Abstract:
A seal for a turbine system includes a rotor, a bowl region and a stator assembly having a tip strip disposed proximate the rotor. Also included is a packing head disposed proximate the tip strip. Further included is a flex seal having a first end portion fixedly secured to at least one of the tip strip and the packing head, with a second end portion slidably engaged with at least one of the tip strip and the packing head.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to turbine systems, and more particularly to a seal for such turbine systems. 
         [0002]    Turbine systems, such as steam turbine systems, for example, often include different sections that operate at various pressures, including a high pressure (HP) section and an intermediate pressure (IP) section, each housing a portion of a rotor. During operation, it is common for a cooling source to be introduced to the area of the IP section proximate the rotor, in order to maintain the temperature of the rotor below the temperature of the general IP section. Failure to achieve maintenance of the rotor surface at a cooler temperature results in a need to reduce the rotor diameter design, but the reduced diameter negatively impacts overall steam turbine system performance. 
         [0003]    Steam from the HP section often leaks across packing, such as N2 packing, toward the lower pressure environment of the IP section, and may provide the cooling source for the rotor. Preventing a separate steam source, namely the relatively hot IP section steam, from reaching the rotor surface requires sealing between stators proximate the rotor surface. Previous efforts to seal such locations from the hot IP section steam have encountered issues with radial and axial displacement of the stators during operation of the steam turbine system, with which the seals are often in contact. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    According to one aspect of the invention, a seal for a turbine system includes a rotor, a bowl region and a stator assembly having a tip strip disposed proximate the rotor. Also included is a packing head disposed proximate the tip strip. Further included is a flex seal having a first end portion fixedly secured to at least one of the tip strip and the packing head, with a second end portion slidably engaged with at least one of the tip strip and the packing head. 
         [0005]    According to another aspect of the invention, a seal for a steam turbine system includes a rotor, a bowl region and a stator assembly including a stator tip strip, wherein the stator tip strip is disposed proximate the rotor. Also included is a first steam source injected into the bowl region at a first temperature. Further included is a packing head disposed proximate the stator tip strip. Yet further included is a rotor cooling steam source injected at a second temperature along a path in close proximity to the rotor, wherein the second temperature is lower than the first temperature. Also included is a flex seal having a fixed portion and a free portion, wherein the flex seal is fixedly coupled at the fixed portion to at least one of the stator assembly, the packing head and the stator tip strip, wherein the flex seal prevents the first steam source from entering the path in close proximity to the rotor. 
         [0006]    According to yet another aspect of the invention, a seal for a steam turbine system includes an intermediate pressure section having a rotor, a bowl region, an outer casing and a stator assembly having a tip strip disposed proximate the rotor, wherein the intermediate pressure section comprises an axial direction corresponding to a longitudinal direction of the rotor and a radial direction extending relatively from the rotor to the outer casing. Also included is a packing head disposed proximate the tip strip. Further included is a flex seal having a first end portion fixedly secured to at least one of the tip strip and the packing head, with a second end portion slidably engaged with at least one of the tip strip and the packing head and configured to be displaced in the axial direction and the radial direction. 
         [0007]    These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0008]    The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0009]      FIG. 1  is a schematic illustration of a steam turbine system; 
           [0010]      FIG. 2  is a cross-sectional view of an inlet region of an intermediate pressure section of the steam turbine system illustrating a flex seal according to one embodiment; 
           [0011]      FIG. 3  is a cross-sectional view of the flex seal illustrated in  FIG. 2 ; 
           [0012]      FIG. 4  is a cross-sectional view of the flex seal according to a second embodiment; 
           [0013]      FIG. 5  is a cross-sectional view of the flex seal according to a third embodiment; and 
           [0014]      FIG. 6  is a cross-sectional view of the flex seal according to a fourth embodiment. 
