Patent Publication Number: US-2023139727-A1

Title: Compressor interstage throttle, and method of operating therof

Description:
FIELD 
     This disclosure relates generally to a centrifugal compressor. More specifically, this disclosure relates to an interstage throttle used in a multistage centrifugal compressor in a heating, ventilation, air conditioning, and refrigeration (HVACR) system. 
     BACKGROUND 
     A compressor can include multiple stages in series for compressing a working fluid. A centrifugal compressor can include an impeller in each of its stages for compressing the working fluid. For example, working fluid is compressed in a first stage, flows from the first stage to a second stage, and is then further compressed in the second stage to a higher pressure. A centrifugal compressor can be configured to guide the working fluid discharged from the first stage to the second stage. HVACR systems are generally used to heat, cool, and/or ventilate an enclosed space (e.g., an interior space of a commercial building or a residential building, an interior space of a refrigerated transport unit, or the like). A HVACR system can include a heat transfer circuit with a compressor configured to compress a working fluid flowing through the heat transfer circuit. 
     BRIEF SUMMARY 
     In an embodiment, an interstage throttle for a centrifugal compressor includes a flow guide plate, a throttle ring with teeth, a drive ring, and linkage assemblies. The flow guide plate includes a plurality of guide vanes that forms channels extending radially inward. The channels are configured to direct working fluid discharged from a first stage of the centrifugal compressor to an inlet of a second stage of the centrifugal compressor. The linkage assemblies connect the drive ring to the throttle ring such that rotation of the drive ring moves the throttle ring in an axial direction relative to the flow guide plate between a retracted position and an extended position. In the extended position, the teeth of the throttle ring are disposed in and partially block the channels. 
     In an embodiment, the teeth of the throttle ring block less of the channels in the retracted position than in the extended position. 
     In an embodiment, the throttle ring includes radial shafts and each of the linkage assemblies include pairs of a drive linkage and a support linkage connected to the radial shafts of the throttle ring. The drive linkage and the support linkage in each of the pairs are connected to the same respective one of the radial shafts on the throttle ring. 
     In an embodiment, the centrifugal compressing includes a housing. The flow guide plate, the throttle ring, and the drive ring are disposed within the housing. The drive linkages connect the drive ring to the throttle ring and are configured to transfer rotation of the drive ring into axial movement of the throttle ring. The support linkages connect the throttle ring to the housing and are configured to prevent rotation of the throttle ring. 
     In an embodiment, in each pair of drive linkage and support linkage, the drive linkage has a first end rotatably connected to the respective radial shaft on the throttle ring and a second end rotatably connected to a respective radial shaft on the drive ring. 
     In an embodiment, in each pair of drive linkage and support linkage, the support linkage has a first end connected to the respective radial shaft on the throttle ring and a second end connected to the housing of the interstage throttle. 
     In an embodiment, the centrifugal compressor includes an actuator and an actuation linkage assembly. The actuation linkage assembly connects the actuator to the drive ring. Extending of the actuator causes rotation of the drive ring. The retraction of the actuator causes an opposite rotation of the drive ring. 
     In an embodiment, the rotation of the throttle ring from the retracted position to the extended position is less than 5 degrees. 
     In an embodiment, the flow guide plate has a fixed position in the interstage throttle. 
     In an embodiment, a method of operating a centrifugal compressor includes compressing a working fluid to a first pressure in the first stage, and directing the working fluid discharged from the first stage to a second stage via channels in a interstage throttle. The interstage throttle includes a flow guide plate with a plurality of guide vanes. The guide vanes form the channels which extend radially inward. The interstage throttle also includes a throttle ring, a drive ring, and linkage assemblies that connect the drive ring to the throttle ring. The directing of the working fluid via the channels includes rotating the drive ring which moves the throttle ring in an axial direction relative to the flow guide plate between a retracted position and an extended position. The throttle ring in the extended position having teeth disposed in and partially blocking the channels. 
