Patent Publication Number: US-2023133059-A1

Title: Compressor rotor having seal elements

Description:
BACKGROUND 
     Disclosed embodiments relate generally to the field of turbomachinery, and, more particularly, to a rotor structure for a turbomachine, such as a compressor. 
     Turbomachinery is used extensively in the oil and gas industry, such as for performing compression of a process fluid, conversion of thermal energy into mechanical energy, fluid liquefaction, etc. One example of such turbomachinery is a compressor, such as a centrifugal compressor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates a fragmentary cross-sectional view of one non-limiting embodiment of a disclosed rotor structure, as may be used in industrial applications involving turbomachinery, such as without limitation, centrifugal compressors. 
         FIG.  2    illustrates a zoomed-in, cross-sectional view of one non-limiting embodiment of a disclosed seal element for a compressor rotor and two adjacent rotor components onto which the seal element is affixed. The seal element being movable between a first position (e.g., a pre-assembly position) and a second position (e.g., assembled position).  FIG.  2    illustrates the disclosed seal element when in the pre-assembly position. 
         FIG.  3    illustrates the disclosed seal element shown in  FIG.  2    when in the assembled position. 
         FIG.  4    is a superposition of  FIGS.  2  and  3    illustrating a dashed outline of the seal element when in the assembled position ( FIG.  3   ). The dashed outline of the seal element is superimposed on the seal element when in the pre-assembly position shown in  FIG.  2   . 
         FIG.  5    illustrates a zoomed-in, cross-sectional view of another non-limiting embodiment of a disclosed seal element and two adjacent rotor components onto which the seal element is affixed. The seal element being movable between the pre-assembly position and the assembled position.  FIG.  5    illustrates the disclosed seal element when in the pre-assembly position. 
         FIG.  6    illustrates the disclosed seal element shown in  FIG.  5    when in the assembled position. 
         FIG.  7    is a superposition of  FIGS.  5  and  6    illustrating a dashed outline of the seal element when in the assembled position ( FIG.  6   ). The dashed outline of the seal element is superimposed on the seal element when in the pre-assembly position shown in  FIG.  5   . 
     
    
    
     DETAILED DESCRIPTION 
     As would be appreciated by those skilled in the art, turbomachinery, such as centrifugal compressors, may involve rotors of tie bolt construction (also referred to in the art as thru bolt or tie rod construction), where the tie bolt supports a plurality of impeller bodies and where adjacent impeller bodies may be interconnected to one another by way of elastically averaged coupling techniques, such as involving hirth couplings or curvic couplings. These coupling types use different forms of face gear teeth (straight and curved, respectively) to form a robust coupling between two components. 
     These couplings and associated structures may be subject to greatly varying forces (e.g., centrifugal forces), such as from an initial rotor speed of zero revolutions per minute (RPM) to a maximum rotor speed, (e.g., as may involve tens of thousands of RPM). Additionally, these couplings and associated structures may be exposed to contaminants and/or byproducts that may be present in process fluids processed by the compressor. If so exposed, such couplings and associated structures could be potentially affected in ways that could impact their long-term durability. By way of example, a combination of carbon dioxide (CO2), liquid water and high-pressure levels can lead to the formation of carbonic acid (H2CO3), which is a chemical compound that can corrode, rust or pit certain steel components. Physical debris may also be present in the process fluids that if allowed to reach the hirth couplings and associated structures could potentially affect their functionality and durability. 
     In view of the foregoing considerations, the present inventor has recognized that attaining consistent high performance and long-term durability in a centrifugal compressor, for example, may involve in disclosed embodiments appropriately covering respective hirth couplings with appropriate sealing structures to inhibit passage onto the respective hirth coupling of process fluid being processed by the compressor, and thus ameliorating the issues discussed above. 
     In the following detailed description, various specific details are set forth in order to provide a thorough understanding of such embodiments. However, those skilled in the art will understand that disclosed embodiments may be practiced without these specific details that the aspects of the present invention are not limited to the disclosed embodiments, and that aspects of the present invention may be practiced in a variety of alternative embodiments. In other instances, methods, procedures, and components, which would be well-understood by one skilled in the art have not been described in detail to avoid unnecessary and burdensome explanation. 
     Furthermore, various operations may be described as multiple discrete steps performed in a manner that is helpful for understanding embodiments of the present invention. However, the order of description should not be construed as to imply that these operations need be performed in the order they are presented, nor that they are even order dependent, unless otherwise indicated. Moreover, repeated usage of the phrase “in one embodiment” does not necessarily refer to the same embodiment, although it may. It is noted that disclosed embodiments need not be construed as mutually exclusive embodiments, since aspects of such disclosed embodiments may be appropriately combined by one skilled in the art depending on the needs of a given application. 
       FIG.  1    illustrates a fragmentary, cross-sectional view of one non-limiting embodiment of a disclosed rotor compressor  100 , as may be used in industrial applications involving turbomachinery, such as without limitation, compressors (e.g., centrifugal compressors, etc.). 
