrier  130 , a plurality of seal carriers  130  or all of the seal carriers  130  in actuated seal  100 . 
     In another embodiment, the displacement apparatus  150 , for example, at least one elongated tube (see FIG.  6 ), at least one bellows (see FIG. 7) or a combination thereof, is disposed between seal carrier bottom portion  170  and housing  120 . In an alternative embodiment, the displacement apparatus  150  is disposed between seal carrier top portion  180  and housing  120 . In operation, the tube or bellows is inflated to radially outwardly move seal carrier  130  and accompanying bristles  140  from rotating member  110 . In an alternative embodiment, the tube or bellows (disposed between seal carrier top portion  180  and housing  120 ) is inflated to radially inwardly move seal carrier  130  and accompanying bristles towards housing  120 . In this embodiment, it will be appreciated that before displacement apparatus  150  is actuated and at least one spring  165  is typically disposed between seal carrier top portion  180  and housing  120  so as to radially inwardly force seal carrier  130  and accompanying seal  140  toward rotating member  110 . Alternatively, at least one spring  165  is typically disposed between seal carrier bottom portion  170  and housing  120  so as to radially outwardly force seal carrier  130  and accompanying seal  140  from rotating member  110 . It will be appreciated that at least one tube or bellows, for example, is typically coupled to at least one seal carrier  130 , a plurality of seal carriers  130  or all of the seal carriers  130  in actuated seal  100 . 
     In another embodiment, actuated seal assembly  100  comprises a labyrinth seal  135  having seal carrier  130  disposed therein (see FIG.  8 ). In this embodiment, the displacement apparatus  150 , for example, at least one elongated tube, at least one bellows or any combination thereof, is disposed between seal carrier bottom portion  170  and labyrinth channel  175 . In addition, displacement apparatus  150  is disposed between labyrinth seal bottom portion  200  and housing  120 . It will be appreciated that displacement apparatus  150  location in combination with a spring  165  is typically varied. For example, displacement apparatus  150  is typically disposed between seal carrier top portion  180  and labyrinth channel  175 , disposed between labyrinth seal top portion  190  and housing  120 , or in any combination with the aforementioned embodiments. 
     A smart seal system  500  is shown in FIG. 9. A “smart seal system”, as used herein, refers to a system in which there is some manner of automated control of the distance between seal  140  and rotating member  110 . In one embodiment which represents remotely controlling the seal system  500 , a control processor  510  receives a control property measurement  520  and generates a drive system command  530 . At least one seal communications interface  540  receives the drive system command  530 , a controllable property signal  630  and generates the control property measurement  520 . Seal communications interface  540  typically comprises wireless, wired communication modalities, electrical, optical, or other means of communicating the necessary signals with the desired speed and reliability. For example, seal communications interface  540  typically comprises, but is not limited to, a communication system such as a geo-synchronous L-band satellite system, a low earth orbit satellite system, a two-way paging system, a modem connection or any communication system capable of explicitly effecting communication between the control processor  510  and drive system  160  and between control processor  510  and property sensor  610 . It will be appreciated that seal communications interface  540  comprises any apparatus that achieves translation between the signal formats compatible with the drive system  160 , property sensor  610  and that of the control processor  510 . Examples of such signal formats include, but are not limited to, parallel binary, serial binary and radio frequency communication. In an alternative embodiment which represents on-site control of the seal system  500 , the control processor  510  receives controllable property signal  630 . In addition, drive system  160  receives drive system signal  560  from the control processor  510  (see FIG.  11 ). Referring now to FIG. 10, the seal communications interface  540  transmits the control property measurement  520  and a drive system signal  560  in correspondance to the controllable property signal  630  and the drive system command  530 , respectively. For example, if the seal communications interface  540  is a radio transceiver, and the controllable property signal  520  comprises an analog voltage signal encoding, for example, the temperature of the fluid path  600 , then control property measurement  520  typically comprises an electromagnetic wave modulated to carry the same information as the controllable property signal  520 . It will be appreciated that controllable property  620  typically includes, but is not limited to, temperature, pressure, relative position between seal  140  and rotating member  110  and the rotational speed of rotating member  110  (see FIG.  1 ). A drive system  170  receives the drive system signal  560  and generates motive effort  580  (see FIG.  10 ). “Motive effort,” as used herein, typically means the generation of a force, a torque, a pressure, a heat, an electric charge or anything that causes a seal assembly  590  to move. As a result, seal assembly  590  responds to motive effort  580  so as to regulate flow in a fluid path  600 . In addition, a property sensor  610  senses the controllable property  620  of the flow in the fluid path  600  and generates the controllable property signal  630  which is subsequently received by the seal communications interface  540 . 