     In an embodiment, the method also includes further compressing the working fluid in the second stage from the first pressure to a second pressure. 
     In an embodiment, the rotating of the drive ring includes extending or retracting an actuator connected to the drive ring, the extending or retracting of the actuator causing the rotation of the drive ring. 
     In an embodiment, a centrifugal compressor includes a first stage, a second stage, and an interstage throttle fluidly connecting the first stage to the second stage. The first stage includes a first impeller configured to compress working fluid to a first pressure. The second stages a second impeller configured to compress the working fluid to a second pressure. The interstage throttle includes a flow guide plate, a throttle ring with teeth, a drive ring, and linkage assemblies. The flow guide plate includes a plurality of guide vanes that forms channels extending radially inward. The channels configured to direct working fluid discharged from a first stage of the centrifugal compressor to an inlet of a second stage of the centrifugal compressor. The linkage assemblies connect the drive ring to the throttle ring such that rotation of the drive ring moves the throttle ring in an axial direction relative to the flow guide plate between a retracted position and an extended position. In the extended position, the teeth of the throttle ring are disposed in and partially block the channels. 
     In an embodiment, the teeth of the throttle ring block less of the channels in the retracted position than in the extended position. 
     In an embodiment, the throttle ring includes radial shafts, each of the linkage assemblies include pairs of a drive linkage and a support linkage connected to the radial shafts of the throttle ring. The drive linkage and the support linkage in each of the pairs are connected to the same respective one of the radial shafts on the throttle ring. 
     In an embodiment, the centrifugal compressor also includes a housing. The flow guide plate, the throttle ring, and the drive ring are disposed within the housing. The drive linkages connect the drive ring to the throttle ring and are configured to transfer rotation of the drive ring into axial movement of the throttle ring. The support linkages connect the throttle ring to the housing and are configured to prevent rotation of the throttle ring. 
     In an embodiment, the centrifugal compressor also includes an actuator and an actuation linkage assembly connecting the actuator to the drive ring. Extending the actuator causes rotation of the drive ring, and retraction of the actuator causes the opposite rotation of the drive ring. 
     In an embodiment, the centrifugal compressor includes a housing. The flow guide plate, the throttle ring, and the drive ring are disposed within the housing. The actuator is external to the housing and the actuation linkage assembly extends through the housing. 
     In an embodiment, the rotation of the throttle ring from the retracted position to the extended position is less than 5 degrees. 
     In an embodiment, the flow guide plate is configured to have a fixed position within the centrifugal compressor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of a heat transfer circuit of a HVACR system. 
         FIG.  2    is a side prospective view of an embodiment of a centrifugal compressor. 
         FIG.  3    is a front view of the centrifugal compressor in  FIG.  2   , according to an embodiment. 
         FIG.  4    is a cross-sectional view of the centrifugal compressor of  FIG.  2    as indicated in  FIG.  3   , according to an embodiment. 
         FIG.  5    is a front perspective view of an interstage throttle of the centrifugal compressor of  FIG.  2   , according to an embodiment. 
         FIG.  6    is rear perspective of a flow guide plate of the interstage throttle in  FIG.  5   , according to an embodiment. 
         FIG.  7    is a front view of the interstage throttle in  FIG.  5    with the flow guide plate omitted, according to an embodiment. 
         FIGS.  8  and  9    are each a rear perspective view of a throttle ring and an actuation mechanism of the interstage throttle in  FIG.  5   , according to an embodiment.  FIG.  8    shows the throttle ring in an extended position.  FIG.  9    shows the throttle ring in a reacted position. 
         FIGS.  10  and  11    are each a schematic diagrams illustrating the intermeshing of a throttle ring and the flow guide plate of the interstage throttle of  FIG.  6   , according to an embodiment.  FIG.  10    shows the throttle ring in a retracted position.  FIG.  11    shows the throttle ring in an extended position. 
         FIG.  12    is a side view of an embodiment of a throttle ring and a drive ring for an interstage throttle. 
         FIG.  13    is a block flow diagram for an embodiment of a method of operating a centrifugal compressor. 
     