     In one disclosed embodiment, a tie bolt  102  extends along a rotor axis  103  between a first end and a second end of the tie bolt  102 . To avoid visual cluttering, just one end of the tie bolt is illustrated since, for purposes of the present disclosure, the structural and/operational relationships in connection with each end of the tie bolt  102  are the same. A rotor shaft  104  may be fixed to the first end of tie bolt  102 . A second rotor shaft may be fixed to the second end of the tie bolt (as noted above, neither the second end of the tie bolt nor the second rotor shaft are shown). The rotor shafts may be referred to in the art as stubs shafts. It will be appreciated that in certain embodiments more than two rotor shafts may be involved. 
     A plurality of impeller bodies may be disposed between the rotor shafts and supported by tie bolt  102 . For simplicity of illustration, a first impeller body  106   1  and a just a portion of a second impeller body  106   2  are illustrated in  FIG.  1   . By way of example, a back side of impeller body  106   1  is mechanically coupled to an inlet side of impeller body  106   2  for rotation about the rotor axis  103  by way of a hirth coupling  108 . In the illustrated embodiment, an additional hirth coupling  109  may be used to respectively mechanically couple the inlet side of impeller body  1061 with adjacent rotor shaft  104 . It will be appreciated that the foregoing arrangement of impeller bodies and hirth couplings is just one example and should not be construed in a limiting sense. 
     A seal element  120  is affixed onto respective outward surfaces of any two adjacent impeller bodies (e.g., adjacent impeller bodies  106   1 ,  106   2 ). Seal element  120  may be arranged to span (e.g., along 360 degrees) a circumferentially extending spacing  126  between adjacent impeller bodies  106   1 ,  106   2  to inhibit passage onto respective hirth coupling  108  of process fluid being processed by the compressor. Similarly, a seal element  130  is affixed onto respective outward surfaces of an impeller body and an adjacent rotor shaft (e.g., impeller body  106   1  and adjacent rotor shaft  104 ) to inhibit passage onto hirth coupling  109  of the process fluid being processed by the compressor. 
     As elaborated in greater detail below, seal element  120  may be respectively movable between a first position (the pre-assembly position) and a second position (the assembled position). The foregoing movable features of seal element  120  are equally applicable to seal element  130 .  FIG.  2    illustrates seal element  120  when in the first position and  FIG.  3    illustrates seal element  120  when in the second position. 
       FIG.  4    is a superposition of  FIGS.  2  and  3    illustrating an outline (schematically represented by dashed lines) of the seal element when in the assembled position ( FIG.  3   ), which is superimposed on the seal element when in the pre-assembly position shown in  FIG.  2   . 
     As may be better appreciated in  FIGS.  2  and  3   , seal element  120 , for example, may have a first end  121  mechanically coupled to a second rotor component  106 ″ and a second end  123  mechanically coupled to a first impeller body  106 ′. In general, second rotor component  106 ″ may be any given rotor component, such as a second impeller body, a rotor shaft or a balance piston, adjacent to first impeller body  106 ′ and mechanically connected to first impeller body  106 ′ for rotation about the rotor axis by way of a hirth coupling, as discussed above in the context of FIG. 1 . Accordingly, the description below may be similarly applicable regardless of whether the second rotor component  106 ″ is an impeller body, a rotor shaft or a balance piston. For simplicity of illustration, the hirth couplings that connect first impeller body  106 ′ to second rotor component  106 ″ are not illustrated in  FIG.  2 - 7   . 
     Without limitation, first impeller body  106 ′ may define a frustoconical outer surface  140  having a first angle, which is fixed with respect to the rotor axis. The second end  123  of seal element  120  may define a frustoconical inner surface  142  having a second angle that is elastically changeable with respect to the rotor axis, and thus changeable with respect to frustoconical outer surface  140 . 
     As can be appreciated in  FIG.  2   , in the first position (e.g., the pre-assembly position) the first angle of frustoconical outer surface  140  and the second angle of frustoconical inner surface  142  are such to permit frustoconical surfaces  140 ,  142  to contact one another at a point  144 , such as may define an initial contact point of the second end  123  of seal element  120  with frustoconical outer surface  140 , for example. As can be appreciated in  FIG.  3   , in the second position (e.g., the assembled position) the first angle of frustoconical outer surface  140  and the second angle of frustoconical inner surface  142  are such to permit frustoconical surfaces  140 ,  142  to make surface-to-surface engagement, as schematically represented by twin-headed arrow  146 . 
     That is, the frustoconical inner surface  142  of seal element  120 , such as in response to axial compressive loading applied by second rotor component  106 ″ with respect to first impeller body  106 ′, causes the frustoconical inner surface  142  of seal element  120  to elastically flex, as seal element  120  moves together with second rotor component  106 ″ in a direction opposite the first axial end  121  of seal element  120  toward first impeller body  106 ′ and engages onto the frustoconical outer surface  140  of first impeller body  106 ′. The flexing of frustoconical inner surface  142  of seal element  120  causes the seal element to be in a spring-loaded condition, which in turn generates a biasing force arranged to circumferentially clamp onto the frustoconical outer surface  140  of first impeller body  106 ′. It will be appreciated that for servicing operations, for example, seal element  120  may be movable from the second position (the assembled position) to the first position, which in this case would permit user-friendly removal and/or replacement of seal element  120 . 
