Abstract:
A method for assembling a rotary machine is provided. The method includes providing at least one seal assembly that includes at least one annular seal housing defined by a top wall, a front wall, and a rear wall, that are connected together such that a cavity is defined within the housing, coupling a plurality of flexible plates within the cavity such that the plates are axially-spaced from the front wall and the rear wall within the cavity, coupling at least one side plate to the at least one annular seal housing such that the at least one side plate is moveable with respect the front wall and the rear wall, and coupling the at least one sealing assembly within a rotary machine to facilitate sealing between a rotary component and a stator component.

Description:
BACKGROUND OF THE INVENTION 
     This application relates generally to rotary machines and more particularly, to methods and apparatus for sealing rotary machines. 
     At least some known rotary machines such as, but not limited to steam turbines or gas turbines, include a plurality of seal assemblies in a fluid flow path to facilitate increasing the operating efficiency of the rotary machine. For example, some known seal assemblies are coupled between a stationary component and a rotary component to provide sealing between a high-pressure area and a low-pressure area. Moreover, to facilitate thrust balancing, a turbine rotor may be sealed relative to a cooperating stator to facilitate maintaining a higher pressure in a forward portion of the rotor as compared to a lower pressure in an aft portion of the rotor. 
     At least some known seal assemblies include seal members such as, but not limited to, brush seals, labyrinth seals, and/or compliant plate seals. Compliant plate seals generally include a plurality of compliant plates such as, but not limited to, leaf seals, shingles seals, tapered plate seals, laby-plate seals, and/or intermediate plate seals, that are oriented in a pack extending circumferentially about a central rotational axis of a rotary component. More specifically, the plates are oriented such that a tip of each plate contacts the rotor or rotary component during various operating conditions of the rotary machine. For example, during shut down of the turbine engine, a portion of the plates are generally in contact with a rotary component. During rotation of the rotary component, various forces such as compliant plate/rotor contact forces, hydrodynamic lifting forces, and differential pressure forces cause the plates to deflect upward. Compliant plate/rotor contact forces are generated as a result of contact between the compliant plate and the rotary component. Hydrodynamic lifting forces are generated by rotation of the rotary component. Differential pressure forces include radially outward lifting forces and radially inward blow-down forces that are generated due to the static pressure distribution on the compliant plates. A balance between preventing contact between the compliant plate tips and the rotor, and preventing seal leakage is desirable to increase the life-span of the compliant plates and to increase the efficiency of the rotary machine. 
     Some known seal assemblies include a seal housing that includes a high-pressure-side front wall and a low-pressure-side rear wall that is spaced a distance from the front wall such that a cavity is defined therebetween. In such seal assemblies, the gap between the compliant plates and the front wall, and the gap between the compliant plates and the rear wall, are each defined based on the positional mounting of the compliant plates within the cavity. Known seal assemblies are generally assembled in an attempt to ensure known gap widths are defined between the seal housing and the compliant plates. 
     Generally, variations in sizes of the physical gaps may influence the magnitude of forces exerted on the compliant plates and as such may adversely impact the ability of the plates to prevent axial flow leakage through the seal assemblies. In some known seal assemblies, the size and/or configuration of the front and rear gaps enable lifting forces or blow-down forces to impact the compliant plates. The size and/or configuration of the physical gaps, in some known seal assemblies, are fixed and as a result, such designs limit the control of the forces exerted on the compliant plates. For example, depending on the forces exerted during operation, the compliant plate tips may contact the rotor during shut down of the rotary machine, which may undesirably reduce the life-span of the compliant plates and/or the efficiency of the rotary machine. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one aspect, a method for assembling a rotary machine is provided. The method includes providing at least one seal assembly that includes at least one annular seal housing defined by a top wall, a front wall, and a rear wall, that are connected together such that a cavity is defined within the housing, coupling a plurality of flexible plates within the cavity such that the plates are axially-spaced from the front wall and the rear wall within the cavity, coupling at least one side plate to the at least one annular seal housing such that the at least one side plate is moveable with respect the front wall and the rear wall, and coupling the at least one sealing assembly within a rotary machine to facilitate sealing between a rotary component and a stator component. 
