Patent Publication Number: US-10330105-B2

Title: Compressor including flow control insert and electromagnetic actuator

Description:
BACKGROUND 
     Centrifugal refrigerant compressors are known, and include one or more impellers driven by a motor. During operation of a centrifugal compressor, refrigerant is expelled outward from the impeller. One known compressor type includes a vaneless diffuser configured to regulate the flow of fluid expelled by the impeller. Another known compressor type includes a vaned diffuser. Vaned diffusers are known to include mechanical and/or hydraulic actuators capable of either turning the diffuser vanes or moving a sidewall relative to the diffuser. 
     SUMMARY 
     One exemplary embodiment of this disclosure relates to a centrifugal compressor. The compressor includes an impeller, an electromagnetic actuator, and a flow control insert. The flow control insert is selectively moveable in response to the electromagnetic actuator to regulate a flow of fluid expelled by the impeller. 
     Another exemplary embodiment of this disclosure relates to a method for regulating a flow of fluid. The method includes expelling a flow of fluid from an impeller, and positioning a flow control insert in response to an electromagnetic actuator to regulate the flow of fluid expelled by the impeller. 
     These and other features of the present disclosure can be best understood from the following drawings and detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings can be briefly described as follows: 
         FIG. 1  is a highly schematic view of a refrigeration system. 
         FIG. 2  schematically illustrates the electromagnetic actuator of  FIG. 1 . 
         FIG. 3A  illustrates an example vaned diffuser. 
         FIG. 3B  illustrates an example flow control insert. 
         FIG. 3C  illustrates the vaned diffuser of  FIG. 3A  and the flow control insert of  FIG. 3B . 
         FIG. 4  illustrates an example permanent magnet array. 
         FIGS. 5A-5C  schematically illustrate alternative electromagnetic actuator arrangements. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  schematically illustrates an example refrigeration system  10 . In the example, the refrigeration system  10  includes a centrifugal refrigerant compressor  12  for circulating a refrigerant. The compressor  12  includes a housing  14  within which an electric motor  16  is arranged. In one example, the electric motor  16  includes a stator  18  arranged radially outside of a rotor  20 . The rotor  20  is mechanically coupled to a rotor shaft  22 , which rotates about an axis X to drive an impeller  24  to compress refrigerant. Although only one impeller  24  is shown, this disclosure may be used in connection with compressors having more than one impeller. Further, while a refrigeration system  10  is illustrated, it should be understood that this disclosure applies to other systems. 
     The compressor  12  is in fluid communication with a refrigeration loop L. While not illustrated, refrigeration loops, such as the refrigeration loop L, are known to include a condenser, an evaporator, and an expansion device. 
     During operation of the compressor  12 , refrigerant enters the impeller  24  through an inlet end  24 I, and is expelled radially outward from an outlet end  24 O thereof. Downstream of the outlet end  24 O, the refrigerant passes through a throat  26 , and ultimately back to the refrigerant loop L. It should be understood that the throat  26  may include a diffuser  27  ( FIG. 3A ) in at least one example. In this example, the diffuser  27  includes a plurality diffuser vanes  27 V. 
     A moveable flow control insert  28  is positioned radially downstream of the outlet end  24 O of the impeller  24 , and is moveable to selectively regulate a flow of fluid expelled from the impeller  24 . In this example, the flow control insert  28  is moveable by way of an electromagnetic actuator  30  in a generally axial direction A, which is substantially parallel to the axis of rotation X of the impeller  24 . In the example where a vaned diffuser  27  is included in the throat  26 , the flow control insert  28  would include projections  28 P ( FIG. 3B ) corresponding to spaces S ( FIG. 3C ) between adjacent diffuser vanes  27 V. The projections  28 P in this example axially move in-and-out of spaces S between adjacent diffuser vanes  27 V (e.g., as illustrated in  FIG. 3C ). 
     The electromagnetic actuator  30  is controlled by a control  32 . The control  32  is an electronic control, and, as is known in the art, is capable of being programmed to perform numerous functions, including sending instructions to control various components of a system. In one example, the control  32  is in communication with two separate circuits. One circuit is a control circuit, which is very low voltage (signal). Another circuit is a power circuit which carries current and higher voltage (e.g., 250 VDC). 
     In the illustrated example, the control  32  is in communication with position sensor  34 A (e.g., via the control circuit) configured to detect the relative position of the flow control insert  28  relative to the throat  26 , by sensing a distance between the position sensor  34 A and a sensor target  34 B mounted to the flow control insert. In this example, the control  32  uses information from the position sensor  34 A to control the force generated by the electromagnetic actuator  30  by controlling the electric current flowing to the coil  44 . The position sensor  34 A and sensor target  34 B are optional, however, and the control  32  can use other information (such as a pressure differential) indicative of the position of the flow control insert  28  when instructing the electromagnetic actuator  30 . The position sensor components  34 A can be any known component configured to generate a signal (capable of being interpreted by the control  32 ) corresponding to a distance between the position sensor  34 A and sensor target  34 B. The control  32  is further in communication with a variable voltage or current source (not shown), in order to provide a desired level of electric current to the electromagnetic actuator  30 , as will be discussed below. 
       FIG. 2  illustrates the detail of the electromagnetic actuator  30 . In this example, the electromagnetic actuator  30  includes an electromagnet  36  and first and second permanent magnets  38 ,  40 . The electromagnet  36  includes a core  42  and a coil  44  arranged within the core  42 . The control  32  is configured to provide a variable level of electric current to the coil  44  (e.g., via the power circuit). Depending on the level of electric current flowing through the coil  44 , the magnetic field generated by the electromagnet  36  varies. The permanent magnets  38 ,  40 , on the other hand, generate a substantially constant magnetic field. 