    
    
     Like reference numbers represent like parts throughout. 
     DETAILED DESCRIPTION 
     A heating, ventilation, air conditioning, and refrigeration (“HVACR”) system can include a heat transfer circuit configured to heat or cool a process fluid (e.g., air, water and/or glycol, or the like). The heat transfer circuit includes a compressor that compresses a working fluid circulated through the heat transfer circuit. The compressor includes a first stage with a first impeller and a second stage with a second impeller. The first stage configured to compress the working fluid to a first pressure and the second stage configured to further compress the working fluid discharged from the first stage. An interstage throttle directs the working fluid from the first stage to the inlet of the second stage. 
     Embodiments described herein are directed to interstate throttles in centrifugal compressors, centrifugal compressors with an interstage throttle, HVACR systems that include centrifugal compressors, and methods of operating centrifugal compressors. 
       FIG.  1    is a schematic diagram of a heat transfer circuit  1  of a HVACR system, according to an embodiment. The heat transfer circuit  1  includes a compressor  10 , a condenser  20 , an expansion device  30 , and an evaporator  40 . In an embodiment, the heat transfer circuit  1  can be modified to include additional components. For example, the heat transfer circuit  1  in an embodiment can include an economizer heat exchanger, one or more flow control devices, a receiver tank, a dryer, a suction-liquid heat exchanger, or the like. 
     The components of the heat transfer circuit  1  are fluidly connected. The heat transfer circuit  1  can be configured as a cooling system (e.g., a fluid chiller of an HVACR, an air conditioning system, or the like) that can be operated in a cooling mode, and/or the heat transfer circuit  1  can be configured to operate as a heat pump system that can run in a cooling mode and a heating mode. 
     The heat transfer circuit  1  applies known principles of gas compression and heat transfer. The heat transfer circuit can be configured to heat or cool a process fluid (e.g., water, air, or the like). In an embodiment, the heat transfer circuit  1  may represent a chiller that cools a process fluid such as water or the like. In an embodiment, the heat transfer circuit  1  may represent an air conditioner and/or a heat pump that cools and/or heats a process fluid such as air, water, or the like. 
     During the operation of the heat transfer circuit  1 , a working fluid (e.g., refrigerant, refrigerant mixture, or the like) flows into the compressor  10  from the evaporator  40  in a gaseous state at a relatively lower pressure. The compressor  10  compresses the gas into a high pressure state, which also heats the gas. After being compressed, the relatively higher pressure and higher temperature gas flows from the compressor  10  to the condenser  20 . In addition to the working fluid flowing through the condenser  20 , a first process fluid PF 1  (e.g., external air, external water, chiller water, or the like) also separately flows through the condenser  20 . The first process fluid absorbs heat from the working fluid as the first process fluid PF 1  flows through the condenser  20 , which cools the working fluid as it flows through the condenser. The working fluid condenses to liquid and then flows into the expansion device  30 . The expansion device  30  allows the working fluid to expand, which converts the working fluid to a mixed vapor and liquid state. An “expansion device” as described herein may also be referred to as an expander. In an embodiment, the expander may be an expansion valve, expansion plate, expansion vessel, orifice, or the like, or other such types of expansion mechanisms. It should be appreciated that the expander may be any type of expander used in the field for expanding a working fluid to cause the working fluid to decrease in temperature. The relatively lower temperature, vapor/liquid working fluid then flows into the evaporator  40 . A second process fluid PF 2  (e.g., air, water, or the like) also flows through the evaporator  40 . The working fluid absorbs heat from the second process fluid PF 2  as it flows through the evaporator  40 , which cools the second process fluid PF 2  as it flows through the evaporator  40 . As the working fluid absorbs heat, the working fluid evaporates to vapor. The working fluid then returns to the compressor  10  from the evaporator  40 . The above-described process continues while the heat transfer circuit  1  is operated, for example, in a cooling mode. 
       FIG.  2    is a side perspective view of an embodiment of a centrifugal compressor  100 . In an embodiment, the centrifugal compressor  100  is the compressor  10  in the heat transfer circuit  1  in  FIG.  1   . The compressor  100  includes a housing  102  having a suction inlet  104  and a discharge outlet  106 . Working fluid enters the housing  100  through the suction inlet  104 , is compressed by the compressor  100 , and is discharged as compressed working fluid from the discharge outlet  106 . The compressor  100  includes a first stage S 1 , a second stage S 2 , and an interstage throttle  130 . The working fluid is compressed in the first stage S 1  (e.g., to a first pressure P 1 ), flows from the first stage to the second stage S 2 , and is then further compressed to a higher pressure (e.g., second pressure P 2 ) in the second stage S 1 . The compressed working fluid discharged from the first stage S 1  flows from the first stage S 1  to the second stage S 2  through the interstage throttle  130 . The interstage throttle  130  is configured to control a flowrate of the working fluid from the first stage S 1  to the second stage S 2 . 
       FIG.  3    is a front view of the centrifugal compressor  100 .  FIG.  4    is a cross-sectional view of the centrifugal compressor  100  as indicated in  FIG.  3   . As shown in  FIG.  4   , the compressor  100  includes the first stage S 1 , the second stage S 2 , and the interstage throttle  130  that connects the first stage S 1  to the second stage S 2 . The first stage S 1  and the second stage S 2  each include an impeller  110 A,  110 B that rotates to compress the working fluid within their respective stage S 1 , S 2 . 
