Gas compressor and method for controlling flow rate thereof

Abstract

Provided is a gas compressor with a variable diffuser system capable of suppressing stall and surge. The gas compressor includes i) an impeller fixed to a rotation shaft and having a plurality of blades each including a wing surface and an edge surface on an outer circumferential surface thereof; ii) a shroud surrounding the wing surface; iii) a ring valve installed on a diffuser passage connected with an outlet of the impeller and moving in a direction parallel to the rotation shaft to open and close the diffuser passage; iv) a plurality of veins installed in a circumferential direction of the diffuser passage outside the ring valve in the diffuser passage; and v) an actuator coupled with the ring valve and the plurality of veins to sequentially control movement of the ring valve and rotational angles of the veins.

1 . A gas compressor, comprising:
 an impeller fixed to a rotation shaft and having a plurality of blades each including a wing surface and an edge surface on an outer circumferential surface thereof;   a shroud surrounding the wing surface and having an outer wall parallel to the edge surface; and   a ring valve installed on a diffuser passage connected with an outlet of the impeller to open and close the diffuser passage and maintaining a gap from the end of the impeller in a radial direction of the impeller,   wherein the ring valve slidably moves on the outer wall of the shroud while contacting the outer wall of the shroud.   
     
     
         2 . The gas compressor of  claim 1 , wherein:
 the ring valve maintains a gap G of a condition described below from the end of the impeller in the radial direction of the impeller,
   0.002D≦G≦0.0080D
 
   wherein, D represents a diameter (mm) at the outlet of the impeller.   
     
     
         3 . The gas compressor of  claim 2 , further comprising:
 a plurality of veins installed in a circumferential direction of the diffuser passage outside the ring valve in the diffuser passage.   
     
     
         4 . A gas compressor, comprising:
 an impeller fixed to a rotation shaft and having a plurality of blades each including a wing surface and an edge surface on an outer circumferential surface thereof;   a shroud surrounding the wing surface;   a ring valve installed on a diffuser passage connected with an outlet of the impeller and moving in a direction parallel to the rotation shaft to open and close the diffuser passage;   a plurality of veins installed in a circumferential direction of the diffuser passage outside the ring valve in the diffuser passage and each having a vein shaft; and   an actuator coupled with the ring valve and the plurality of vein shafts to sequentially control movement of the ring valve and rotational angles of the veins.   
     
     
         5 . The gas compressor of  claim 4 , wherein:
 the ring valve maintains a gap G of a condition described below from the end of the impeller in the radial direction of the impeller,
   0.002D≦G≦0.0080D
 
   wherein, D represents a diameter (mm) at the outlet of the impeller.   
     
     
         6 . The gas compressor of  claim 5 , wherein:
 an outer wall of the shroud is parallel to the edge surface and the ring valve slidably moves on the outer wall of the shroud while contacting the outer wall of the shroud.   
     
     
         7 . The gas compressor of  claim 6 , wherein:
 in the impeller, spaces among the blades are in communication with each other over the wing surface inside the shroud.   
     
     
         8 . The gas compressor of  claim 6 , wherein:
 in the impeller, the spaces among the blades are separated from each other by a cover plate on the wing surface.   
     
     
         9 . The gas compressor of  claim 4 , wherein:
 the actuator includes   an inner guide ring surrounding the vein shaft;   a plurality of ball levers penetrating the inner guide ring and the vein shaft in the radial direction of the impeller to couple the inner guide ring and the vein shaft with each other;   an outer guide ring surrounding the inner guide ring, integrally connected with the ring valve by a connector, and having a slant sliding hole; and   a fixing pin fixed to the inner guide ring through the slant sliding hole,   wherein the gas compressor further includes a diffuser frame supporting the vein shaft, the inner guide ring, and the ring valve.   
     
     
         10 . The gas compressor of  claim 9 , wherein:
 the vein shaft has a cavity penetrating the vein shaft in the radial direction of the impeller and the inner guide ring has a plurality of openings facing the cavity in the radial direction of the impeller.   
     
     
         11 . The gas compressor of  claim 10 , wherein:
 each of the plurality of ball levers includes a ball member closely attached to a side wall of the opening of the inner guide ring and a support member inserted to the cavity to be fixed to the vein shaft.   
     
     
         12 . The gas compressor of  claim 9 , wherein:
 the actuator further includes   a stop member controlling a rotational speed of the inner guide ring;   a control handle fixed to the outer guide ring; and   an elastic member installed between the diffuser frame and the fixing pin.   
     
