Patent Publication Number: US-2023151824-A1

Title: Multistage compressor with swirl-reducing ribs

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. Provisional Application No. 63/278,633, which was filed on Nov. 12, 2021. 
    
    
     BACKGROUND 
     Compressors have various uses including, for example, refrigerant circuits useful for refrigeration or air conditioning. A variety of compressor designs are available. One type of compressor is referred to as a multistage compressor because it includes a first compressor stage upstream of a second compressor stage. Multistage compressors can introduce efficiencies and capabilities that exceed those of single-stage compressors. Even with the advantages a multistage compressor can provide, there are issues associated with fluid flow within the compressor especially between the first and second stages. 
     SUMMARY 
     An illustrative example embodiment of a multistage compressor includes a first compressor stage, a second compressor stage downstream of the first compressor stage, and a motor section between the first compressor stage and the second compressor stage. The motor section includes a housing and a motor within the housing. A space between the motor and the housing establishes a flow path for fluid to flow from the first compressor stage to the second compressor stage. A plurality of ribs within the space have a curvature along at least a portion of a length of the ribs that changes a direction of fluid flow within the space such that the fluid flows downstream of the curvature in a direction parallel to a longitudinal axis of the housing. 
     In addition to one or more of the features described above, or as an alternative, the plurality of ribs respectively include a first portion and a second portion; the second portion is downstream of the first portion; the first portion has the curvature; and the second portion is parallel to the longitudinal axis. 
     In addition to one or more of the features described above, or as an alternative, the first compressor section forces fluid into the space along a trajectory that is at an oblique angle relative to the longitudinal axis of the housing; and the first portions of the ribs have a first segment situated at the oblique angle relative to the longitudinal axis. 
     In addition to one or more of the features described above, or as an alternative, the curvature of the first portion is configured to provide a smooth transition between the first segment and a terminal segment of the second portion. 
     In addition to one or more of the features described above, or as an alternative, the ribs at least partially extend between an interior of the housing and an exterior of the motor such that the ribs support the motor within the housing. 
     In addition to one or more of the features described above, or as an alternative, the plurality of ribs are equally spaced from each other in a circumferential direction. 
     In addition to one or more of the features described above, or as an alternative, the motor includes a rotor that rotates about the longitudinal axis. 
     An illustrative example embodiment of a method is for controlling fluid flow in a multistage compressor including a first compressor stage, a second compressor stage downstream of the first compressor stage, a housing between the first compressor stage and the second compressor stage, and a motor in the housing. The method includes directing fluid from the first compressor stage into a space between the housing and the motor; changing a direction of fluid within the space using a plurality of ribs within the space that include a curvature along at least a portion of a length of the ribs; and directing fluid flow downstream of the curvature in a direction parallel to a longitudinal axis of the housing. 
     In addition to one or more of the features described above, or as an alternative, the plurality of ribs respectively include a first portion and a second portion; the second portion is downstream of the first portion; the first portion has the curvature; and the second portion is parallel to the longitudinal axis. 
     In addition to one or more of the features described above, or as an alternative, the first compressor section forces fluid into the space along a trajectory that is at an oblique angle relative to the longitudinal axis of the housing; and the first portions of the ribs have a first segment situated at the oblique angle relative to the longitudinal axis. 
     In addition to one or more of the features described above, or as an alternative, the curvature of the first portion is configured to provide a smooth transition between the first segment and a terminal segment of the second portion. 
     In addition to one or more of the features described above, or as an alternative, the ribs at least partially extend between an interior of the housing and an exterior of the motor such that the ribs support the motor within the housing. 
     In addition to one or more of the features described above, or as an alternative, the plurality of ribs are equally spaced from each other in a circumferential direction. 
     In addition to one or more of the features described above, or as an alternative, the motor includes a rotor that rotates about the longitudinal axis. 