     The compressor  100  also includes a driveshaft  112 , a rotor  114 , and a stator  116 . The impellers  110 A,  110 B are each affixed to the driveshaft  112 . For example, the first impeller  110 A is affixed to an end of the driveshaft  112  while the second impeller  110 B is affixed closer to a middle of the shaft  112 . The rotor  114  is attached to the driveshaft  112  and is rotated by the stator  116 , which rotates driveshaft  112  and the impellers  110 A,  110 B. The rotor  114  and stator  116  form an electric motor of the compressor  110 . The electric motor (e.g., the stator  116  and the rotor  114 ) operates according to generally known principles. In another embodiment, the driveshaft  112  may be connected to and rotated by an external electric motor, an internal combustion engine (e.g., a diesel engine or a gasoline engine), or the like. It is appreciated that in such embodiments that the rotor  114  and the stator  116  would not be present within the housing  102  of the compressor  100 . The driveshaft  112  extends through the first and second stages S 1  and S 2  as well as the interstage throttle  130  as shown in  FIG.  4   . It should be appreciated that the terms “axial”, “radial”, and “circumferential” as used herein are generally respect to the axis of the compressor  100  (e.g., the axis of the driveshaft  112 ), unless specified otherwise. 
     The flow path F 1  of working fluid through the compressor  100  is indicated in dashed arrows in  FIG.  4   . The flow path F 1  extends from the suction inlet  104  to the discharge outlet  106  of the compressor  100 . The working fluid enters the compressor  100  through the suction inlet  104 , is compressed within the first stage S 1  by the first impeller  110 A, flows through the interstage throttle  130  to the second stage S 2 , is further compressed in the second stage S 2  by the second impeller  110 B, and is then discharged from the compressor  100  through the discharge  106 . The first impeller  110 A in the first stage S 1  is configured to compress the working fluid from an inlet pressure (e.g., pressure P 1 ) to a first pressure P 1 , and the second impeller  110 B in the second stage S 2  is configured to further compress the working fluid to a second pressure P 2  that is greater than the first pressure P 1 . 
     In flow path F 1 , the interstage throttle  130  is disposed between the first impeller  110 A of the first stage S 1  and the second impeller  110 B of the second stage S 2 . The interstage throttle  130  is disposed between the outlet  118  of the first impeller S 1  and the inlet  120  of the second impeller  110 A. The driveshaft  112  extends through the interstage throttle  130 . The interstage throttle  130  fluidly connects the outlet  118  of the first impeller  110 A to the inlet  120  of the second impeller  110 B. The interstage throttle  130  directs the working fluid discharged from the first stage S 1  (e.g., the compressed working fluid at the first pressure P 1 ) to the second impeller  110 B of the second stage S 2 . For example, the interstage throttle  130  directs the compressed working fluid (after being discharged radially outward from the first impeller  110 A) radially inward to the inlet  120  of the second impeller  110 B. The interstage throttle  130  is adjustable to control the flowrate of the compressed working fluid flowing from the first stage S 1  to the second stage S 2 . The interstage throttle  130  includes an actuator  170  for operating the interstage throttle  130 . The actuator  170  is operable/actuates to adjust the flowrate of the compressed working fluid flowing through the interstage throttle  130 . For example, a controller (not shown) of the compressor  100  and/or the HVACR controller may be configured to control the capacity of the compressor  100  by controlling the position/actuation of the actuator  170 . 
     The interstage throttle  130  includes guide vanes  144  and channels  146  formed by the guide vanes  144 . The channels  146  spiral radially inward and are shown in more detail in  FIGS.  5  and  6   . As shown in  FIG.  4   , the working fluid flows through interstage throttle  130  by flowing through the channels  146 . The channels  146  direct the working fluid discharged from the first stage S 1  radially inward to the inlet  120  of the second impeller  110 B. The interstage throttle  130  includes a throttle ring  160  configured to be actuated to adjust a size of the channels  146  (e.g., a cross-sectional area of the channels  146 ). 
     The throttle ring  160  includes teeth  162  that extend towards the flow guide plate  140 . The throttle ring  160  is configured to be actuated in the axial direction (e.g., in direction D 1 , in direction D 2 ) relative to the channels  146 . The axial movement of the throttle ring  160  changes the length of the teeth  162  disposed in the channels  146  to adjust the cross-sectional area of the channels  146 . For example, when the throttle ring  160  is actuated towards the channels  146  (e.g., in a positive axial direction D 1 ), the teeth  162  extend further into the channels  146  and reduce the cross-sectional area of the channels  146 . As each tooth  162  is disposed further into its respective channel  146 , the tooth  162  partially blocks more of the channel  146  and decreases the cross-sectional area of the channel  146  (e.g., decreases the open cross-sectional area in each channel). The decreased cross-sectional area of the channels  146  decreases the flowrate of the working fluid through the channels  146  and the interstage throttle  130 . When the throttle ring  160  is actuated away from the channels  146  (e.g., in the negative axial direction D 2 ), the teeth  162  extend less into the channels  146  and the cross-sectional area of the channels  146  is increased, which increases the flow of the working fluid through the interstage throttle  130 . For example, the throttle ring  160  in an embodiment may have a retracted position in which the teeth  162  disposed entirely outside of the channels  146 . The configuration of the interstage throttle  130  is discussed in more detail below. 
       FIG.  5    is a front perspective view of the interstage throttle  130  of the compressor  100 . The interstage throttle  130  includes a housing  132 , a flow guide plate  140 , the actuator  170 , and an actuation linkage assembly  172 . The housing  132  is part of the housing  102  of the compressor  100 . The housing  132  remains stationary during operation of the compressor  100  (e.g., remains stationary during rotation of the driveshaft  112 ). 
