Patent Publication Number: US-2021164489-A1

Title: Compressor having extended range and stability

Description:
BACKGROUND 
     Embodiments of the disclosure relate generally to a refrigeration system, and more particularly, to a ported shroud for extending the range of a centrifugal compressor. 
     Rotary machines are commonly used in refrigeration and turbine applications. An example of a rotary machine includes a centrifugal compressor having an impeller fixed to a rotating shaft. Rotation of the impeller increases a pressure and/or velocity of a fluid or gas moving across the impeller. The impeller is typically surrounded by a generally conical or bell-shaped shroud, which helps guide the flow from the forward section to the aft section of the impeller. Certain benefits in impeller performance can be realized by forming one or more ports through the impeller shroud to allow fluid flow in one of two directions depending upon the operational conditions of the impeller. The flow extracted from the impeller under outflow conditions may be discharged from the compressor, provided to another component of the system, or possibly redirected back to the inlet of the impeller by a recirculation flow pathway for reingestion by the impeller. 
     Conventionally, constraints on the arrangement of components require the bleed outlet to remain in close proximity upstream of the impeller inducer. Such positioning of the bleed outlet impacts the profile of the impeller inlet flow, which must be accounted for in the design of the compressor. For a wide flow capability compression system, such as those used in chiller applications for example, it may be difficult to maintain desired performance over the full flow range of the compressor. 
     BRIEF DESCRIPTION 
     According to an embodiment, a ported shroud for use in a compressor includes a body having a first end and a second opposite end. The body is disposed concentrically about an axial passageway and includes an inlet for receiving a fluid flow formed adjacent the first end and an outlet port for discharging the fluid flow formed adjacent the second end. A toroidal volute is disposed within the interior of the body and fluidly couples the inlet and the outlet. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments at least one of a size and contour of the inlet is selected based on a pressure distribution within the compressor. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the inlet includes a slot. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the slot extends circumferentially about the axial passageway. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the slot includes a ramped surface extending from the first end toward the second end. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the ramped surface gradually increases in distance from the first end about a circumferential of the axial passageway, the distance being measured parallel to an axis of the axial passageway. 
     According to another embodiment, a compressor includes a housing including an inlet opening formed at a first end of the housing and an internal wall extending from the inlet opening to define a passageway. An impeller including at least one impeller blade is rotatable about an axis and is positioned adjacent an end of the passageway for receiving a fluid flow there through. A ported shroud is positioned adjacent at least a portion of the internal wall. The ported shroud includes an internal volute and includes a first opening in fluid communication with a leading edge of the at least one impeller blade. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the ported shroud includes a second opening in fluid communication with a component external to the compressor. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments during outflow operation, fluid is provided to the ported shroud through the first opening and is discharged from the ported shroud through the second opening. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments during inflow operation, fluid is provided to the ported shroud through the second opening and is discharged from the ported shroud through the first opening. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the ported shroud is integrally formed with the internal wall of the housing. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the ported shroud is coupled to the internal wall of the housing. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the internal volute is toroidal in shape. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the internal volute extends about the periphery of the internal wall. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments at least one of a size and contour of the first opening is selected based on a pressure distribution within the compressor. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the first opening includes a slot. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the slot extends circumferentially about the axial passageway. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the slot includes a ramped surface extending from the first end toward the second end. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the ramped surface gradually increases in distance from the first end about a circumferential of the axial passageway, the distance being measured parallel to an axis of the axial passageway. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
         FIG. 1  is a cross-sectional view of a known centrifugal compressor; 
         FIG. 2A  is a cross-sectional view of a portion of a centrifugal compressor including a ported shroud according to an embodiment; 
         FIG. 2B  is a perspective, partially cut away view of a portion of a centrifugal compressor including a ported shroud according to an embodiment; 
         FIG. 2C  is another perspective, partially cut away view of a portion of a centrifugal compressor including a ported shroud according to an embodiment; 
         FIG. 3A  is a perspective view of a ported shroud according to an embodiment; 
         FIG. 3B  is another perspective view of a ported shroud according to an embodiment; 
         FIG. 3C  is a cross-sectional view of a ported shroud according to an embodiment; and 
         FIG. 4  is a perspective view of a centrifugal compressor including a ported shroud according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
     The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof 
     Referring now to  FIG. 1 , an example of an existing centrifitgal compressor  10  is illustrated. As shown, the centrifugal compressor  10  includes a main casing  12  having an inlet  14  that directs refrigerant into a rotating impeller  16 . Although not shown, in some embodiments, the refrigerant may pass through a series of adjustable inlet guide vanes prior to reaching the impeller  16 , The impeller  16  is secured to a drive shaft  20  by any suitable means to align impeller  16  along the axis of the compressor  10 . The impeller  16  has a plurality of passages  22  formed therein that cause the incoming axial flow of a refrigerant fluid to turn in a radial direction and discharge into an adjacent diffuser section  30 . The diffuser section  30  is disposed generally circumferentially about the impeller  16  and functions to direct the compressed refrigerant fluid into a toroidal-shaped volute  32 , which directs the compressed fluid toward a compressor outlet, or alternatively, toward a second stage of the compressor  10  (not shown), depending on the configuration of the compressor. 
