Multi-stage centrifugal compressor

Abstract

A multi-stage centrifugal compressor, including: a rotary electric motor inside a motor housing and coupled to a motor shaft; two radial compression stages comprising back-to-back bladed compression impellers; an outlet manifold in communication with second exhaust flow paths; at least one inter-stage flow passage comprising: a main channel passing through the motor housing and opening onto a first lateral face of the motor housing; an intermediate channel in sealed communication with the main channel and passing through a spacer inserted between a second lateral face of the motor housing and a second cowl; and a secondary channel formed in the second cowl and opening opposite a second bladed compression impeller.

1 . A multi-stage centrifugal compressor, comprising:
 a rotary electric motor arranged inside a motor housing having two opposite lateral faces, namely a first lateral face and a second lateral face;   a motor shaft driven in rotation around a motor axis by the rotary electric motor and having a first section and a second section opposite each other extending on either side of the rotary electric motor and of the two respective lateral faces of the motor housing;   a first radial compression stage comprising a first bladed compression impeller coupled in rotation to the first section of the motor shaft and having a first upstream end in communication with a gaseous fluid inlet, and a first downstream end facing the side of the first lateral face of the motor housing;   a second radial compression stage comprising a second bladed compression impeller coupled in rotation to the second section of the motor shaft and having a second upstream end and a second downstream end facing the side of the second lateral face of the motor housing so that the first bladed compression impeller and the second bladed compression impeller are arranged in a back-to-back configuration;   an outlet manifold secured to the motor housing and in communication with the second downstream end of the second bladed compression impeller;   a first cowl covering the first radial compression stage;   a second cowl covering the second radial compression stage; and   at least one inter-stage flow passage of gaseous fluid communicating the first downstream end of the first bladed compression impeller with the second upstream end of the second bladed compression impeller;   wherein the at least one inter-stage flow passage of gaseous fluid has the following successive channels:   a main channel passing through the motor housing and provided with a main inlet orifice opening onto the first lateral face of the motor housing and in communication with the first downstream end of the first bladed compression impeller;   an intermediate channel in sealed communication with the main channel and passing through a spacer inserted between the second lateral face of the motor housing and the second cowl; and   a secondary channel formed in the second cowl and which is in sealed communication with the intermediate channel, wherein the secondary channel has a secondary outlet orifice opening opposite the second upstream end of the second bladed compression impeller.   
     
     
         2 . The multi-stage centrifugal compressor according to  claim 1 , wherein a first diffuser surrounds the first downstream end of the first bladed compression impeller and is provided with first fins distributed around the first downstream end of the first bladed compression impeller, wherein the first fins are separated by first exhaust flow paths, and wherein the main inlet orifice of the main channel opens into one first exhaust flow path, between two first fins of the first diffuser. 
     
     
         3 . The multi-stage centrifugal compressor according to  claim 2 , wherein the first fins of the first diffuser are:
 secured to the first lateral face of the motor housing, and the first cowl bears against the first fins; or are   secured to the first cowl, and the first fins bear against the first lateral face of the motor housing; or are   independent of the first cowl, and the motor housing, by being interposed between the first cowl and the first lateral face of the motor housing.   
     
     
         4 . The multi-stage centrifugal compressor according to  claim 1 , wherein the spacer is:
 secured to the second lateral face of the motor housing, and the second cowl bears against the spacer; or is   secured to the second cowl, and the spacer bears against the second lateral face of the motor housing; or is   independent of the motor housing and the second cowl, by being interposed between the second lateral face of the motor housing and the second cowl.   
     
     
         5 . The multi-stage centrifugal compressor according to  claim 1 , wherein a second diffuser surrounds the second downstream end of the second bladed compression impeller and is provided with second fins distributed around the second downstream end of the second bladed compression impeller and interposed between the second lateral face of the motor housing and the second cowl, wherein the second fins are separated by second exhaust flow paths, and wherein the intermediate channel is arranged through one of the second fins which thus forms the spacer. 
     
     
         6 . The multi-stage centrifugal compressor according to  claim 5 , wherein the second fins of the second diffuser are:
 secured to the second lateral face of the motor housing, and the second cowl bears against the second fins; or are   secured to the second cowl, and the second fins bear against the second lateral face of the motor housing; or are   independent of the motor housing and the second cowl, by being interposed between the second lateral face of the motor housing and the second cowl.   
     
