Centrifugal compressor having variable geometry diffuser and method thereof

Abstract

A centrifugal compressor is provided. The centrifugal compressor includes a plurality of diffuser vanes arranged in a circumferentially spaced array about a machine axis. Each diffuser vane is mounted on a respective shaft. Each of the shafts is coupled to a ring that is rotatable about the machine axis. A worm drive is provided that includes a worm that meshes with a worm gear or a segment of a worm gear mounted along a portion of the circumference of the ring. A step motor is coupled to the worm. The step motor is operable to rotate the worm about a worm axis perpendicular to the machine axis, such that the worm drive transmits rotational torque from the step motor to the ring, to resultantly vary the position of the diffuser vanes.

1 . A centrifugal compressor, comprising:
 a plurality of diffuser vanes arranged in a circumferentially spaced array about a machine axis, each diffuser vane being mounted on a respective shaft;   a ring to which each of the shafts is coupled to, the ring being rotatable about the machine axis;   a worm drive including a worm that meshes with a won't gear or a segment of a worm gear mounted along at least a portion of the circumference of the ring; and   a step motor coupled to the worm and operable to rotate the worm about a worm axis perpendicular to the machine axis, such that the worm drive transmits rotational torque from the step motor to the ring, to resultantly vary the position of the diffuser vanes.   
     
     
         2 . The centrifugal compressor according to  claim 1 , wherein each shaft is coupled to the ring by a radial arm that transmits rotational torque from the ring to the respective shaft, and resultantly, to the respective diffuser vane mounted thereon. 
     
     
         3 . The centrifugal compressor according to  claim 2 , wherein a plurality of bearings are provided along the circumference of the ring, wherein each radial arm is flexibly coupled to a respective bearing by means of a slot provided on the respective arm. 
     
     
         4 . The centrifugal compressor according to  claim 1 , wherein the step motor is coupled to the worm by means of a flexible coupling. 
     
     
         5 . The centrifugal compressor according to  claim 1 , further comprising a volute casing, wherein the ring is axially and radially supported on the volute casing by means a plurality of bearing assemblies disposed circumferentially around the volute casing. 
     
     
         6 . A method for providing variable geometry of diffuser vanes of a centrifugal compressor, comprising:
 mounting each of a plurality of diffuser vanes on a respective shaft, such that the diffuser vanes are arranged in a circumferentially spaced array about a machine axis;   coupling each of the shafts to a ring that is rotatable about the machine axis;   disposing a worm drive including a worm that meshes with a worm gear or a segment of a worm gear mounted along a portion of the circumference of the ring; and   coupling a step motor to the worm, the step motor being operable motor to rotate the worm about a worm axis perpendicular to the machine axis, such that the worm drive transmits rotational torque from the step motor to the ring, to resultantly vary the position of the diffuser vanes.   
     
     
         7 . The method according to  claim 6 , further comprising coupling each shaft to the ring by a radial arm that transmits rotational torque from the ring to the respective shaft, and resultantly, to the respective diffuser vane mounted thereon. 
     
     
         8 . The method according to  claim 7 , further comprising:
 disposing a plurality of bearings along the circumference of the ring, and   flexibly coupling each radial arm to a respective bearing by means of a slot provided on the respective arm.   
     
     
         9 . The method according to  claim 6 , further comprising coupling the step motor to the worm by means of a flexible coupling. 
     
     
         10 . The method according to  claim 6 , further comprising disposing a plurality of bearing assemblies circumferentially around a volute casing of the compressor, and axially and radially supporting the ring on the volute casing by means of the plurality of bearings.