Variable geometry diffuser mechanism

A system for a variable capacity centrifugal compressor for compressing a fluid, the compressor having a housing and an impeller, the impeller being rotatably mounted in the housing, the system comprising:

• a nozzle base plate fixed to the housing adjacent the impeller, the nozzle base plate having an elongated surface that cooperates with an opposed interior surface on the housing to define a diffuser gap, the elongated surface of the nozzle base plate having a groove adjacent the diffuser gap;
• three support blocks positioned concentrically on a back side of the nozzle base plate opposite the diffuser gap about 120° apart;
• a drive ring mounted substantially out of contact with the support blocks rotationally selectably movable with respect to the support blocks and the nozzle base plate between a first position and a second position, the drive ring a top surface, a bottom surface, an inner circumference extending between the top surface and the bottom surface, an outer circumference extending between the top surface and the bottom surface, the inner circumference including an inner circumferential groove, the drive ring including three cam tracks positioned on the outer circumference of the drive ring about 120° apart, each of the cam tracks aligned with each of the support blocks;
• an actuator having a motor movable between a first axial position and a second axial position attached to the drive ring to rotate the drive ring from the first position to the second position;
• three drive pins, one drive pin extending through each of the support blocks and the nozzle base plate, a first end of each drive pin including a cam follower mounted into one of the cam tracks on drive ring and the second end of each drive pin extending through the nozzle base plate into the groove on the surface of the nozzle base plate;
• three axial bearing assemblies, one axial bearing assembly mounted to each of the support blocks and each axial bearing assembly positioned within the inner circumferential groove of the drive ring to resist axial movement of the drive ring as it rotates;
• three radial bearing assemblies, one radial bearing assembly mounted to each of the support blocks and each radial bearing assembly positioned in contact with an inner circumferential surface to resist radial movement of the drive ring as it rotates;
• a diffuser ring mounted on the second end of the drive pins extending into the groove on the nozzle base plate;
• a sensor positioned within the compressor to provide signals indicative of a fluid condition in the compressor;
• a controller in communication with the sensor and the actuator, the controller sending a signal to the actuator to position the drive ring and connected diffuser ring in response to signals received from the sensor;
• wherein the motion of the actuator in response to the signal from the controller causes the rotational movement of the drive ring between a first position and a second position, causing axial movement of the drive pins by movement of the cam followers in the cam tracks, which causes movement of diffuser ring between a first position corresponding to a first position of the drive ring and a second position corresponding to a second position of the drive ring to control fluid flow through the diffuser gap and prevent compressor stall.

A centrifugal compressor, comprising:

• a housing;
• a fluid inlet;
• an impeller assembly rotatably mounted on a shaft in the housing for compressing fluid introduced through the inlet;
• a fluid outlet to discharge compressed fluid from the impeller;
• a nozzle base plate connected to the housing adjacent the impeller, the nozzle base plate having an elongated surface that cooperates with an opposed interior surface on the housing to define a diffuser gap;
• a plurality of support blocks positioned on a back side of the nozzle base plate opposite the diffuser gap;
• a drive ring rotatably mounted to the support blocks and movable between a first position and a second position, the drive ring including a plurality of cam tracks positioned on a circumference of the drive ring, at least two of the plurality of cam tracks aligned with at least two of the plurality of support blocks;
• an actuating means movable in its axial direction attached to the drive ring and movable between a first axial position and a second axial position to move the drive ring between the first position and the second position;
• a plurality of drive pins, each drive pin extending through a corresponding support block and the nozzle base plate, each drive pin having a first end and a second end opposite the first end, the first end of the drive pin including a cam follower mounted into one of the plurality of cam tracks on the drive ring and the second end of the drive pin extending through the nozzle base plate and protruding from the elongated surface;
• a diffuser ring mounted on the second end of each of the plurality of drive pins protruding from the nozzle base plate surface;
• wherein the rotational movement of the drive ring between a first position and a second position moves the cam followers in the cam track which axially moves the drive pins, the axial movement of the drive pins moves the diffuser ring between a retracted position in which the diffuser ring is distal from the opposed interior surface of the housing to increase fluid flow through the diffuser gap and an extended position in which the diffuser ring is proximal to the opposed interior surface of the housing to substantially close the diffuser gap and reduce fluid flow through the diffuser gap.