     In operation (see FIG.  10 ), for example, property sensor  610  is disposed on seal carrier  130 . It will be appreciated that the at least one property sensor  610  is typically used and the location of property sensor  610  is not limited to seal carrier  130 . In addition, it will be appreciated that the embodiment used in this example is meant to be used only for illustrative purposes and not meant to be a limitation to the present invention. Here, property sensor  610  detects at least one controllable property  620  of the flow in a fluid path  600 , for example, the temperature of the flow in the fluid path  600  in the turbine, and generates a controllable property signal  630 . The controllable property signal  630  is received by the seal communications interface  540  and is transformed to a control property measurement  520  which is subsequently received by the control processor  510 , for example, from a voltage to a radio frequency (RF) signal. Here, control processor  510  sends a drive system command  530  signal, where such command signal is translated by the seal communications interface  540 , and is subsequently translated to a drive system signal  560 . Drive system signal  560  typically comprises command information so as to allow the drive system  160  to control the gap of the fluid path  600  defined between seal  140  and rotating member  110 , for example. It will be appreciated that the drive system  160 , singly or in combination with a displacement apparatus  150 , generates motive effort to adjust seal assembly  590  according to the drive system signal  560 . For example, the control processor  510  is typically informed that the flow in the fluid path  600  is at a certain temperature and hence send a command, via a drive system signal  560 , to the drive system  160  indicating an outwardly or inwardly radial adjustment of seal assembly  590  so as to control such temperature. 
     In another embodiment, an actuating mechanism, generally designated  700 , typically comprises a housing  710  having at least one lifting button  740  disposed therein (see FIG.  12 ). A channel  730  is disposed in fluid communication with at least one cavity  720  and the lifting button  740  is disposed within the cavity  720  so that the button  740  is movable between a retracted position and a extended position upon introduction of a pressurized medium, for example a gas source or steam source located internally or externally to a turbine. (see FIG.  13 ). In an alternative embodiment, the pressurized medium is a liquid. In another embodiment, actuating mechanism  700  comprises at least one washer  830  concentrically disposed about the cavity  720  so as to restrict particulates from entering areas between lifting button  740  and housing  710 . “Concentrically,” as used herein, means that that washer  830  and cavity  720  are disposed in relation to each other so as to have a common axis. In addition, a compliant mechanism  840 , for example a bellows, is secured to the washer  830  and lifting button  740  so as to allow compliant mechanism  840  to be radially displaced upon introduction of the pressurized medium and subsequently move seal carrier  770  radially. “Compliant,” as used herein, means that the structure of the compliant mechanism  840  yields under a force or pressure, for example. In another embodiment, actuating mechanism  700  is disposed in a turbine where actuating mechanism  700  is placed between a rotating member  750 , for example a rotor, and a stationary housing, for example a turbine housing  760  (see FIG.  14 ). Turbine housing  760  typically comprises an arcuate seal carrier  770  disposed adjacent to the rotating member  750  so as to separate pressure regions on axially opposite sides of seal carrier  770 . In another embodiment, seal carrier  770  is disposed in a labyrinth seal (not shown). Seal carrier  770  typically comprises, but is not limited to, at least one seal  780 , for example, at least one brush seal bristle, disposed in seal carrier  730 . In addition, actuating mechanism  700  is coupled to a seal carrier top portion  790 , coupled to the seal carrier bottom portion  800  and alternatively, a respective actuating mechanism  700  is disposed on seal carrier top portion  790  and seal carrier bottom portion  800  as discussed hereinafter. 