     
         13 . The gas compressor of  claim 12 , wherein:
 the stop member includes   a pair of first bars positioned with a distance in the circumferential direction on one surface of the inner guide ring; and   a second bar fixed to the diffuser frame and protruding so that a part thereof is positioned between the pair of first bars.   
     
     
         14 . The gas compressor of  claim 4 , wherein:
 the actuator includes   a link member fixed to the vein shaft;   a guide shaft fixed to the link member with a distance from the vein shaft; and   a control member rotating the vein shaft by moving the guide shaft while forming a first guide groove receiving the guide shaft on one surface thereof.   
     
     
         15 . The gas compressor of  claim 14 , wherein:
 the first guide groove is formed in the radial direction of the impeller, and   the control member further includes a second guide groove formed in a circumferential direction of the control member while being linked with the first guide groove.   
     
     
         16 . The gas compressor of  claim 15 , further comprising:
 a diffuser frame supporting the ring valve, and the vein shaft and the control member while surrounding the ring valve,   wherein in the diffuser frame, the slant sliding hole is formed in a region overlapping with the ring valve.   
     
     
         17 . The gas compressor of  claim 16 , wherein:
 the control member further includes a third guide groove formed on an inner surface of the control member while being linked with the second guide groove, and   the actuator further includes a fixing key of which one end is fixed to the ring valve by penetrating the slant sliding hole and the other end is received in the third guide groove.   
     
     
         18 . The gas compressor of  claim 16 , wherein:
 in the diffuser frame, a plurality of vein holes which the vein shaft penetrates are formed in a direction parallel to the rotation shaft and the slant sliding hole is spaced apart from the vein hole between two adjacent vein holes.   
     
     
         19 . The gas compressor of  claim 14 , wherein:
 the control member is connected with a control unit sensing an operational condition of the gas compressor to be operated by a command from the control unit.   
     
     
         20 . The gas compressor of  claim 4  wherein:
 the actuator includes 
 a first actuator coupled with the plurality of vein shafts to control the rotational angles of the veins; and 
 a second actuator coupled with the ring valve to control the movement of the ring valve, and 
 the first actuator includes 
 a link member fixed to the vein shaft; 
 a guide shat fixed to the link member with a distance from the vein shaft; and 
 a control member rotating the vein shaft by moving the guide shaft while forming the first guide groove receiving the guide shaft on one surface thereof. 
 
     
     
         21 . The gas compressor of  claim 20 , wherein:
 the first guide is formed in the radial direction of the impeller, and   the control member further includes a second guide groove formed in the circumferential direction of the control member while being linked with the first guide groove.   
     
     
         22 . The gas compressor of  claim 20 , wherein:
 the ring valve has an extension ring on an outer surface thereof, and   the second actuator includes   a first nozzle spraying compressed air to the one surface of the extension ring toward the diffuser passage; and   a second nozzle spraying compressed air to one opposite surface of the extension ring which is faraway from the diffuser passage.   
     
     
         23 . The gas compressor of  claim 22 , further comprising:
 a top cover installed between the diffuser frame and the ring valve,   wherein the first nozzle is formed throughout the top cover and the diffuser frame and the second nozzle is formed on the top cover.   
     
     
         24 . The gas compressor of  claim 22 , wherein:
 the control member, and the first and second nozzles are connected with the control unit sensing the operational condition of the gas compressor to be operated by the command from the control unit.   
     
     
         25 . A method for controlling a flow rate of a gas compressor including a ring valve installed in a diffuser passage connected with an outlet of an impeller, a plurality of veins installed in a circumferential direction of the diffuser passage outside the ring valve, vein shafts fixed to the plurality of veins, respectively, and an actuator coupled with the ring valve and the vein shaft, the method comprising:
 sealing the diffuser passage by closing the ring valve in initial operation and reducing an area of the diffuser passage outside the ring valve by closing the plurality of veins;   opening the diffuser passage by opening the ring valve for rated operation; and   increasing the area of the diffuser passage outside the ring valve by opening the plurality of veins.   
     
     
         26 . The method of  claim 25 , further comprising:
 for stopping the operation after the increasing of the area of the diffuser passage,   reducing the area of the diffuser passage outside the ring valve by closing the plurality of veins; and   sealing the diffuser passage by closing the ring valve.