     The actuation linkage assembly  172  connects to the actuator  170  and extends through the housing  132 . The actuator  170  actuates the actuation linkage assembly  172  to actuate/move the throttle ring  160  within the housing  132 . For example, the actuation linkage assembly  172  includes a shaft  174  that extends through the housing  132 . The actuator  170  actuates (e.g., extends, retracts) to rotate the shaft  174 . As shown in  FIG.  5   , the actuator  170  can be mounted external to the housing  132 . Actuation of the throttle ring  160  is discussed in more detail below. 
     The flow guide plate  140  includes a baseplate  142  and the guide vanes  144  that extend along the baseplate  142 . The guide vanes  144  are provided on the baseplate  142 . The flow guide plate  140  includes through-hole  149  for the driveshaft  112  (shown in  FIG.  2   ). The axis A of the driveshaft  112 /flow guide plate  140  is indicated in  FIG.  5   . During operation of the compressor  100 , the flow guide plate  140  remains in a fixed positon relative to the housing  132  (e.g., does not rotate with the driveshaft  112 ). The working fluid flows through the interstage throttle  130  by flowing through the channels  146  of the flow guide plate  140 . The channels  146  direct the working fluid radially inward towards a center of the flow guide plate  140  (e.g., towards the axis A of the driveshaft  112 /compressor  100 ). The working fluid from the first stage S 1  enters the channels  146  along the outer edge  148  of the baseplate  142  then flows radially inward through the channels  146 . 
       FIG.  6    is rear perspective of the flow guide plate  140  of the interstage throttle  130 . The rear  141  of the flow guide plate  140  shown in  FIG.  6    faces the interstage throttle ring  130  and the second impeller  110 B of the second stage S 2 . The channels  146  are formed between the guide vanes  144 . A respective channel  146  is formed between each adjacent pair of the guide vanes  144 . The guide vanes  144  and the channels  146  each extend radially inward (e.g., in direction D 4 , in direction D 5 , etc.). The guide vanes  144  and the channels  146  each have a spiral shape as shown in  FIG.  6   . The guide vanes  144  and channels  146  extending both radially inward and circumferentially along the baseplate  142 . The flow direction for working fluid through the channels  146  is indicated in dashed lines in  FIG.  6   . The teeth  162  of the throttle ring  160  (shown in  FIGS.  5  and  8 - 11   ) are configured to fit into the channels  146 . For example, each tooth  162  is configured to fit into a respective channel  146  between a respective pair of the guide vanes  144 . The tooth  162  has a circumferential thickness that is less than the circumferential distance between its respective pair of guide vanes  144  (e.g., the thickness of its respective channel  146  in the circumferential direction D 3 ). The throttle ring  160  is configured to be actuatable in the axial direction to move each tooth  162  in the axial direction (e.g., direction D 1  and direction D 2  in  FIG.  2   ) into its respective channel  146 . 
       FIG.  7    is a rear perspective view of the interstage throttle  130  with the flow guide plate  140  omitted.  FIGS.  8  and  9    show a rear perspective view of the throttle ring  160  and the actuation mechanism  99  of the interstage throttle  130  for actuating the throttle ring  160 .  FIG.  8    shows the throttle ring  160  when in its extended position.  FIG.  9    shows the throttle ring  160  in its retracted position. 
     The actuation mechanism  99  for the throttle ring  130  includes the actuation linkage assembly  172 , a drive ring  180 , drive linkages  182 , and support linkages  184 . In the illustrated embodiment, the actuation linkage assembly  172  includes the shaft  174  and is configured to utilize the motion of the actuator  170  (e.g., linear motion, extension, retraction, etc.) to rotate the drive ring  180 . For example, the linear extension of actuator  170  rotates the shaft  172  of the actuation linkage assembly  170  and the rotation of the shaft  172  in turn rotates the drive ring  180 . As shown in  FIGS.  8  and  9   , the drive ring  180  may have at or about the same circumference as the throttle ring  160 . The drive ring  180  is obscured by the throttle ring  160  in  FIG.  7   . In an embodiment, the circumference of the drive ring  180  and of the throttle ring  160  are less than 10% different. In another embodiment, the circumferences of the drive ring  180  and the throttle ring  160  may be less than 5% different). 
     The linkages  182 ,  184  are configured to move the throttle ring  160  in the axial direction (e.g., positive axial direction D 1 , negative axial direction D 2 ) using the rotation of the drive ring  180 . The drive linkages  182  connect the drive ring  180  to the throttle ring  160 . Each of the drive linkages  182  separately extends from the drive ring  180  to the throttle ring  160 . As shown in  FIG.  8   , the throttle ring  160  and the drive ring  180  includes radial shafts  164 ,  181  (e.g., pins, bolts, integral shafts, or the like) that extend radially outward from the throttle ring  160  and the drive ring  180 , respectively. It should be appreciated that one or more of the radial shafts  164 ,  181  may extend radially inward in another embodiment. The linkages  182 ,  184  are rotatably connected to the radial shafts  164 ,  181  on the rings  160 ,  180 . As shown in the  FIGS.  8  and  9   , the linkages  182 ,  184  can each be an arm that connects their respective structures. The linkages  182 ,  184  are configured to use the rotation of the drive ring  180  to move the throttle ring  160  in the axial direction with little to no rotation of the throttle ring  160 . 
     As shown in  FIG.  8   , each drive linkage  182  has a first end  183 B that is rotatably connected to the throttle ring  160  and a second end  183 A that is rotatably attached to the drive ring  180 . For example, each drive linkage  182  has a through-hole on its first end  183 B that is inserted onto a respective radial shaft  164  on the throttle ring  160 . For example, each drive linkage  182  has a through-hole on its second end  183 A that is inserted onto a respective radial shaft  181  on the drive ring  180 . 
