Patent Publication Number: US-2022228593-A1

Title: Axial and downstream compressor assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application No. 62/883,775, which was filed on Aug. 7, 2019 and is incorporated herein by reference. 
    
    
     BACKGROUND 
     The disclosure herein relates generally to a compressor assembly, and more particularly, to an axial flow compressor and a downstream compressor for a refrigeration system. 
     Rotary machines, such as compressors, are commonly used in refrigeration and turbine applications. One example of a rotary machine used in refrigeration systems 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. However, other types of compressors are also used in refrigeration systems. 
     SUMMARY 
     In one exemplary embodiment, a refrigerant compressor assembly includes an axial compressor that includes at least one axial stage. A downstream compressor is located fluidly downstream of the axial compressor and includes one of a mixed-flow impeller or a centrifugal impeller. At least one motor is in driving engagement with at least one of the axial compressor and the downstream compressor. 
     In a further embodiment of any of the above, the at least one axial stage is a vaned stage that includes a rotor and a stator. 
     In a further embodiment of any of the above, the axial compressor includes at least one axial stage. 
     In a further embodiment of any of the above, a transmission mechanically connects the at least one axial stage and the at least one motor. 
     In a further embodiment of any of the above, the at least one axial stage includes a first vaneless stage immediately upstream of a second vaneless stage. 
     In a further embodiment of any of the above, the first vaneless stage is configured to rotate in a first rotational direction. The second vaneless stage is configured to rotate in a second rotational direction. 
     In a further embodiment of any of the above, that at least one motor includes a first motor for driving the first vaneless stage and a second motor for driving the second vaneless stage. 
     In a further embodiment of any of the above, the second motor drives the downstream compressor. 
     In a further embodiment of any of the above, the downstream compressor is a mixed-flow compressor. The mixed-flow impeller includes a hub and a plurality of impeller blades that extend outward from the hub. 
     In a further embodiment of any of the above, the mixed-flow compressor includes a diffusor downstream of the mixed-flow impeller. 
     In a further embodiment of any of the above, the diffuser includes at least one row of circumferentially spaced diffuser vanes. 
     In a further embodiment of any of the above, the diffuser includes a first row of circumferentially spaced diffuser vanes. A second row of circumferentially space diffuser vanes are located axially downstream of the first row of circumferentially spaced diffuser vanes. 
     In another exemplary embodiment, a method of operating a refrigerant compressor assembly includes the step of compressing a refrigerant with an axial compressor including at least one axial stage. The refrigerant is compressed with a downstream compressor located fluidly downstream of the axial compressor. The downstream compressor includes one of a mixed-flow impeller or a centrifugal impeller. 
     In a further embodiment of any of the above, the axial compressor includes at least a first vaneless stage and a second vaneless stage. 
     In a further embodiment of any of the above, the method includes driving the first vaneless stage in a first rotational direction with a first motor. The second vaneless stage is driven in a second rotational direction with a second motor. 
     In a further embodiment of any of the above, the downstream compressor is driven by the second motor. 
     In a further embodiment of any of the above, the downstream compressor is a mixed-flow compressor. The refrigerant exiting the mixed-flow impeller is diffused with a diffuser. 
     In a further embodiment of any of the above, the diffuser includes at least one row of circumferentially spaced diffuser vanes. 
     In a further embodiment of any of the above, a first axial stage of the at least one axial stage compresses the refrigerant with a pressure ratio of 1.2 to 2.0. 
     In a further embodiment of any of the above, the downstream compressor compresses the refrigerant with a pressure ratio of 2.0 to 6.5. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  schematically illustrates an example compression assembly for use in a refrigeration system. 
         FIG. 1B  schematically illustrates another example compression assembly for use in the refrigerant system. 
         FIG. 1C  schematically illustrates yet another example compression assembly for use in the refrigeration system. 
         FIG. 2A  schematically illustrates an example axial compressor for use with the compressor assembly of  FIG. 1A . 
