Abstract: A centrifugal compressor includes a rotary shaft; a hollow casing; a first-stage inlet guide vane; a first-stage impeller; a diffuser; a return flow channel; return vanes; a second-stage inlet guide vane; and a second-stage impeller. The return vanes are arranged at predetermined intervals in a circumferential direction of the rotary shaft and a vane angle of each return vane is changed in a region from a leading edge, at which the fluid is introduced, to a predetermined position and the vane angle is maintained constant in a region from the predetermined position to a trailing edge, at which the fluid is discharged, in terms of meridian plane distance in a direction from the leading edge to the trailing edge.

Abstract: A centrifugal compressor includes a rotary shaft; a hollow casing; a first-stage inlet guide vane; a first-stage impeller; a diffuser; a return flow channel; return vanes; a second-stage inlet guide vane; and a second-stage impeller. The return vanes are arranged at predetermined intervals in a circumferential direction of the rotary shaft and a vane angle of each return vane is changed in a region from a leading edge, at which the fluid is introduced, to a predetermined position and the vane angle is maintained constant in a region from the predetermined position to a trailing edge, at which the fluid is discharged, in terms of meridian plane distance in a direction from the leading edge to the trailing edge.