     As shown in  FIG.  7   , each support linkage  184  has a first end  185 A that is rotatably connected to the throttle ring  160  and a second end  185 B that is rotatably connected to the housing  132 . For example, each support linkage  184  has a through-hole on its first end  185 A that is inserted onto a respective radial shaft  164  on the throttle ring  160 . For example, each support linkage  184  has a through-hole on its second end  185 B that is inserted onto a respective shaft  134  on the housing  132 . For example, the shaft  134  on the housing  132  extends in the axial direction (e.g., in direction D 3  in  FIG.  2   ). 
     As shown in  FIG.  7   , the drive linkages  182  and support linkages  184  are provided in pairs. In each drive linkage  182  and the support linkage  184  pair, the drive linkage  182  and the support linkage  184  connect to the throttle ring  160  at the same location. For example, the drive linkage  182  and the support linkage  184  in each pair is rotatably connect to the same radial shaft  164  of the throttle ring  160 . The drive linkage  182  is configured to transfer the movement from the drive ring  180  (e.g., rotation of the drive ring  180 ) to the shaft  164  of the throttle ring  160  while the support linkage  184  is configured to limit/prevent rotation of the throttle ring  160 . In the illustrated embodiment, the interstage throttle  130  includes four pairs of the drive and supports linkages  182 ,  184 . However, it should be appreciated that the interstage throttle  130  in an embodiment may include a different number of the linkages  182 ,  184 . For example, the interstage throttle  130  in an embodiment may include three or more pairs of the linkages  182 ,  184 . 
     As shown in  FIGS.  8  and  9   , the linkages  182 ,  184  are configured so that the rotation of the drive ring  180  moves the throttle ring  160  in the axial direction with limited rotational movement. For example, the throttle ring  160  is configured to rotate less than 5 degrees between its fully retracted position to fully extend position. In an embodiment, the throttle ring  160  may be configured to rotate less than 3 degrees between its from its fully retracted position to its fully extend position. For example, the throttle ring  160  moves from its fully retracted position to its fully extended position when the actuator  170  is actuated moves from 0% extended to 100% extended, or from 100% extended to 0% extended. 
     As shown in  FIG.  8   , the teeth  162  of the throttle ring  160  are spaced apart from each other in the circumferential direction D 3 . A respective gap  163  is formed between each circumferentially adjacent pair of teeth  162 . Each gap is configured to accept a respective one of the guide vanes  144  (omitted in  FIG.  8   ) when the throttle ring  160  is in its extended position (e.g., see  FIG.  11   ). 
       FIGS.  10  and  11    are schematics diagrams illustrating the intermeshing of the throttle ring  160  and the flow guide plate  140 . For example, the view in  FIGS.  10  and  11    are a partial cross-section of throttle ring  160  and flow guide plate  140  in the axial direction.  FIG.  10    shows the throttle ring  160  in the retracted position (e.g., as shown in  FIG.  9   ).  FIG.  11    shows the throttle ring  160  in the extended position (e.g., shown in  FIG.  8   ). The flow direction of the working fluid through the channels  146  would be into the page in  FIGS.  10  and  11   . For example, radially inward is into the page in  FIGS.  10  and  11   . 
     As shown in  FIG.  10   , the teeth  162  of the throttle ring  160  are spaced apart from each other in the circumferential direction D 3 . The guide vanes  144  are space apart from each other in the circumferential direction D 3  such that the channels  146  are spaced apart from each other in the circumferential direction D 3 . Each of the teeth  162  has a width W 1  in the circumferential direction that is smaller than the width W 2  of its respective channel  146  such that the teeth  162  fit into their respective channels  146 . A gap is formed between adjacent pair of teeth  162   
     As shown in  FIG.  10   , each of the channels  146  has a cross sectional area A 1  when the throttle ring  160  is in its retracted position. The working fluid flows through the channels  146  by passing through the cross-sectional area A 1  between the flow guide plate  140  and the tips  164  of the teeth  162 . In the illustrated embodiment, the teeth  162  of the throttle ring  160  are not disposed in the channels  146  when the throttle ring  160  is in its retracted position. However, it should be appreciated that the throttle ring  160  in an embodiment may be configured such that the throttle ring  160  is not fully removed from the channels  146  when in its retracted position (e.g., part of the teeth  162  can remain disposed in the channels  146  when in the retracted position). 
     When actuated into the extended position as shown in  FIG.  11   , the throttle ring  160  moves closer to the flow guide plate  140  in the axial direction D 1  and the teeth  162  are disposed in the channels  146 . The movement of the throttle ring  160  disposes a greater length Li of the teeth  162  in the channels  146  and moves the teeth  162  closer to the baseplate  142  of the flow guide plate  140 . The teeth  162  and channels  146  intermesh together in the extended position. Each tooth  162  is disposed in its respective channel  146  and between a respective adjacent pair (e.g., adjacent in the circumferential direction D 3 ) of the guide vanes  144 . 
     When moved to the extended position, the teeth  162  partially block the channels  146  and reduce the open height H of the channels. The blocking of the channels  146  reduces their open cross sectional area A 2  at the teeth  162 . This creates a pressure drop for the working fluid to flow through the smaller cross sectional area A 2  which reduces the flow rate of the working fluid through the channels  146  (e.g., the flow rate of the working fluid through the interstage throttle  130 ). 