         FIG. 2B  schematically illustrates an example axial compressor for use with the compressor assembly of  FIG. 1B . 
         FIG. 2C  schematically illustrates another example axial compressor for use with the compressor assembly of  FIG. 1C . 
         FIG. 3  illustrates an example mixed-flow compressor. 
         FIG. 4A  illustrates a front perspective view of an impeller of the mixed-flow compressor of  FIG. 3 . 
         FIG. 4B  is a cross-sectional view of the impeller of  FIG. 4A . 
         FIG. 5  illustrates an example diffuser in the mixed-flow compressor of  FIG. 4 . 
         FIG. 6  illustrates an example centrifugal compressor. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1A  schematically illustrates an example compressor assembly  20 A for use in a refrigeration system. In the illustrated example, the compressor assembly  20 A includes an axial compressor  22  fluidly upstream of a downstream compressor  24 , such as a mixed-flow compressor or a centrifugal compressor. A motor  26  directly drives the downstream compressor  24  through a driveshaft  28  and the motor  26  drives the axial compressor  22  through the driveshaft  28  connected to a transmission  30 . In particular, the transmission  30  includes an input connected to the driveshaft  28  and an output connected to an axial driveshaft  32 , which is mechanically coupled to the axial compressor  22 . However, the driveshaft  28  could directly drive the axial compressor  22  without the use of the transmission  30  such that the axial compressor  22  and the downstream compressor  24  rotate in the same direction and at the same speed. 
     During operation of the compressor assembly  20 A, refrigerant R is drawn into an inlet  34  on the axial compressor  22 . Once the refrigerant R is compressed by the axial compressor  22 , the refrigerant R travels through an outlet  36  on the axial compressor  22 . From the outlet  36 , the refrigerant R is directed to an inlet  38  on the downstream compressor  24  where the refrigerant R is further compressed in the downstream compressor  24  before being discharged through an outlet  40  on the downstream compressor  24 . In the illustrated example, the axial compressor  22  includes a pressure ratio of 1.2 to 2.0 per stage and the downstream compressor  24  includes a pressure ratio of 2.0 to 6.5. Axial compressors can include vaned stages with a rotor and a stator forming a single stage as described below in relation to  FIGS. 2A and 2B  or vaneless stages without stators separating adjacent rotors as described below in relation to  FIG. 2C . 
       FIG. 1B  illustrates another example compressor assembly  20 B similar to the compressor assembly  20 A except where described below or shown in the Figures. The compressor assembly  20 B includes a motor  27  driving the axial compressor  22 B independently from the motor  26 , which drives the downstream compressor  24 . In the illustrated example, the motor  27  turns a drive shaft  29 , which is mechanically coupled to the axial compressor  22 B. 
     During operation of the compressor assembly  20 B, the refrigerant R is drawn into the inlet  34  on the axial compressor  22 B. Once the refrigerant R is compressed by the axial compressor  22 B, the refrigerant R then travels through the outlet  36  on the axial compressor  22 B. From the outlet  36 , the refrigerant R is directed to the inlet  38  on the downstream compressor  24  where the refrigerant R is compressed in the downstream compressor  24  before being discharged through the outlet  40  on the downstream compressor  24 . 
       FIG. 1C  illustrates another example compressor assembly  20 C similar to the compressor assembly  20 B except where described below or shown in the Figures. The compressor assembly  20 C includes the motor  27  for driving an upstream stage  50 C in the axial compressor  22 C through the driveshaft  29  while the motor  26  drives a downstream stage  54 C of the axial compressor  22 C and the downstream compressor  24  through the driveshaft  28  ( FIG. 2C ) and the motor  26 . In the illustrated example, the driveshaft  29  and the driveshaft  28  could rotate in opposite directions. 
