Centrifugal compressor

Abstract

Provided is a centrifugal compressor in which a malfunction such as shaft vibration due to rotating stall is suppressed, and degradation of performance due to friction losses or the like is suppressed. In a centrifugal compressor ( 10 ) including a diffuser section ( 15 ) for circulating fluid discharged from an impeller ( 13 ), a flow path width W 2 of the diffuser section ( 15 ) at an inflow position where the fluid flows in the diffuser section ( 15 ) is narrower than a flow path width W 1 of the impeller ( 13 ) at a discharge position where the fluid is discharged from the impeller ( 13 ), and a flow path width enlarged section ( 15 c) wider than the flow path width W 1 of diffuser section ( 15 ) at the inflow position is provided on a downstream side with respect to the inflow position of the diffuser section ( 15 ).

1 . A centrifugal compressor comprising:
 an impeller that is rotatable around an axis, and discharges fluid, which flows in an axial direction along the axis, in a direction inclined from the axial direction;   a casing section that houses the impeller; and   a diffuser section that circulates forms a diffuser flow path for allowing the fluid discharged from the impeller to circulate, wherein   the impeller includes a hub and a shroud that are arranged along the axial direction side by side, and a plurality of blades that are arranged between the hub and the shroud, the plurality of blades partitioning a space defined by an inner wall of the hub and an inner wall of the shroud to form a plurality of discharge flow paths,   a flow path width of the diffuser section at an inflow position where the fluid flows in the diffuser section is narrower than a flow path width of the impeller at a discharge position where the fluid discharges from the impeller,   a hub side wall of the diffuser section at the inflow position is disposed on a side closer to a center of the diffuser flow path than an extension line of the inner wall of the hub at the discharge position toward the diffuser section,   a shroud side wall of the diffuser section at the inflow position is disposed on a side closer to a center of the diffuser flow path than an extension line of the inner wall of the shroud at the discharge position toward the diffuser section, and   a flow path width enlarged section wider than the flow path width of the diffuser section at the inflow position is provided on a downstream side with respect to the inflow position of the diffuser section.   
     
     
         2 . The centrifugal compressor according to  claim 1 , wherein
 the diffuser section is defined by a hub side wall provided on a side of the hub, and a shroud side wall provided on a side of the shroud,   the hub side wall at the flow path width enlarged section is disposed in a direction in which the flow path width of the diffuser section enlarges with respect to the hub side wall at the inflow position, and   the shroud side wall at the flow path width enlarged section is disposed in a direction in which the flow path width of the diffuser section enlarges with respect to the shroud side wall at the inflow position.   
     
     
         3 . The centrifugal compressor according to  claim 1 , wherein
 the diffuser section is defined by a hub side wall provided on a side of the hub, and a shroud side wall provided on a side of the shroud, and   the hub side wall at the flow path width enlarged section is disposed in a direction in which the flow path width of the diffuser section enlarges with respect to the hub side wall at the inflow position.   
     
     
         4 . The centrifugal compressor according to  claim 1 , wherein
 the diffuser section is defined by a hub side wall provided on a side of the hub, and a shroud side wall provided on a side of the shroud, and   the shroud side wall at the flow path width enlarged section is disposed in a direction in which the flow path width of the diffuser section enlarges with respect to the shroud side wall at the inflow position.   
     
     
         5 . The centrifugal compressor according to  claim 2 , wherein
 a shape of the hub side wall is a tapered shape in which the flow path width gradually enlarges along a circulating direction of the fluid at an intermediate position between the inflow position of the diffuser section and the flow path width enlarged section, and   a shape of the shroud side wall is a tapered shape in which the flow path width gradually enlarges along the circulating direction of the fluid at the intermediate position of the diffuser section.   
     
     
         6 . The centrifugal compressor according to  claim 3 , wherein
 a shape of the hub side wall is a tapered shape in which the flow path width gradually enlarges along a circulating direction of the fluid at an intermediate position between the inflow position of the diffuser section and the flow path width enlarged section.   
     
     
         7 . The centrifugal compressor according to  claim 4 , wherein
 a shape of the shroud side wall is a tapered shape in which the flow path width gradually enlarges along a circulating direction of the fluid at an intermediate position between the inflow position of the diffuser section and the flow path width enlarged section.   
     
     
         8 . The centrifugal compressor according to  claim 2 , wherein
 a shape of the hub side wall is a stepped shape in which the flow path width enlarges along a circulating direction of the fluid stepwise at an intermediate position between the inflow position of the diffuser section and the flow path width enlarged section, and   a shape of the shroud side wall is a stepped shape in which the flow path width enlarges along the circulating direction of the fluid stepwise at the intermediate position of the diffuser section.   
     
     
         9 . The centrifugal compressor according to  claim 3 , wherein
 a shape of the hub side wall is a stepped shape in which the flow path width enlarges along a circulating direction of the fluid stepwise at an intermediate position between the inflow position of the diffuser section and the flow path width enlarged section.   
     
     
         10 . The centrifugal compressor according to  claim 4 , wherein
 a shape of the shroud side wall is a stepped shape in which the flow path width enlarges along a circulating direction of the fluid stepwise at an intermediate position between the inflow position of the diffuser section and the flow path width enlarged section.   
     
     
         11 . The centrifugal compressor according to  claim 1 , wherein
 a ratio of the flow path width of the diffuser section at the inflow position to the flow path width of the impeller at the discharge position is not less than 0.5 and less than 0.8.   
     
     
         12 . The centrifugal compressor according to  claim 1 , wherein
 a ratio of a flow path width of the diffuser section at the flow path width enlarged section to the flow path width of the impeller at the discharge position is not less than 0.8 and not more than 1.0.   
     
     
         13 . The centrifugal compressor according to  claim 1 , wherein
 the impeller discharges the fluid, which flows along the axial direction, in a direction orthogonal to the axial direction.   
     
     
         14 . The centrifugal compressor according to  claim 1 , wherein
 a flow rate coefficient is not less than 0.01 and not more than 0.05.