       FIG.  12    is a side view of another embodiment of a drive linkage  282  for connecting a drive ring  280  to a throttle ring  260  in an interstage throttle  230 . For example, the interstage throttle  230  may have features similar to the interstage throttle in  FIG.  5    except as described below. The throttle ring  260  is actuated by rotating the drive ring  280 . For example, the rotational axis of the drive ring  280  would extend vertically in  FIG.  12    such that rotation of the drive ring  280  in the circumferential direction D 3  would cause left side of the drive ring  280  to move into the page and the right side of the drive ring  280  to move out of the page. For example, an actuator and actuation linkage assembly similar to the actuator  170  and actuation linkage assembly  172  as described above can be used to drive the drive ring  280  to rotate. The rotation of the drive ring  280  causes the throttle ring  260  to move in the axial direction (e.g., positive axial direction D 1 ).  FIG.  12    shows the throttle ring  260  in its extended position. The throttle ring  260  is moved in the axial direction (e.g., opposite to the positive axial direction D 1 ) by rotating the drive ring  280  in the opposite direction (e.g., opposite to the circumferential direction D 3 ). 
     In the illustrated embodiment, the drive linkage  282  is a slot in the drive ring  280 . A radial shaft  264  of the throttle ring  260  extends through the slot. The slot is angled between the axial direction D 1  and circumferential direction D 3  such that the rotation of drive ring  280  forces the radial shaft  264  to move axially within the slot which moves the throttle ring  260  in the axial direction D 1 . In  FIG.  12   , the drive ring  280  has been rotated in a first direction (e.g., circumferential direction D 3 ) to move the radial shaft  264  to the end of the slot closest to the throttle ring  260  (e.g., to move the throttle ring  260  to its extended position). The drive ring  280  is then rotated in the opposite direction (e.g., opposite to the circumferential direction D 3  in  FIG.  12   ) moving the radial shaft  264  in the opposite direction until reaching the end of the slot farthest from the throttle ring  260  (e.g., moving the throttle ring  260  to its retracted position). A respective drive linkage  282  (e.g., a respective slot in the drive ring  280 ) can be provided for each radial shaft  264  of the throttle ring  260  as similarly discussed for the drive linkages in  FIGS.  7 - 9   . In an embodiment, support linkages (e.g., support linkages  184 ) provided for throttle ring  260  similar to the throttle ring  160  in  FIGS.  7 - 10    such that the rotation of the throttle ring  260  when actuated in the axial direction is limited. For example, a support linkage is provided for the radial shaft  264  that limits/prevents the radial shaft  264  in the circumferential direction D 3  while allowing the radial shaft  264  to move axially within the slot when the drive ring  280  is rotated. 
       FIG.  13    is a block diagram of a method  1000  of operating a centrifugal compressor. In an embodiment, the method  1000  may be applied to the centrifugal compressor  100  of  FIG.  1   . The method starts at  1010 . 
     At  1010 , working fluid is compressed in and discharged from a first stage (e.g., first stage S 1 ) of the compressor. Compressing the working fluid in the first stage  1010  may include rotating a first impeller (e.g., first impeller  110 A) of the first stage  1012 . The rotating of the first impeller at  1012  compresses the working fluid from an inlet pressure to a higher pressure (e.g., first pressure) and radially discharges the compressed working fluid from the first impeller  110 A at the first pressure  1012 . The method  1010  then proceeds from 1010 to 1020. 
     At  1020 , the compressed working fluid is directed from the first stage to a second stage of the compressor (e.g., second stage S 2 ) via channels (e.g., channels  146 ) in an interstage throttle (e.g., interstage throttle  130 ). The compressed working fluid flowing from the first stage to the second stage through the channels in the interstage throttle. Directing the compressed working fluid at  1020  includes actuating the interstage throttle  1022  to control the flow (e.g., flowrate) of the working fluid to the second stage. Actuating the interstage throttle at  1022  includes axially moving a throttle ring of the interstage throttle (e.g., throttle ring  160 ,  260 )  1024 . Actuating the throttle ring at  1024  includes rotating a drive ring (e.g., drive ring  180 ) connected to the throttle ring. The rotation of the drive ring moving the throttle ring in an axial direction closer to the channels. For example, the movement of the throttle ring in the axial direction closer to the channels reduces the cross-sectional areas (e.g., area A 1 , area A 2 ) of the channels and reduces the flowrate of the working fluid through the interstage throttle  130 . The compressor (e.g., a controller of the compressor) is configured to adjust the position of the interstage throttle  130  to control the capacity of the compressor (e.g., the volumetric discharge from the compressor) to match a desired capacity based on the cooling or heating to be provided by the HVACR system (e.g., heating or cooling to be provided by the heat transfer circuit  1 ). 
     It should be appreciated that the method  1000  in an embodiment may be modified to have features as discussed above for the compressor  10  in  FIG.  1   , the compressor  100  in  FIGS.  2 - 4   , the interstage throttle  130  in  FIGS.  5 - 11   , and/or the interstage throttle  230  in  FIG.  12   . 
     Aspects: 
     Any of Aspects 1-9 can be combined with any of Aspects 10-20 and any of aspects 10-12 can be combined with Aspects 13-20. 
     Aspect 1. An interstage throttle for a centrifugal compressor including a first stage and a second stage, the interstage throttle comprising: a flow guide plate including a plurality of guide vanes forming channels extending radially inward, the channels configured to direct working fluid discharged from the first stage to an inlet of the second stage; a throttle ring including teeth; a drive ring; linkage assemblies connecting the drive ring to the throttle ring such that rotation of drive ring moves the throttle ring in an axial direction relative to the flow guide plate between a retracted position and an extended position, wherein in the extended position, the teeth of the throttle ring are disposed in and partially block the channels.
 
