Abstract: A centrifugal compressor includes: an impeller which is allowed to rotate around an axis; a casing in which the impeller is accommodated and a guide flow path guiding fluid to the impeller is formed; and a guide vane which is disposed in the guide flow path and is extended from a hub side wall surface of the guide flow path, which is continued to a hub side of the impeller, to a shroud side wall surface of the guide flow path to a shroud side of the impeller, wherein the guide vane is twisted forward the impeller in a rotating direction thereof as close to the shroud side wall surface from the hub side wall surface.

Abstract: A centrifugal compressor includes: an impeller which is allowed to rotate around an axis; a casing in which the impeller is accommodated and a guide flow path guiding fluid to the impeller is formed; and a guide vane which is disposed in the guide flow path and is extended from a hub side wall surface of the guide flow path, which is continued to a hub side of the impeller, to a shroud side wall surface of the guide flow path to a shroud side of the impeller, wherein the guide vane is twisted forward the impeller in a rotating direction thereof as close to the shroud side wall surface from the hub side wall surface.

Abstract: The impeller includes a disc having a main surface extending outward in a radial direction toward one side in an axial direction, a plurality of blades defining a flow path extending to an outlet on one side from an inlet on the other side in the axial direction, and a cover disposed to cover the plurality of blades. At least one of an inlet side region and an outlet side region which are a connection portion between the blade and the main surface and a connection portion between the blade and the cover has a small fillet portion curved in an arc shape and having a small radius of curvature. An intermediate region formed between the inlet side region and the outlet side region has a large fillet portion having a large radius of curvature.

Abstract: A centrifugal compressor is provided with a return vane including a suction surface facing a front side in a rotation direction of a rotation shaft and a pressure surface facing a rear side. A casing includes a hub side wall surface and a shroud side wall surface that form a placement region of the return vane in the straight flow path, and an intermediate suction port formed on the shroud side wall surface, the intermediate suction port ejecting fluid guided from outside toward the straight flow path; and inside the return vane, an internal flow path is formed in which one end communicates with the intermediate suction port and another end is an outlet port that opens to the suction surface of the return vane.

Abstract: A multi-stage centrifugal compressor according to at least one embodiment includes: multiple stages of impellers arranged in an axial direction; a casing surrounding the impellers; and a diffuser channel for guiding a working fluid discharged from the impellers outward in a radial direction. In a cross-section along the axial direction, a first diffuser wall surface on a hub side of a pair of diffuser wall surfaces that are opposed in the axial direction across the diffuser channel has a retreating surface retreating toward the hub side from a connection position with a downstream end of a first upstream wall surface to a radially outer side with respect to a tangential direction of the first upstream wall surface at the downstream end of the first upstream wall surface, the first upstream wall surface being positioned upstream of the first diffuser wall surface and connected to the first diffuser wall surface.

Abstract: The impeller includes a disc having a main surface extending outward in a radial direction toward one side in an axial direction, a plurality of blades defining a flow path extending to an outlet on one side from an inlet on the other side in the axial direction, and a cover disposed to cover the plurality of blades. At least one of an inlet side region and an outlet side region which are a connection portion between the blade and the main surface and a connection portion between the blade and the cover has a small fillet portion curved in an arc shape and having a small radius of curvature. An intermediate region formed between the inlet side region and the outlet side region has a large fillet portion having a large radius of curvature.

Abstract: A centrifugal compressor is provided with a return vane including a suction surface facing a front side in a rotation direction of a rotation shaft and a pressure surface facing a rear side. A casing includes a hub side wall surface and a shroud side wall surface that form a placement region of the return vane in the straight flow path, and an intermediate suction port formed on the shroud side wall surface, the intermediate suction port ejecting fluid guided from outside toward the straight flow path; and inside the return vane, an internal flow path is formed in which one end communicates with the intermediate suction port and another end is an outlet port that opens to the suction surface of the return vane.

Abstract: A multi-stage centrifugal compressor according to at least one embodiment includes: multiple stages of impellers arranged in an axial direction; a casing surrounding the impellers; and a diffuser channel for guiding a working fluid discharged from the impellers outward in a radial direction. In a cross-section along the axial direction, a first diffuser wall surface on a hub side of a pair of diffuser wall surfaces that are opposed in the axial direction across the diffuser channel has a retreating surface retreating toward the hub side from a connection position with a downstream end of a first upstream wall surface to a radially outer side with respect to a tangential direction of the first upstream wall surface at the downstream end of the first upstream wall surface, the first upstream wall surface being positioned upstream of the first diffuser wall surface and connected to the first diffuser wall surface.