Pipe diffuser of centrifugal compressor

A pipe diffuser of a centrifugal compressor, comprising:

• a plurality of diffuser pipes arranged circumferentially at a prescribed interval around an impeller of a centrifugal compressor, each diffuser pipe defining a diffuser passage configured to convert a radial flow of working fluid received from the impeller into an axial flow substantially in parallel with a central axial line of the impeller,
• the diffuser passage including
• an inlet passage portion including a diffuser inlet opposing an outer periphery of the impeller,
• an outlet passage portion including a diffuser outlet opening in an axial direction of the impeller, the outlet passage portion having an oval cross section elongated in a substantially circumferential direction of the impeller, and
• a curved passage portion connecting the inlet passage portion and the outlet passage portion to each other, the diffuser passage having a cross sectional area progressively increasing from the diffuser inlet to the diffuser outlet,
• wherein a part of each diffuser pipe defining the outlet passage portion is provided with a bulging part that bulges into the diffuser passage from a radially inner side thereof with respect to the impeller.