     During operation of the compressor assembly  20 A, the refrigerant R is drawn into the inlet  34  on the axial compressor  22 C. Once the refrigerant R is compressed by the axial compressor  22 C, the refrigerant R then travels through the outlet  36  on the axial compressor  22 C. From the outlet  36 , the refrigerant R is directed to the inlet  38  on the downstream compressor  24  where the refrigerant R is compressed in the downstream compressor  24  before being discharged through the outlet  40  on the downstream compressor  24 . 
       FIG. 2A  illustrates an example configuration of the axial compressor  22  with the transmission  30  shown in  FIG. 1A . As shown in  FIG. 2A , the axial compressor  22  includes a first vaned stage  50  and a second vaned stage  54 . The first vaned stage  50  includes a set of circumferentially spaced rotor blades  52  defining a rotor and set of circumferentially spaced vanes  60  defining a stator. The second vaned stage  54  includes a set of circumferentially spaced rotor blades  56  defining a rotor and a set of circumferentially spaced vanes  64  defining a stator. Although the illustrated example shows two vaned stages  50 ,  54 , the axial compressor  22  could include a single vaned stage or more than two vaned stages, such as three to five stages. 
     In the illustrated example, the transmission  30  may reverse the rotational direction and/or change the rotational speed of the drive shaft  28  such that the drive shaft  28  and the axial drive shaft  32  rotate in the same or opposite directions with equal or differing speeds. In one example, the transmission  30  is a constant ratio transmission and in another example, the transmission  30  is a variable ratio transmission. However, as discussed above, the transmission  30  could be eliminated such that the driveshaft  28  directly drives the axial compressor  22  without the axial drive shaft  32 . 
     In the illustrated example, the rotor blades  52  are located at the inlet  34  and the vanes  64  are located at the outlet  36 . The axial drive shaft  32  engages both the first and second vaned stages  50 ,  54  to drive the rotor blades  52 ,  56  in the same rotational direction and at the same speed about the axis of rotation A. Additionally, the axis of rotation A of the axial compressor  22  is coaxial with the axis of rotation X 1  of the drive shaft  28 . However, the axis of rotation A and the axis of rotation X 1  could be parallel and not coaxial or the axis of rotation A could be transverse to the axis of rotation X 1 . 
       FIG. 2B  illustrates the axial compressor  22 B located in the compressor assembly  20 B and the motor  27  located on an upstream side of the axial compressor  22 B. In the illustrated example, the motor  27  rotates the drive shaft  29  about an axis of rotation X 2  to drive the axial compressor  22 B independently from the motor  26  driving the downstream compressor  24 . 
       FIG. 2C  illustrates another example configuration of an axial compressor  22 C similar to the axial compressor  22  except where described below or shown in the Figures. The axial compressor  22 C includes a first vaneless stage  50 C having a set of circumferentially spaced rotor blades  52 C and a second vaneless stage  54 C having a set of circumferentially spaced rotor blades  56 C. The first vaneless stage  50 C is immediately adjacent the second vaneless  54 C such that as the refrigerant R passes over the rotor blades  52 C, the refrigerant R will immediately reach the rotor blades  56 C. Additionally, the first and second vaneless stages  50 C,  54 C rotate in opposite rotational directions with the first vaneless stage  50 C being driven by the motor  27  through the drive shaft  29  and the second vaneless stage  54 C being driven by the motor  26  through the driveshaft  28 . The axial compressor  22 C could also contain more than two vaneless stages. 
       FIG. 3  illustrates one example of the downstream compressor  24 , such as a mixed-flow compressor  24 A attached to the motor  26 . In the illustrated example, the mixed-flow compressor  24 A includes a main casing or housing  42  that at least partially defines the inlet  38  into the mixed-flow compressor  24 A for receiving refrigerant and the outlet  40  for discharging the refrigerant R from the mixed-flow compressor  24 A. The mixed-flow compressor  24 A draws the refrigerant R towards the inlet  38  by rotating a mixed-flow impeller  46  immediately downstream of the inlet  38 . The impeller  46  then directs the refrigerant R to a diffuser section  44  located axially downstream of the impeller  46 . 