     
         7 . The multi-stage centrifugal compressor according to  claim 1 , wherein:
 the motor housing is in one piece and the main channel passes through the motor housing, or   the motor housing comprises an inner sleeve and an outer sleeve fitted into one another and the main channel passes through the motor housing in an interface zone between the inner sleeve and the outer sleeve.   
     
     
         8 . The multi-stage centrifugal compressor according to  claim 1 , wherein:
 the second cowl is in one piece and the secondary channel is provided in the second cowl, or   the second cowl comprises an inner part and an outer part assembled on one another and the secondary channel is provided in the second cowl in an interface zone between the inner part and the outer part.   
     
     
         9 . The multi-stage centrifugal compressor according to  claim 1 , further comprising a cooling circuit arranged in the motor housing for a circulation of coolant inside the motor housing. 
     
     
         10 . The multistage centrifugal compressor according to  claim 9 , wherein the cooling circuit has one or more sections contiguous to the main channel of the at least one inter-stage flow passage of gaseous fluid or one of the at least one inter-stage flow passage of gaseous fluid. 
     
     
         11 . The multi-stage centrifugal compressor according to  claim 1 , wherein a plurality of inter-stage flow passages of gaseous fluid are provided. 
     
     
         12 . The multi-stage centrifugal compressor according to  claim 2 , wherein the main channel of the at least one inter-stage flow passage of gaseous fluid opens into distinct first exhaust flow paths. 
     
     
         13 . The multi-stage centrifugal compressor according to  claim 12 , wherein the first diffuser comprises N first fins separated by N first exhaust flow paths wherein N is an integer greater than 2, and N inter-stage flow passages of gaseous fluid are provided with N main channels which open into the N respective first exhaust flow paths. 
     
     
         14 . The multi-stage centrifugal compressor according to  claim 11 , wherein the intermediate channel of the at least one various inter-stage flow passage of gaseous fluid passes through distinct spacers. 
     
     
         15 . The multi-stage centrifugal compressor according to  claim 5 , wherein the at least one inter-stage flow passage of gaseous fluid is a plurality of inter-stage flow passages of gaseous fluid and intermediate channels of the different inter-stage flow passages of gaseous fluid of the plurality of inter-stage flow passages of gaseous fluid pass through distinct second fins. 
     
     
         16 . A multi-stage centrifugal compressor according to  claim 15 , wherein the second diffuser comprises N second fins wherein N is an integer greater than 2, and there are N inter-stage flow passages of gaseous fluid with N intermediate channels passing through the respective N second fins. 
     
     
         17 . The multistage centrifugal compressor according to  claim 1 , wherein the main channel of the at least one inter-stage flow passage of gaseous fluid or of one of the at least inter-stage flow passage of gaseous fluid extends along an axial direction parallel to the motor axis or substantially parallel to the motor axis. 
     
     
         18 . The multi-stage centrifugal compressor according to  claim 1 , wherein the main channel of the at least one inter-stage flow passage of gaseous fluid or of one of the at least one inter-stage flow passage of gaseous fluid has a variable cross-section along the motor axis (AM). 
     
     
         19 . The multistage centrifugal compressor according to  claim 1 , wherein the secondary channel of the at least one inter-stage flow passage of gaseous fluid or of one of the at least one inter-stage flow passage of gaseous fluid has a curved section between a corresponding intermediate channel and its secondary outlet. 
     
     
         20 . The multi-stage centrifugal compressor according to  claim 19 , wherein the curved section of the secondary channel has an angular amplitude comprised between 150 and 180 degrees, to define a reversal of flow in the secondary channel. 
     
     
         21 . The multi-stage centrifugal compressor according to  claim 1 , wherein the second cowl is closed, without a gaseous fluid introduction orifice opening into an outer face to introduce from outside a gaseous fluid in the second of radial compression stage. 
     
     
         22 . The multi-stage centrifugal compressor according to  claim 1 , wherein the second cowl is fixed to the motor housing or to the outlet manifold. 
     
     
         23 . The multi-stage centrifugal compressor according to  claim 1 , wherein the outlet manifold has an outlet volute in communication with the second downstream end of the second bladed compression impeller.