     With reference now to  FIGS. 2-4 , an example of a centrifugal compressor having a ported shroud according to an embodiment is illustrated. As shown, the main casing or housing  12  includes an opening  40  formed at a first end  42  thereof. The housing  12  additionally includes a wall  44  having a second end  46  arranged generally adjacent the upstream end  48  of the impeller  16 . The axial passageway  50  defined by an interior of the wall  44  fluidly couples the inlet opening  40  to the impeller  16  to direct a flow of fluid, such as refrigerant for example, to the impeller  16 . Together, the inlet opening  40  and the axial passageway  50  form the previously described inlet  14 . 
     A clearance  52  is arranged adjacent at least a portion of the internal wall  44 . In the illustrated, non-limiting embodiment, the clearance  52  is disposed concentrically with the wall  44 , for example extending between an exterior surface of the wall  44  and a surface  54  of a diffuser structure  56  that defines an outer wall of the diffuser  30 . As a result, the clearance  52  is arranged generally parallel to the axis of rotation X of the impeller  16  and shaft  20 . Further, the clearance  52  may extend from adjacent the upstream end  48  of the impeller  16  over all or a portion of the axial length of the passageway  50 . 
     In the illustrated, non-limiting embodiment, a shroud  60  is arranged in fluid communication with the clearance  52 . The shroud  60  may be integrally formed with the housing  12 , and more specifically the wall  44  of the housing  12  as shown in  FIGS. 3A-3C , or alternatively, may be a separate component configured to permanently or removably couple to the housing  12 . An inlet  62  for receiving a fluid flow is formed adjacent a first, downstream end of  64  the shroud  60 . In the illustrated embodiment, the inlet  62  includes a slot  66  that wraps about the circumference of the internal wall  44  of the housing  12 . As shown, the slot  66  is defined by a ramped surface that gradually increases in distance from the first end  64  of the shroud  60  about the circumferential length of the slot  66 . The distance is measured parallel to the axis X of impeller  16  and extends from the first end  64  of the shroud  60  towards a second, opposite end  68  of the shroud  60 . 
     An outlet  70  is formed adjacent a second, upstream end  68  of the shroud  60 . In the illustrated, non-limiting embodiment, the outlet  70  is formed as a cylindrical pipe fitting having a plurality of threads formed about an outer periphery thereof for connection with another component external  72  to the compressor  10  (see  FIG. 4 ). In an embodiment, the outlet  70  of the shroud  60  may be fluidly coupled to an evaporator. Alternatively, the outlet  70  may be coupled to a suction line (not shown) upstream from the compressor inlet  14 . A volute  74  is defined within the hollow interior of the shroud  60 , extending between inlet  62  and the outlet  70 . In an embodiment, the volute  74  may be general toroidal in shape such that the fluid flow continues to circulate about the periphery of the axial passageway  50  as the fluid travels from the inlet  62 , through the volute  74  to the outlet  70 . 
     As best shown in  FIG. 2A , when installed within the compressor  10 , the first, downstream end  64  of the shroud  60  is positioned generally adjacent the upstream end  48  of the impeller  16 . In an embodiment, the inlet  62  or slot  66  formed in the first end  64  is generally aligned with the leading edge  76  of the impeller blades  78 . In addition, the outlet  70  of the ported shroud  60  may be exposed at an exterior of the housing  12 . 
     As previously described, during operation of the compressor  10 , a flow of fluid, such as refrigerant for example, is provided to the inlet opening  40  and flows through the axial passage  50  defined by the internal wall  44  to the impeller  16 . The ported shroud  60  is operable in a plurality of modes based on the desired performance of the compressor  10 . During a first mode of operation, the ported shroud  60  may be used to reduce the flow provided to the impeller  16 . In such an outflow mode of operation, a portion of the flow provided to the impeller  16  is drawn into the inlet opening  62  from adjacent the leading edge  76  of the impeller blades  78 , thereby reducing the total amount of flow provided to the impeller  16 . The portion of the flow provided to the ported shroud  60  collects within the volute  74  before being discharged through the outlet opening  70  to another component  72 . During a second mode of operation, the ported shroud  60  may be used to increase the fluid flow provided to the impeller  16 . In an inflow mode of operation, a portion of fluid flow is provided to the outlet opening  70  for collection within the volute  74 . From the volute  74 , the fluid travels through the inlet opening  62  and is discharged adjacent the leading edge  76  of the impeller blades  78 . This flow from the ported shroud  60  is supplemental to the flow provided to the impeller  16  via the inlet opening  40  and axial passageway  50  of the housing  12 . 
     A compressor  10  including the ported shroud  60  illustrated and described herein provides the benefit of an aspirated shroud bleed on the impeller operating range, while mitigating the inlet distortion generated by the outlet of the port. 
     While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.