     The diffuser section  44  includes a diffuser  45  ( FIG. 5 ) with a hub  65  with a first row of circumferential vanes  66  and a second row of vanes  68  extending radially outward from a radially outer surface of the hub  65 . The hub  65  forms a fluid passageway  70  with a portion of the housing  42  to direct the refrigerant R into a volute  72  before being redirected from the axial direction to a radial direction outward toward the outlet  40  of the mixed-flow compressor  24 A. 
     The mixed-flow compressor  24 A is driven by the motor  26  connected to the impeller  46 . In the illustrated example, the motor  26  includes a stator  74  attached to a portion of the housing  42  that surrounds a rotor  76  attached to the drive shaft  28 . The drive shaft  28  is configured to rotate about the rotational axis X 1 . The axis of rotation X 1  is common with the impeller  46 , the rotor  76 , and the drive shaft  28  and is common with a central longitudinal axis extending through the housing  42 . 
     As shown in  FIGS. 4A and 4B , the impeller  46  includes a hub or body  78  having a front side  80  and back side  82 . As shown, the diameter of the front side  80  of the body  78  generally increases toward the back side  82 , such that the impeller  46  is generally conical in shape. A plurality of blades  84  extend radially outward from the body  78  relative to the axis of rotation X 1 . Each of the plurality of blades  84  is arranged at an angle to the axis of rotation X 1  of the drive shaft  28 . In one example, each of the blades  84  extends between the front side  80  and the back side  82  of the impeller  46 . As shown, each of the blades  84  includes an upstream end  86  adjacent the front side  80  and a downstream end  88  adjacent the back side  82 . Further, the downstream end  88  of the blade  84  is circumferentially offset from the corresponding upstream end  86  of the blade  84 . 
     A plurality of passages  90  is defined between adjacent blades  84  to discharge a fluid passing over the impeller  46  generally parallel to the axis X 1 . As the impeller  46  rotates, fluid approaches the front side  80  of the impeller  46  in a substantially axial direction and flows through the passages  90  defined between adjacent blades  84 . Because the passages  90  have both an axial and radial component, the axial flow provided to the front side  80  of the impeller  46  simultaneously moves both parallel to and circumferentially about the axis X 1  of the drive shaft  28 . In combination, an inner surface  92  (shown in  FIG. 4 ) of the housing  42  and the passages  90  of the impeller  46  cooperate to discharge the compressed refrigerant R from the impeller  46  to the diffuser section  44 . In one example, the compressed refrigerant is discharged from the impeller  46  at an angle relative to the axis X 1  of the drive shaft  28  into the diffuser section  44 . 
       FIG. 6  illustrates another example downstream compressor  24 , such as a centrifugal compressor  24 B. As shown, the centrifugal compressor  24 B includes a main casing  94  having the inlet  38  that directs the refrigerant R into a rotating centrifugal impeller  96  through a series of adjustable inlet guide vanes  98 . The impeller  96  is secured to the drive shaft  28  by any suitable means to align impeller  96  along the axis X 1  of the centrifugal compressor  24 B and driven by the motor  26 . The impeller  96  has a plurality of passages  100  formed therein that cause the incoming axial flow of the refrigerant to turn in a radial direction and discharge into an adjacent diffuser section  102 . The diffuser section  102  is disposed generally circumferentially about the impeller  96  and functions to direct the compressed refrigerant R into the outlet  40 . 
     Although the different non-limiting examples are illustrated as having specific components, the examples of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting examples in combination with features or components from any of the other non-limiting examples. 
     It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed and illustrated in these exemplary examples, other arrangements could also benefit from the teachings of this disclosure. 
     The foregoing description shall be interpreted as illustrative and not in any limiting sense. A worker of ordinary skill in the art would understand that certain modifications could come within the scope of this disclosure. For these reasons, the following claim should be studied to determine the true scope and content of this disclosure.