     As shown in  FIGS.  2 - 3   , second rotor component  106 ″ may include a cylindrical outer surface  141 , where the first end  121  of seal element  120  may be affixed to the cylindrical outer surface  141  by way of a slip fit or by way of an interference fit, (which may also be referred in the art as a press fit), and which, for example, could involve shrink-fitting techniques for affixing the first end  121  of seal element  120  onto the cylindrical outer surface  141  of second rotor component  106 ″. 
     In one non-limiting embodiment, a first circumferentially-extending groove  160  may be disposed in the frustoconical outer surface  140  of first impeller body  106 ′ and a first seal member  162  may be positioned in the groove  160  to form a seal between the frustoconical outer surface  140  of of first impeller body  106 ′ and the seal element  120 . 
     In one non-limiting embodiment, a second circumferentially-extending groove  170  may be disposed in the cylindrical outer surface  141  of second rotor component  106 ″, and a second seal member  172  may be positioned in the groove  170  to form a seal between the cylindrical outer surface  141  of second rotor component  106 ″ and the seal element  120 . 
     Without limitation, seal member  162  or seal member  172  may be an  0 -ring seal member, which may comprise an elastomeric material or a non-elastomeric material, such as PTFE (Polytetrafluoroethylene) material, a C-shaped seal member, a leaf seal member, an omega-shaped seal member, a metallic seal member, a metallic cloth seal member or other seal member. As will be appreciated by one skilled in the art, a metallic cloth seal may comprise a high temperature-resistant material, such as metal, ceramic or polymer fibers which may be woven, knitted or otherwise pressed into a layer of fabric. 
     As may be appreciated in  FIG.  4   , angle θ schematically represents an angle that frustoconical inner surface  142 ″ of seal element  120  would flex when in the second position (e.g., the assembled position) to circumferentially clamp onto the frustoconical outer surface  140  of first impeller body  106 ′. Frustoconical inner surface  142 ′ is indicative of seal element  120  when in the first position, where frustoconical inner surface  142 ′ is at an angle that permits frustoconical surfaces  140 ,  142 ′ to contact one another at point  144 . 
     In one non-limiting embodiment, as shown in  FIGS.  2 - 3   , first impeller body  106 ′ may define a first outer surface  148  having a first contour, second rotor component  106 ″ may define a second outer surface  150  having a second contour and seal element  120  may define an outer surface  122  that provides a continuous contour transition between the first contour and the second contour. 
     In the embodiment illustrated in  FIGS.  2 - 3   , the outer surface  122  of seal element  120  may comprise a curving contour transition between the first contour defined by the first outer surface  148  of first impeller body  106 ′ and the second contour defined by the second outer surface  150  of second rotor component  106 ″. That is, the contour transition defined by the outer surface  122  of seal element  120  may be comprise a singular type of contour geometry, such as a curving contour geometry. 
     By way of comparison, in the embodiment illustrated in  FIGS.  5 - 6   , the outer surface  122 ′ of seal element  120 ′ may comprise a cylindrical contour that extends from the first end  121  of seal element  120 ′ to a point  125  (between first end  121  and second end  123  of seal element  120 ′) where the outer surface  122 ′ of seal element  120 ′ changes to a non-cylindrical contour, e.g., a curving contour. That is, the contour transition defined by the outer surface  122 ′ of seal element  120 ′ may comprise two different types of contour geometries, such as a cylindrical contour and a curving contour. 
     Further structural and/or operational features described above in the context of  FIGS.  2 - 4    in connection with seal element  120  are equally applicable to seal element  120 ′. For example, seal element  120 ′ may be respectively movable between a first position (the pre-assembly position) and a second position (the assembled position).  FIG.  5    illustrates seal element  120 ′ when in the first position and  FIG.  6    illustrates seal element  120 ′ when in the second position.  FIG.  7    is a superposition of  FIGS.  5  and  6    illustrating an outline (schematically represented by dashed lines) of seal element  120 ′ when in the assembled position ( FIG.  6   ), which is superimposed on seal element  120 ′ when in the pre-assembly position shown in  FIG.  5   . Accordingly, such structural and/or operational features, having already been described with enough detail in the context of  FIGS.  2 - 4   , will not be reiterated here to spare the reader from burdensome and pedantic repetition. 
     In operation, disclosed embodiments make use of seal elements appropriately arranged to cover the hirth couplings and effective to inhibit passage onto the respective hirth coupling of process fluid being processed by the compressor, and thus inhibiting potential exposure of the hirth couplings and associated structures to contaminants, chemical byproducts, and/or physical debris. 
     In operation, disclosed embodiments permit user-friendly assembly of the seal elements onto respective outward surfaces of any two adjacent rotor components, such as adjacent impeller bodies or a rotor shaft and an adjacent impeller body. Additionally, disclosed embodiments permit user-friendly disassembly of the seal elements from the respective outward surfaces of any two such adjacent rotor components that, for example, facilitate servicing operations. 
     While embodiments of the present disclosure have been disclosed in exemplary forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the scope of the invention and its equivalents, as set forth in the following claims.