     In another aspect, a seal assembly for a rotary machine is provided. The seal assembly includes an annular seal housing comprising a top wall, a front wall coupled to the top wall, and a rear wall coupled to the top wall such that the rear wall is spaced from the front wall such that a cavity is defined within the housing, a plurality of circumferentially-spaced flexible compliant plates coupled within the cavity, and at least one side plate slidably coupled to at least one of the front wall and the rear wall to facilitate controlling a flow of fluid through at least one of the front wall and the rear wall. 
     In a further aspect, a rotary machine is provided. The rotary machine includes a rotary component including an axis of rotation, a stationary component coupled adjacent to the rotary component, and a seal assembly coupled between the stationary component and the rotary component, the seal assembly comprising an annular seal housing comprising a top wall, a front wall coupled to the top wall, and a rear wall coupled to the top wall, such that a cavity is defined within the housing, a plurality of circumferentially-spaced compliant plates coupled within the cavity, and at least one side plate slidably coupled to at least one of the front wall and the rear wall to facilitate controlling a flow of fluid within the cavity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a portion of an exemplary rotary machine including a seal assembly; 
         FIG. 2  is a cross-sectional view of the seal assembly shown in  FIG. 1  and taken along line  2 - 2 ; 
         FIG. 3  is an axial view of an exemplary side plate used with the seal assembly shown in  FIG. 1 ; 
         FIG. 4  is an axial view of an alternative embodiment of a side plate that may be used with the seal assembly shown in  FIG. 1 ; and 
         FIG. 5  is an axial view of another alternative embodiment of a side plate that may be used with the seal assembly shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     It should be appreciated that the terms “axial” and “axially” are used throughout this application to refer to directions and orientations extending substantially parallel to an axis of rotation of a rotary machine. It should also be appreciated that the terms “radial” and “radially” are used throughout this application to refer to directions and orientations extending substantially perpendicular to the axis of rotation of the rotary machine. It should also be appreciated that the terms “circumferential” and “circumferentially” are used throughout this application to refer to directions that circumscribe the axis of rotation of the rotary machine. 
       FIG. 1  is a perspective view of a portion of an exemplary rotary machine  10  including a seal assembly  100 .  FIG. 2  is a cross-sectional view of seal assembly  100  taken along line  2 - 2 . In the exemplary embodiment, seal assembly  100  includes an annular housing  110  that is substantially U-shaped and that is positioned about a center axis (not shown), and more specifically, about a rotary component or rotor  112 , of rotary machine  10 . Moreover, annular housing  110  is coupled to a fixed stator  114  that is coupled within rotary machine  10  such that annular housing  110  extends between a high pressure side and a low pressure side of rotary machine  10 . In the exemplary embodiment, rotary machine  10  is a steam turbine engine, however, it should be appreciated that rotary machine  10  may be any rotary machine such as, but not limited to, a gas turbine engine. 
     Annular housing  110 , in the exemplary embodiment, includes a top wall  116 , a front wall  118 , and a rear wall  120 . Front and rear walls  118  and  120  each extend generally radially from top wall  116  such that a cavity  122  is defined between front and rear walls  118  and  120 . An inlet gap  124  is defined between front wall  118  and rotor  112 . Inlet gap  124  extends a radial height  125 . An outlet gap  126  is defined between rear wall  120  and rotor  112 . Outlet gap  126  extends a radial height  127 . In the exemplary embodiment, height  125  is approximately equal to height  127 . Alternatively, height  125  may be different than height  127 . 