Aspect 2. The interstage throttle of Aspect 1, wherein the teeth of the throttle ring block less of the channels in the retracted position than in the extended position.
 
Aspect 3. The interstage throttle of any one of Aspects 1 and 2, wherein the throttle ring includes radial shafts, each of the linkage assemblies include pairs of a drive linkage and a support linkage connected to the radial shafts of the throttle ring, the drive linkage and the support linkage in each of the pairs connected to the same respective one of the radial shafts on the throttle ring.
 
Aspect 4. The interstage throttle ring any one of Aspect 3, further comprising: a housing, the flow guide plate, the throttle ring, and the drive ring disposed within the housing, wherein the drive linkages connect the drive ring to the throttle ring, the drive linkages configured to transfer rotation of the drive ring into axial movement of the throttle ring, and the support linkages connect the throttle ring to the housing, the support linkages configured to prevent rotation of the throttle ring.
 
Aspect 5. The interstage throttle ring of any one of Aspects 3 and 4, wherein in each of the pairs of the drive linkage and the support linkage: the drive linkage has a first end rotatably connected to the respective radial shaft on the throttle ring and a second end rotatably connected to a respective radial shaft on the drive ring.
 
Aspect 6. The interstage throttle ring of any one of Aspects 3-5, wherein in each of the pairs of the drive linkage and the support linkage: the support linkage has a first end connected to the respective radial shaft on the throttle ring and a second end connected to a housing of the interstage throttle.
 
Aspect 7. The interstage throttle of any one of Aspects 1-6, further comprising: an actuator and an actuation linkage assembly connecting the actuator to the drive ring, actuation of the actuator extends the actuator causes rotation of the drive ring, and retraction of the actuator causes opposite rotation of the drive ring.
 
Aspect 8. The interstage throttle of any one of Aspects 1-7, wherein rotation of the throttle ring from the retracted position to the extended position is less than 5 degrees.
 
Aspect 9. The interstage throttle of any one of Aspects 1-8, wherein the flow guide plate is configured to have a fixed position in the interstage throttle.
 
Aspect 10. A method of operating a centrifugal compressor, comprising: compressing a working fluid to a first pressure in the first stage; directing the working fluid discharged from the first stage to a second stage via channels in a interstage throttle, the interstage throttle including a flow guide plate including a plurality of guide vanes forming the channels extending radially inward, a throttle ring, a drive ring, and linkage assemblies connecting the drive ring to the throttle ring, wherein the directing of the working fluid via the channels includes: rotating the drive ring to move the throttle ring in an axial direction relative to the flow guide plate between a retracted position and an extended position, the rotation of the drive ring moving the throttle ring between in the axial direction between the retracted position and the extended position, the throttle ring in the extended position having teeth disposed in and partially blocking the channels.
 
Aspect 11. The method of Aspect 10, further comprising: further compressing the working fluid in the second stage from the first pressure to a second pressure.
 
Aspect 12. The method of any one of Aspects 10 and 11, wherein the rotating of the drive ring includes extending or retracting an actuator connected to the drive ring, the extending or retracting of the actuator causing rotation of the drive ring.
 
Aspect 13. A centrifugal compressor, comprising: a first stage including a first impeller configured to compress working fluid to a first pressure; a second stage including a second impeller configured to compress the working fluid to a second pressure; an interstage throttle fluidly connecting the first stage to the second stage, the interstage throttle including: a flow guide plate including a plurality of guide vanes forming channels extending radially inward, the channels configured to direct the working fluid discharged from the first stage at the first pressure to an inlet of the second stage, a throttle ring including teeth, a drive ring, and linkage assemblies connecting the drive ring to the throttle ring such that rotation of the drive ring moves the throttle ring in an axial direction relative to the flow guide plate between a retracted position and an extended position, wherein in the extended position, the teeth of the throttle ring are disposed in and partially block the channels.
 
Aspect 14. The centrifugal compressor of Aspect 13, wherein the teeth of the throttle ring block less of the channels in the retracted position than in the extended position.
 
Aspect 15. The centrifugal compressor of any one of Aspects 13 and 14, wherein the throttle ring includes radial shafts, each of the linkage assemblies include pairs of a drive linkage and a support linkage connected to the radial shafts of the throttle ring, the drive linkage and the support linkage in each of the pairs connected to the same respective one of the radial shafts on the throttle ring.
 
Aspect 16. The centrifugal compressor of Aspect 15, further comprising: a housing, the flow guide plate, the throttle ring, and the drive ring disposed within the housing, wherein the drive linkages connect the drive ring to the throttle ring, the drive linkages configured to transfer rotation of the drive ring into axial movement of the throttle ring, and the support linkages connect the throttle ring to the housing, the support linkages configured to prevent rotation of the throttle ring.
 
Aspect 17. The centrifugal compressor of any one of Aspects 13-16, further comprising: an actuator and an actuation linkage assembly connecting the actuator to the drive ring, actuation of the actuator extends the actuator causing rotation of the drive ring, and retraction of the actuator causes opposite rotation of the drive ring.
 
Aspect 18. The centrifugal compressor of Aspect 17, further comprising: a housing, wherein the flow guide plate, the throttle ring, and the drive ring are disposed within the housing, the actuator is external to the housing, and the actuation linkage assembly extends through the housing.
 
Aspect 19. The centrifugal compressor of any one of Aspects 13-18, wherein rotation of the throttle ring from the retracted position to the extended position is less than 5 degrees.
 
Aspect 20. The centrifugal compressor of any one of Aspects 13-19, wherein the flow guide plate is configured to have a fixed position within the centrifugal compressor.
 
     The terminology used herein is intended to describe particular embodiments and is not intended to be limiting. The terms “a,” “an,” and “the” include the plural forms as well, unless clearly indicated otherwise. The terms “comprises” and/or “comprising,” when used in this Specification, specify the presence of the 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, elements, and/or components. In an embodiment, “connected” and “connecting” as described herein can refer to being “directly connected” and “directly connecting”. 
     With regard to the preceding description, it is to be understood that changes may be made in detail, especially in matters of the construction materials employed and the shape, size, and arrangement of parts without departing from the scope of the present disclosure. This Specification and the embodiments described are exemplary only, with the true scope and spirit of the disclosure being indicated by the claims that follow.