     It should be understood that while  FIGS. 1 and 2  only illustrate a partial sectional view of this disclosure, the electromagnet  36  can be configured to continuously extend circumferentially around the axis of rotation X. Sets of the first and second permanent magnets  38 ,  40  in one example are circumferentially spaced 90° apart relative to the axis of rotation X. In another example, sets of the permanent magnets  38 ,  40  are circumferentially spaced 120° apart. The sets of permanent magnets  38 ,  40  may be spaced at any angle, however in some examples it is important to equally space the permanent magnets about the axis of rotation X. 
     In this example, the first permanent magnet  38  is mounted to the housing and is stationary relative to the flow control insert  28 . The second permanent magnet  40  is moveable with the flow control insert  28 . The first permanent magnet  38  is arranged to generate a first magnetic field vector V 1  which is generally opposite to the magnetic field vector V 2  generated by the second permanent magnet  40 . This results in a repulsion force F R  between the first and second permanent magnets  38 ,  40 , which biases the flow control insert in a direction D 2  toward the throat area  26 , and away from the electromagnetic actuator  30 . 
     The control  32  is configured to provide a flow of electric current to the coil  44  to generate an attraction force F A  which attracts the flow control insert  28  in a direction D 1 , against the repulsion force F R  of the first and second permanent magnets  38 ,  40 . The control  32  can thus vary the level of electric current flowing through the coil  44  to selectively adjust the position of the flow control insert  28 . 
     In an open position, the control  32  provides a flow of electric current through the coil  44  that results in an attraction force F A  that substantially overcomes the repulsion force F R  to move the flow control insert  28  to a position where flow in the throat area  26  is substantially uninhibited by the flow control insert  28 . In a closed position on the other hand, the control  32  essentially provides no current to the coil  44 , and thus the flow control insert  28  will be under the influence of repulsion force F R  and will move to substantially block the throat area  26 . The control  32  can further provide a level of electric current to the coil  44  to position the flow control insert  28  at any number of intermediate positions axially between the open and closed positions, wherein flow in the throat area  26  is partially blocked. 
     In the closed position, in one example, the flow control insert  28  essentially reduces the throat area  26  by 80% relative to the open position. In another example, the flow control insert  28  reduces the throat area  26  by 50% relative to the open position. This number may vary as needed, and depending on the selected contour of the flow control insert  28 . 
     In the example of  FIGS. 1 and 2 , the flow control insert  28  is attached to a moving target structure, which in this example is a disk,  35 , which is used to support the second permanent magnet  40  and the flow control insert  28 . While not illustrated, the moving target structure  35  may move along axial guides arranged relative to the housing  14 . In one example, the sensor target  34 B attached to this moving target structure  35 , as is the second permanent magnet  40 . However, in other examples, there is no moving target structure  35 , and the sensor target  34 B and second permanent magnet  40  can be directly attached to the flow control insert  28 . In this example, the moving target  35  is a magnetic structure that is responsive to the magnetic field created by the electromagnet  36 . In the example without a moving target structure  35 , the flow control insert  28  would be at least partially magnetic and thus be configured to respond to the magnetic field created by the electromagnet  36 . 
     This disclosure may be particularly beneficial when used in refrigerant compressors, and other types hermetically sealed working environments. In part, this is because there are no mechanical components required to adjust the position of the flow control insert  28 . Thus, the flow of fluid expelled by the impeller  24  can be regulated without the need to monitor and maintain mechanical components, which in turn increases the efficiency and reliability of the system. This disclosure further simplifies the prior systems (which include various mechanical and/or hydraulic components) by reducing the number of moving components. Further still, this disclosure increases the stable operating range of the compressor (relative to compressors including vaneless diffusers) while preserving the increased pressure recovery and resulting overall efficiency attributed to vaned diffusers. 
       FIG. 4  schematically illustrates an example wherein the first permanent magnet  38  includes a semi-Halbach array (or, partial Halbach array) of permanent magnets  38   a - 38   d . It should be understood that the second permanent magnet  40  includes a similar arrangement in one example, in such a way that the resulting magnetic flux is in an opposite direction than the magnetic flux of the first permanent magnet  38 . As is known in the art, Halbach arrays are arrangements of permanent magnets that augments the magnetic field on one side of the array while cancelling the field to near zero on the other side. In this example, the outer permanent magnets  38   a  and  38   d  generate a magnetic flux along circumferential vectors VRA, VRD, toward the inner permanent magnets  38   b  and  38   c . This concentrates the magnetic flux between the magnets  38   a - 38   d , and increases (e.g., augments) the magnetic flux created by the middle magnets  38   b  and  38   c  along the vector V 1 . This in turn maximizes the repulsion force FR. 
       FIGS. 5A-5C  illustrate three alternate electromagnetic actuator arrangements. In a first example, in  FIG. 5A , two sets of permanent magnets  38 ,  40  are included on radially opposite sides of the electromagnet  36 . In the example of  FIG. 5B , two electromagnets  36  are provided, and are positioned on radially opposite sides of the first and second permanent magnets  38 ,  40 . The example of  FIG. 5C  also includes two electromagnets  36 , however these electromagnets  36  are provided on opposite axial sides of the moving target structure  35 . One skilled in this art can select an appropriate actuator arrangement. 
     Although the different examples have the specific components shown in the illustrations, embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples. 
     One of ordinary skill in this art would understand that the above-described embodiments are exemplary and non-limiting. That is, modifications of this disclosure would come within the scope of the claims. Accordingly, the following claims should be studied to determine their true scope and content.