     A plurality of compliant plates  130  are coupled to an inner surface  132  of top wall  116  such that each plate  130  extends generally radially through cavity  122  towards rotor  112 . Moreover, in the exemplary embodiment, plates  130  are circumferentially-spaced and are oriented such that an annular seal  134  is defined between stator  114  and rotor  112 . Each compliant plate  130  includes a base  136 , a tip  138 , and a body  140  extending therebetween. The base  136  of each compliant plate  130  is coupled to an inner surface  132  of top wall  116 , and each tip  138  is positioned adjacent an outer surface  142  of rotor  112 . In the exemplary embodiment, each compliant plate  130  extends obliquely from inner surface  132  towards rotor  112 , and is oriented such that a clearance gap  144  is defined between each compliant plate tip  138  and rotor outer surface  142 . In the exemplary embodiment, as described in more detail below, each clearance gap  144  varies during rotary machine  10  operation. 
     In the exemplary embodiment, a forward gap  150  is defined between compliant plates  130  and front wall  118 , and an aft gap  152  is defined between compliant plates  130  and rear wall  120 . In the exemplary embodiment, forward gap  150  is generally smaller than aft gap  152 . Alternatively, forward gap  150  may be sized approximately equal to or larger than aft gap  152 . In the exemplary embodiment, front and rear walls  118  and  120  each include two apertures  154  defined therein. In an alternative embodiment, front and rear walls  118  and/or  120  may include more or less than two apertures  154  defined therein. Moreover, in another embodiment, front wall  118  and/or rear wall  120  does not include any apertures  154  defined therein. 
     Annular housing  110 , in the exemplary embodiment, also includes a first side plate  156  that is slidably coupled to an axially forward surface (not shown) of front wall  118 , and a second side plate  158  is slidably coupled to an axially rearward surface (not shown) of rear wall  120 . Alternatively, either first side plate  156  and/or second side plate  158  is rotatably coupled to the respective front and rear walls  118  and  120 . Moreover, in the exemplary embodiment, first and second side plates  156  and  158  each include two apertures  160  defined therein. At least one of the apertures  160  is oriented and sized approximately the same as at least one of the apertures  154  defined in front and/or rear wall  118  and  120 , respectively. 
     In the exemplary embodiment, first and second side plates  156  and  158 , respectively, are each moveable between a first or open position, and a second or sealed position. Specifically, in the open position, either first and/or second side plate  156  and/or  158  facilitates aligning at least one of the side plate apertures  160  with at least one of the apertures  154  defined in the front and/or rear walls  118  and  120 , such that a passageway  164  is defined by apertures  154  and  160 . Passageway  164  extends through first side plate  156  and front wall  118 , and more specifically, from the high pressure side of rotary machine  10  to forward gap  150 . Passageway  164  enables fluid to flow from the high pressure side of rotary machine  10  into cavity  122 . Alternatively, passageway  164  may extend through second side plate  158  and rear wall  120 . In the sealed position, either first or second side plate  156  and  158  facilitates sealing at least one of the apertures  154  defined in the either front and/or rear wall  118  and  120 , to facilitate preventing fluid from being channeled through the aperture  154 . In the exemplary embodiment, and illustrated in  FIG. 2 , first side plate  156  is positioned in the open position, and second side plate  158  is positioned in the sealed position. 
       FIG. 3  is an axial view of side plate  156 . It should be understood that in the exemplary embodiment, side plate  156  is substantially identical to side plate  158 . As such, the following description also applies to side plate  158 . In the exemplary embodiment, side plate  156  is substantially circular and is aligned substantially concentrically with respect to a center axis  166  that is substantially coaxial with respect to the axis of rotation of rotor  112  (shown in  FIG. 2 ). Side plate  156 , in the exemplary embodiment, also includes a plurality of sections  168  that are slidable radially outward from center axis  166 . Each section  168  includes two apertures  160  defined therein that are sized and oriented approximately the same as apertures  154  (shown in  FIG. 2 ). Alternatively, first side plate  156  may include any number of apertures  160  that enables seal assembly  100  (shown in  FIG. 1 ) to function as described herein. 