       
    
    
       [0015]    The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    Referring to  FIG. 1 , a turbine system and more specifically an opposed-flow steam turbine system is generally illustrated with the reference numeral  10 . The steam turbine system  10  includes a high pressure (HP) section  12  and an intermediate pressure (IP) section  14 , with the HP section  12  being defined by an HP casing  16 , and similarly the IP section  14  being defined by an IP casing  18 . A central section  20  disposed between the HP section  12  and the IP section  14  includes a high pressure steam inlet  22  and an intermediate pressure steam inlet  24 . 
         [0017]    An annular section divider  26  extends radially inwardly from the central section  20  towards a rotor  28  that extends between the HP section  12  and the IP section  14 . More specifically, the annular section divider  26  extends circumferentially around a portion of the rotor  28  between an HP section inlet nozzle  30  and an IP section inlet nozzle  32 . The annular section divider  26  has a packing structure  50  annularly fitted close to the rotor  28 . 
         [0018]    In operation, the high pressure steam inlet  22  receives high pressure, high temperature steam from a steam source, such as a boiler (not illustrated), for example. Steam is routed through the HP section  12  from the first HP section inlet nozzle  30 , from which work is extracted from the steam to mechanically rotate the rotor  28  via a plurality of turbine blades  27 , or buckets (shown in  FIG. 2 ) which are operably coupled to the rotor  28 . Each set of buckets includes a corresponding stator  29  (shown in  FIG. 2 ) that facilitates routing of steam to the associated buckets. The steam exits the HP section  12  and is returned to the boiler, where the steam is then reheated. The reheated steam is then routed to the intermediate pressure steam inlet  24  and returned to the IP section  14  via the IP section inlet nozzle  32  at a reduced pressure than steam entering the HP section  12 , but at a temperature that is approximately equal to the temperature of the steam entering the HP section  12 . Work is extracted from the steam in the IP section  14  in a similar manner as that employed for the HP section  12  via a system of rotating and stationary components. Accordingly, an operating pressure within the HP section  12  is higher than an operating pressure within the IP section  14 , such that steam within the HP section  12  tends to flow towards the IP section  14  through leakage paths that may develop between the HP section  12  and the IP section  14 . 
         [0019]    Although the steam turbine system  10  has been described as an opposed-flow high pressure and intermediate pressure steam turbine combination, it is to be appreciated that the steam turbine system  10  may be employed with any individual turbine including, but not limited to, low pressure turbines. Additionally, the steam turbine system  10  is not limited to being configured as an opposed-flow steam turbine, but may instead be configured as a single-flow or double-flow steam turbine system, for example. Moreover, it is contemplated that embodiments disclosed herein may be used in conjunction with gas turbine systems as well. 
         [0020]    Referring to  FIG. 2 , a cross-sectional portion of the IP section  14  is shown in greater detail. The IP section  14  includes an IP bowl  40  proximate the IP section inlet nozzle  32 , wherein a stream  42  of high temperature, intermediate pressure steam is injected into the IP bowl  40  for routing through the IP section  14 , as described above. The stator  29  within the IP section  14  is operably connected at a radially outward position to the IP casing  18  and includes a tip strip  46  that is disposed proximate the rotor  28 . Adjacent to, and in close proximity with, the tip strip  46  of the stator  29  is a packing head  48  of the packing structure  50  disposed between the HP section  12  and the IP section  14 . In order to maintain the rotor  28  at a suitable application temperature, a cooling source may be introduced proximate the rotor  28 . Such a cooling source may comprise a leaked flow  52  from the HP section  12  that has leaked across the N2 packing structure  50 . The leaked flow  52  that comprises high pressure steam from the HP section  12  naturally tends to flow in the direction of the lower pressure IP section  14 . As the leaked flow  52  travels from the HP section  12  to the IP section  14 , the temperature of the leaked flow  52  decreases, thereby providing a cooler flow to the rotor  28  than would otherwise be felt by the rotor  28  as a result of heat transfer stemming from the stream  42  generally flowing through the IP section  14 . It is to be appreciated that the cooling source has been described as the leaked flow  52  from the HP section  12  across the N2 packing structure  50 , however, various alternative cooling sources may be employed to maintain the temperature of the rotor  28  below that of the general IP section  14 . 