     The various features and advantages of at least one disclosed example embodiment will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    shows an example embodiment of a multistage compressor. 
         FIG.  2    shows an example configuration of ribs that support a motor within a housing of the multistage compressor of  FIG.  1   . 
         FIG.  3    schematically illustrates an example fluid flow pattern established by the ribs shown in  FIG.  2   . 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    schematically shows a multistage compressor  20  that includes a first compressor stage  22  and a second compressor stage  24  downstream of the first compressor stage  22 . A motor  26 , which causes rotation of rotating components of the compressor stages  22 ,  24  is situated between the first compressor stage  22  and the second compressor stage  24 . 
     A housing  28  contains the motor  26  and is coupled with the compressor stages  22 ,  24 . A plurality of ribs  30  extend in a radial direction from an inside of the housing  28  toward an exterior of the motor  26 . In the illustrated example embodiment, the ribs  30  contact the exterior of the motor  26  and support the motor  26  within the housing  28 . The ribs  30  have a height that corresponds to a difference between an outside dimension of the motor  26  and an inside dimension of the corresponding portion of the housing  28  along at least some of the length of the ribs. In some embodiments, the entire length of the ribs  30  corresponds to the radial distance between the interior of the housing  28  and the exterior of the motor  26 . 
     The difference between the interior diameter or dimension of the housing  28  and the exterior of the motor  26  leaves a space  32  between the inside of the housing  28  and the outside or exterior of the motor  26 . The space  32  provides a fluid flow path for fluid to flow from the first compressor stage  22  to the second compressor stage  24 . The ribs  30  are equally spaced in a circumferential direction about the inside of the housing  28 . The openings or spaces between the ribs  30  establish channels for the fluid to flow into and through the space  32 . 
     The ribs  30  direct fluid flow through the space  32  in a manner that increases the efficiency of the multistage compressor  20 . The ribs  30  each include a curvature along at least some of the length of the rib  30 . The curvature of the ribs  30  changes a direction of fluid flow within the space  32  such that fluid downstream of the ribs  30  flows in a direction parallel to a longitudinal axis  34  of the housing  28 . 
     As shown in  FIG.  2   , the ribs  30  respectively include a first portion  40  and a second portion  42 . The first portions  40  in this example embodiment include the curvature as shown at  44 . At least some of the second portion  42  in the illustrated example is oriented parallel to the longitudinal axis  34 . In the illustrated example, the most downstream end of the ribs  30  are approximately parallel to the axis  34 . The first compressor stage directs fluid into the space  32  along a trajectory that is at an oblique angle  46  relative to the longitudinal axis  34 . This trajectory is the result of the operation of an impeller  48  and diffuser  50  of the first compressor stage. 
     The first portions  40  of the ribs  30  are at least partially oriented at approximately the oblique angle  46  relative to the axis  34 . The curvatures  44  change the trajectory of the fluid and the second portions  42  guide or direct the fluid flow in a direction parallel to the axis  34 . 
     With the ribs  30 , fluid flowing through the space  30  follows a path or trajectory  52  like that schematically shown in  FIG.  3   . Without the ribs  30 , the fluid flow along the entire length of the space  30  would include swirl. The fluid flow would follow a swirling or generally helical path. By changing the direction of the path  52  from a swirling or helical pattern to one that is parallel to the axis  34 , the ribs  30  improve the efficiency of the multistage compressor  20 . 
     Reducing or eliminating swirl along the space  32  reduces the wetted area and frictional losses as the fluid flows toward the second stage  24 . This increases efficiency and allows for shortening the length of the multistage compressor  20 , which allows for additional economic advantages. The configuration of the ribs  30  also eliminates any profile losses that may otherwise be caused by motor supporting ribs that are not aligned with the flow velocity direction. 
     Embodiments of this invention include ribs  30  that reduce or eliminate swirl of the fluid flowing downstream of the first compressor stage  22  through the space  32  toward the second compressor stage  24 . The exact configuration of the ribs  30  may vary and those skilled in the art who have the benefit of this description will realize how to customize ribs consistent with those discussed above and shown in the drawings to meet the needs of their particular compressor design. 
     The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.