     In the exemplary embodiment, during operation, an actuating means (not shown) moves each section  168  radially outward from center axis  166 . More specifically, during operation, each section  168  is moved to either the open position or the closed position. The actuating means may be any means that enables side plate  156  to function as described herein, such as, but not limited to, biasing members and/or bellows. 
     During operation the flow of fluid is generally channeled from the high pressure area to the low pressure area. In a first configuration, first and second side plates  156  and  158  are each positioned in the sealed position. In such an orientation the flow of fluid is channeled through inlet gap  124  and into cavity  122 . The flow of fluid is then channeled generally radially through forward gap  150  and generally axially through clearance gap  144 . Moreover, at least a portion of fluid is channeled past compliant plates  130 . Fluid contained within cavity  122  is discharged from seal assembly  100  through outlet gap  126 . Such an orientation of plates  156  and  158  causes lifting forces to be exerted on compliant plates  130  such that tips  138  are forced away from rotor  112 . Moreover, in such a configuration, the flow of fluid through seal assembly  100  is facilitated to be minimized because apertures  154  defined in front and rear walls  118  and  120  are substantially sealed by first and second side plates  156  and  158 , respectively. 
     In a second configuration, first side plate  156  is positioned in the open position and second side plate  158  is positioned in the sealed position. In such an orientation, fluid is channeled through inlet gap  124  and passageway  164 , through apertures  160  and  154  defined in plate  156  and front wall  118 , respectively, into cavity  122 . The flow of fluid is further channeled generally radially through forward gap  150  and generally axially through clearance gap  144 . Moreover, at least a portion of the fluid flow is channeled past compliant plates  130 . Fluid contained within cavity  122  is discharged from seal assembly  100  through outlet gap  126 . Such a configuration causes blow down forces to be exerted on compliant plates  130  such that tips  138  are forced closer to rotor  112 . Moreover, in the second configuration, the flow of fluid through seal assembly  100  is facilitated to be increased in comparison to the first configuration because first side plate  156  is positioned in the open position, such that additional fluid is channeled into cavity  122 . 
     In a third configuration, first and second side plates  156  and  158  are each positioned in the open position. In such an orientation, fluid is channeled through inlet gap  124  and passageway  164 , through apertures  160  and  154  and front wall  118 , respectively, into cavity  122 . The flow of fluid is also channeled generally radially through forward gap  150  and generally axially through clearance gap  144 . Moreover, at least a portion of fluid is channeled past compliant plates  130 . Fluid contained within cavity  122  is discharged from seal assembly  100  through outlet gap  126  and passageway  164 , through apertures  160  and  154 . Such an orientation causes lifting forces to be exerted on compliant plates  130  such that tips  138  are forced away from rotor  112 . Moreover, in such a configuration, the flow of fluid through seal assembly  100  is facilitated to be increased in comparison to the previously described configurations because first and second side plates  156  and  158  are positioned in the open position, such that additional fluid is channeled through seal assembly  100  than is channeled through seal assembly  100  in the first and second configurations. 
     In a fourth configuration, first side plate  156  is positioned in the sealed position and second side plate  158  is positioned in the open position. In such an orientation, the flow of fluid is channeled through inlet gap  124  into cavity  122 . The flow of fluid is further channeled generally radially through forward gap  150  and generally axially through clearance gap  144 . Moreover, at least a portion of fluid flow is channeled past compliant plates  130 . Fluid contained within cavity  122  is discharged from seal assembly  100  through outlet gap  126  and passageway  164  through apertures  160  and  154 . Such a configuration causes lifting forces to be exerted on compliant plates  130 , wherein such lifting forces are greater than the lifting forces generated in the first configuration. Moreover, in the fourth configuration, the flow of fluid through seal assembly  100  is substantially equivalent to the flow of fluid through seal assembly  100  in the first configuration because front wall apertures  154  are sealed. 
