Patent attributes
A centrifugal compressor includes an impeller including a hub and a plurality of blades disposed on an outer peripheral surface of the hub at intervals in a circumferential direction, and a casing accommodating the impeller and defining an inlet passage for introducing air along an axial direction of the impeller. An inner peripheral surface of the inlet passage includes a narrowed portion, and an inclined portion connected to a downstream side of the narrowed portion and having a radial distance from a rotational axis of the impeller gradually increasing toward the vicinity of tips of leading edges of the blades. Further, 0.01R1≤σ≤0.1R1 is satisfied, where R1 is radial distance between a downstream end of the inclined portion and the rotational axis, R2 is radial distance between a downstream end of the narrowed portion and the rotational axis, and σ is constriction amount which is a difference between R1 and R2.
