Economized Centrifugal Compressor

Abstract

A compressor ( 22; 260; 300; 400 ) has a housing assembly ( 140 ) with a suction port ( 24 ), a discharge port ( 26 ), and an economizer port ( 58 ). An impeller ( 154 ) is mounted to be driven in at least a first condition so as to draw a main flow of fluid through the suction port and discharge the fluid from the discharge port. A diffuser ( 220; 302; 402 ) has a plurality of diffuser passages ( 222; 310, 308; 403 ). Each diffuser passage has an inlet ( 224 ) positioned to receive fluid from the impeller and an outlet ( 220 ) downstream of the inlet in the first condition. One or more passages ( 230, 231, 232, 234, 236, 268; 320, 330, 332; 412 ) are positioned to draw an economizer flow of fluid from the economizer port and deliver the economizer flow downstream of the impeller inlet ( 212 ) but upstream of the diffuser passage outlets ( 226 ).

1 . A centrifugal compressor comprising:
 a housing assembly having a suction port, a discharge port, and an economizer port;   an impeller mounted to be driven in at least a first condition so as to draw a main flow of fluid in through the suction port and discharge said fluid out from the discharge port;   a diffuser having one or more diffuser passages each having an inlet positioned to receive fluid from the impeller and an outlet downstream of the inlet in the first condition; and   one or more passages positioned to draw an economizer flow of fluid from the economizer port and deliver the economizer flow between the impeller and the diffuser passage inlets.   
     
     
         2 . The compressor of  claim 1  further comprising:
 an electric motor having:
 a stator within a motor compartment of the case; and 
 a rotor within the stator, the rotor being mounted for rotation about a rotor axis. 
 
 
     
     
         3 . The compressor of  claim 1  wherein:
 the one or more passages are positioned to deliver said economizer flow of fluid through a gap between an impeller shroud and the diffuser. 
 
     
     
         4 . The compressor of  claim 1  wherein:
 the impeller shroud is a portion of the housing assembly between the impeller and the diffuser passage inlets. 
 
     
     
         5 . The compressor of  claim 1  wherein:
 the compressor is a single-stage compressor. 
 
     
     
         6 . The compressor of  claim 1  wherein:
 the one or more passages are further positioned to pass said economizer flow of fluid through a chamber along an outboard portion of an impeller shroud. 
 
     
     
         7 . A vapor compression system comprising:
 the compressor of  claim 1 ;   a first heat exchanger coupled to the discharge port to receive refrigerant driven in a downstream direction in the first operational condition of the compressor;   an expansion device downstream of the first heat exchanger;   a second heat exchanger downstream of the expansion device and coupled to the suction port to return refrigerant in the first operating condition; and   wherein an economizer flowpath branches off between the first heat exchanger and the expansion device and passes through the economizer port.   
     
     
         8 . The system of  claim 7  wherein the economizer flowpath passes:
 through an economizer expansion device; and then through a leg of an economizer heat exchanger, the leg in heat transfer relation with another leg upstream of the expansion device along the main flowpath. 
 
     
     
         9 . The system of  claim 8  wherein:
 the first heat exchanger is a heat rejection heat exchanger; and 
 the second heat exchanger is a heat absorption heat exchanger. 
 
     
     
         10 . A method for operating the compressor of  claim 1  comprising:
 driving the motor to draw the main flow of fluid in through the suction port and discharge the fluid from the discharge port; 
 drawing the economizer flow of fluid through the one or more passages; and 
 passing the economizer flow of fluid through the diffuser to merge with the main flow of fluid. 
 
     
     
         11 . The method of  claim 10  wherein:
 the compressor is used in a vapor compression system having a heat rejection heat exchanger, an expansion device, and a heat absorption heat exchanger, wherein: 
 the main flow of fluid is drawn through the suction port from the heat absorption heat exchanger; 
 the discharge flow of fluid is discharged from the discharge port to the heat rejection heat exchanger; 
 fluid from the heat rejection heat exchanger is expanded in the expansion device; 
 fluid expanded in the expansion device is delivered to the heat absorption heat exchanger; and 
 a portion of the fluid delivered to the heat rejection heat exchanger bypasses the heat absorption heat exchanger and passes as said economizer flow of fluid. 
 
     
     
         12 . The method of  claim 10  wherein:
 there is a single-stage of compression. 
 
     
     
         13 . The compressor of  claim 1  wherein:
 the compressor is a single-stage compressor. 
 
     
     
         14 . The compressor of  claim 1  wherein:
 the diffuser surrounds the impeller. 
 
     
     
         15 . The compressor of  claim 1  wherein:
 the one or more diffuser passages is a circumferential array of diffuser passages. 
 
     
     
         16 . The compressor of  claim 1  wherein:
 the diffuser is a pipe diffuser or vaned diffuser.