     In the exemplary embodiment, the first, third, and fourth configurations each cause exerting lifting forces to be exerted on compliant plates  130  such that tips  138  are lifted away from rotor  112 . Such configurations enable non-contact operation of rotary machine  10  during low pressure gradient conditions, such as, but not limited to, shut down operations and start-up operations. The second configuration causes blow-down forces to be exerted on compliant plates  130  such that tips  138  are forced closer to rotor  112 . The second configuration enables clearance gap  144  to be minimized during high pressure gradient conditions, such as during electric power generation conditions, such that the flow of fluid through seal assembly  100  is facilitated to be reduced. 
       FIG. 4  is an axial view of an alternative side plate  256  that may be used with assembly  100  (shown in  FIG. 1 ). In the exemplary embodiment, side plate  256  is substantially circular and is aligned substantially concentrically with respect to a center axis  266  that is substantially coaxial with respect to the axis of rotation of rotor  112  (shown in  FIG. 2 ). Side plate  256 , in the exemplary embodiment, includes four apertures  260  defined therein. Alternatively, side plate  256  may include any number of apertures  260  that enables seal assembly  100  to function as described herein. Each aperture  260  is sized and oriented approximately the same as to each aperture  154 . 
     In the exemplary embodiment, during operation, a rotating means (not shown) rotates side plate  256  circumferentially about center axis  266  to open position or the sealed position. In the exemplary embodiment, the rotating means may be any means that enables first side plate  256  to function as described herein. 
       FIG. 5  is an axial view of another alternative side plate  356  that may be used with assembly  100  (shown in  FIG. 1 ). In the exemplary embodiment, side plate  356  is substantially circular and circumscribes a center axis  366  that is coaxial with and is aligned substantially concentrically with respect to the axis of rotation of rotor  112  (shown in  FIG. 1 ). Side plate  356 , in the exemplary embodiment, includes an aperture  160  defined therein that extends generally helically about center axis  366 . Alternatively, side plate  356  may include any number of apertures  360  that enables seal assembly  100  to function as described herein. Each aperture  360  is sized and oriented approximately the same as apertures  154  (shown in  FIG. 2 ). 
     During operation, in the exemplary embodiment, a rotating means (not shown) rotates first side plate  356  circumferentially about center axis  366  to either the open position or the sealed position. In the exemplary embodiment, the rotating means may be any means that enables first side plate  356  to function as described herein. 
     In the exemplary embodiment, side plates  156  and  158  facilitate controlling the forces exerted on compliant plates  130  and the amount of flow channeled past compliant plates  130 . More specifically, first and second plates  156  and  158  facilitate controlling an amount of flow channeled through either front and/or rear wall  118  and  120 . 
     The above-described methods and apparatus facilitate sealing between a high pressure area and a low pressure area defined within a rotary machine by controlling the forces exerted on a plurality of compliant plates coupled within a seal assembly. Specifically, each seal assembly includes a side plate that is slidably coupled to either the front wall and/or the rear wall of an annular seal housing. Each side plate includes at least one aperture defined therein that is oriented and sized approximately the same as an aperture defined in either the front and/or rear wall. Moreover, each side plate is moveable, with respect to the respective front and rear walls, between an open position and a sealed position. The open position enables the apertures defined in the front and/or rear walls to be opened, and the sealed position enables the apertures defined in the front and/or rear walls to be sealed. As a result, a plurality of different configurations are possible which enable the amount of the fluid flow channeled through the seal assembly  100  to be controlled. Moreover, such control facilitates preventing compliant plate tip contact with the rotor during pre-determined operating conditions of low pressure gradients. As a result, rotor performance and useful life of such seal assemblies are facilitated to be improved. 
     Exemplary embodiments of seal assemblies are described in detail above. The seal assembly described herein is not limited to use with the rotary machines described herein, but rather, the seal assembly can be utilized independently and separately the rotary machine and/or rotor components described herein. Moreover, the invention is not limited to the embodiments of the seal assemblies described above in detail. Rather, other variations of the seal assembly mixers may be utilized within the spirit and scope of the claims. 
     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.