         [0021]    As illustrated, a gap  54  between the packing head  48  and the tip strip  46  of the stator  29  is present. Unsealed, the gap  54  may result in a direct path of the stream  42 , which may have a varying temperature of about 1,100° F., toward the rotor  28 . Additionally, mixing of the stream  42  with a cooling source, such as the leaked flow  52 , hinders the efficiency of the rotor cooling effort. In order to prevent passage of the stream  42  through the gap  54 , a flex seal  60  is disposed within the gap  54 . The flex seal  60  includes a first end portion  62  and a second end portion  64 , with one of the first end portion  62  or the second end portion  64  being operably coupled to the tip strip  46 , or more generally the stator  29 , or the packing head  48 . The end not operably coupled to an object, that being either the first end portion  62  or the second end portion  64  is fittingly engaged with either the tip strip  46  or the packing head  48  and relatively free to displace. In other words, irrespective of whether the first end portion  62  or the second end portion  64  is operably coupled to the tip strip  46  or the packing head  48 , the other end is fittingly engaged with the other object, specifically the tip strip  46  or the packing head  48 . 
         [0022]    The ability of the first end portion  62  or the second end portion  64  to displace is based on the tendency of stator components, such as the tip strip  46  and the packing head  48  to displace in an axial and/or a radial direction during operation of the steam turbine system  10 . Therefore, tight seals having a pressure fit at both the first end portion  62  and the second end portion  64  or an operable connection at the first end portion  62  and the second end portion  64  are not adequately held within the gap  54 . The allowance of the flex seal  60  to displace proximate at least one end in correspondence with an associated structure, such as the tip strip  46  or the packing head  48 , maintains a robust seal of the gap  54 , while accommodating the axial and/or radial displacement of the tip strip  46  or the packing head  48 . 
         [0023]    Referring to  FIGS. 3-6 , enlarged views of various embodiments of the flex seal  60  are illustrated. It is to be appreciated that the geometries of the flex seal  60  shown are merely illustrative, and are not limiting, as numerous geometric variations of the flex seal  60  are contemplated. Irrespective of the specific geometry employed for the flex seal  60 , included is the first end portion  62  and the second end portion  64 , with each being disposed in contact with the tip strip  46  and the packing head  48 , respectively. As previously described, only one end of the flex seal  60  is operably coupled to one of the tip strip  46  and the packing head  48 . By way of example, the first end portion  62  may be operably coupled to the tip strip  46  via mechanical fastening, such as bolting, riveting, or welding. These manners of mechanically fastening the first end portion  62  to the tip strip  46  are merely examples, and any suitable fastener may be employed to ensure retention of the first end portion  62  to the tip strip  46 . Continuing with the example, the second end portion  64  is in fitting engagement with the packing head  48 , yet not operably coupled in a fixed manner, such that displacement may be achieved during axial and/or radial displacement of the tip strip  46  and/or the packing head  48 . Adequate sealing and engagement of the second end portion  64  with the packing head  48  is achieved by pre-pressurizing the flex seal  60  to maintain sealing during even relatively large displacements. 
         [0024]    The various embodiments of the flex seal  60  are illustrated and may be characterized as “Y-shaped” ( FIG. 3 ), “S-shaped” ( FIG. 4 ), or variations thereof ( FIGS. 5 and 6 ). While described as having the first end portion  62  and the second end portion  64  that are either operably coupled or in fitting engagement with the associated structural components, it is to be appreciated that the end is not necessarily the portion that requires such a connection. As seen in  FIG. 6 , for example, the second end portion  64  is not disposed in contact with the packing head  48 , and as such it may be another portion of the flex seal  60  that provides the operable connection or the fitting engagement. As described above, the illustrated embodiments of the flex seal  60  are merely examples of the numerous contemplated configurations that may be employed to prevent the high temperature steam, in the form of the stream  42 , from intruding the rotor area through the gap  54 . 
         [0025]    Advantageously, the flex seal  60  prevents the high temperature steam routing through the IP section  14  from being imposed on the surface of the rotor  28 , while maintaining adequate structural integrity at seal contact points. 
         [0026]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.