     In another embodiment, these components form part of a turbine in which a flowing fluid medium in a fluid path  810 , for example, gas or steam, is passed between the rotating member  750  and turbine housing  760 . For example, fluid path  810  flows from the high pressure side, designated “Phi”, towards the low pressure side, designated “Plow”, i.e., from the left to right of drawing FIG.  14 . For illustrative purposes, FIG. 14 shows seal carrier  770  and accompanying seal  780  in a fully closed position and FIG. 15 shows seal carrier  770  and accompanying seal  780  in a fully open position. It will be appreciated that seal carrier and accompanying seal  780  are movable between the fully closed (see FIG. 14) and the fully open position (see FIG.  15 ). As seal carrier  770  and accompanying seal  780  are moved from the fully open position to the fully closed position (see FIG.  14 ), the flow in a fluid path  810  is restricted between seal  780  and rotating member  750 . It will be appreciated that a throttling function occurs as seal carrier  770  moves towards the closed position due to the reduction of the cross-sectional area of the gap defined between seal  780  and rotating member  750  thereby causing reduced fluid flow therebetween. In addition, seal carrier  770  typically includes, but is not limited to, at least one gasket (not shown) consisting essentially of an o-ring, c-seal and w-seal so as to provide a seal between seal carrier  770  and labyrinth seal (not shown) or alternatively, seal carrier  770  and turbine housing  760 . 
     In operation, actuating mechanism  700  actuates seal carrier  770 , or alternatively labyrinth seal (not shown), to lift, lower or adjust seal carrier  770  position during operation or during transient events, for example, during startup and shutdown. In one embodiment, when the pressurized medium is introduced into channel  730 , a pressure load, designated “F”, forces seal carrier  770  radially upward resulting in lifting seal  780  away from rotating member  750  (see FIG.  15 ). As a result, actuating mechanism  700  acts to open a fluid path gap, designated “G”, between the high and low pressure areas on axially opposite sides of the seal  780  and control the flow in the fluid path  810  between rotating member  750  and turbine housing  760 . Alternatively, pressurized load “F” forces seal carrier  770  radially downward and keeps seal  780  disposed against rotating member  750 . 
     In a further embodiment, actuating mechanism  700  is coupled to the seal carrier top portion  790 , coupled to the seal carrier bottom portion  800  and alternatively, a respective actuating mechanism  700  is disposed on seal carrier top portion  790  and seal carrier bottom portion  800 . In operation, actuating mechanism  700  acts to raise, lower or adjust seal carrier  770  and respective seal  780  with respect to rotating member  750 . In another embodiment, actuating mechanism works in conjunction with at least one spring  820  to return seal carrier  770  to its initial position. For example, the spring  820  is located between seal carrier bottom portion  800  and turbine housing  760  so as to provide a constant outward radial force on seal carrier  770  and keep seal  780  from touching rotating member  750 . In a further embodiment, it will be appreciated that spring  820  is located between seal carrier top portion  790  and turbine housing  760  (see FIG.  15 ). 
     In operation, a method of retrofitting actuating mechanism  700  in a turbine wherein actuating mechanism  700  comprises a seal carrier  770  disposed therein, comprises placing actuating mechanism  700  adjacent to seal carrier  770  such that seal carrier  770  is moved radially in correspondance with the position of lifting button  740  assembly on said actuating mechanism  700 . In addition, actuating mechanism  700  comprises a housing  710  having at least one cavity  720  and a channel  730  disposed within the housing  710  in flow communication with cavity  720 . The lifting button  740  assembly is disposed within the cavity  720  and is movable between a retracted position and an extended position in correspondence with the pressure in the cavity  720 . One advantage to such method of retrofitting is that the actuating mechanism  700  in turbine may simply be removed and replaced with another actuating mechanism  700  thereby reducing down time of the turbine. In some operations, such method of retrofitting allows a technician to replace actuating mechanism without having to disassemble any major parts in the turbine thereby reducing repair costs. 
     It will be apparent to those skilled in the art that, while the invention has been illustrated and described herein in accordance with the patent statutes, modification and changes may be made in the disclosed embodiments without departing from the true spirit and scope of the invention. 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.