Centrifugal compressor

Abstract

In order to reduce the rotating stall onset flowrate, this centrifugal compressor comprises: a vaneless diffuser ( 12 ) provided on a discharge outlet ( 6 B) side of an impeller ( 6 ); and a fluid circulation flow path ( 21 ) having an inlet ( 21 A) that opens into a first wall section ( 22 ) of a hub casing ( 2 B) forming the vaneless diffuser ( 12 ) and also having an outlet ( 21 B) that opens into a second wall section ( 23 ) of the hub casing ( 2 B) facing a hub disk ( 6 C) rear surface in the impeller ( 6 ). As a result of causing the first wall section ( 22 ) to protrude on to a wall section ( 31 ) side of the shroud casing ( 2 A), the flow path width (D) of the vaneless diffuser ( 12 ) is smaller than the width (W) of the discharge outlet ( 6 B) in the impeller ( 6 ). In addition, the hub casing ( 2 B) comprises an inclined wall section ( 24 ) having a protruding end ( 24 A) between the discharge outlet ( 6 B) of the impeller ( 6 ) and the inlet of the vaneless diffuser ( 12 ), said inclined wall section ( 24 ) connecting the second wall section ( 23 ) and the first wall section ( 22 ).

1 . A centrifugal compressor, comprising:
 a vaneless diffuser which is provided on an outlet side of an impeller; and   a fluid circulation flow path which includes a fluid inlet which opens into a first wall section of a hub casing forming the vaneless diffuser and a fluid outlet which opens into a second wall section of the hub casing facing a back face of a hub disk in the impeller,   wherein in the vaneless diffuser, at least the first wall section of the hub casing protrudes toward a wall section side of a shroud casing facing the first wall section, a flow path width of the vaneless diffuser is formed to be smaller than an outlet width of the impeller, and the hub casing includes an inclined wall section which has a portion between the outlet of the impeller and the inlet of the vaneless diffuser as a protruding end and connects the second wall section and the first wall section.   
     
     
         2 . The centrifugal compressor according to  claim 1 ,
 wherein in the inclined wall section, the trailing end which is continued to the first wall section is disposed to be closer to the outside in a radial direction than an end section on the inside in the radial direction of the impeller in the wall section of the shroud casing.   
     
     
         3 . The centrifugal compressor according to  claim 1 ,
 wherein the first wall section of the hub casing further protrudes toward the wall section side of the shroud casing than a hub-side extension line which extends to the outside in the radial direction from the outlet of the impeller, and a hub-side protrusion length from the hub-side extension line to the first wall section is 50% or less of the outlet width of the impeller.   
     
     
         4 . The centrifugal compressor according to  claim 1 ,
 wherein the wall section of the shroud casing further protrudes toward the first wall section side of the hub casing than a shroud-side extension line which extends to the outside in the radial direction from the outlet of the impeller, and a shroud-side protrusion length from the shroud-side extension line to the wall section is 20% or less of the outlet width of the impeller.   
     
     
         5 . The centrifugal compressor according to  claim 2 ,
 wherein the first wall section of the hub casing further protrudes toward the wall section side of the shroud casing than a hub-side extension line which extends to the outside in the radial direction from the outlet of the impeller, and a hub-side protrusion length from the hub-side extension line to the first wall section is 50% or less of the outlet width of the impeller.   
     
     
         6 . The centrifugal compressor according to  claim 2 ,
 wherein the wall section of the shroud casing further protrudes toward the first wall section side of the hub casing than a shroud-side extension line which extends to the outside in the radial direction from the outlet of the impeller, and a shroud-side protrusion length from the shroud-side extension line to the wall section is 20% or less of the outlet width of the impeller.   
     
     
         7 . The centrifugal compressor according to  claim 3 ,
 wherein the wall section of the shroud casing further protrudes toward the first wall section side of the hub casing than a shroud-side extension line which extends to the outside in the radial direction from the outlet of the impeller, and a shroud-side protrusion length from the shroud-side extension line to the wall section is 20% or less of the outlet width of the impeller.