DIFFUSER AND MANUFACTURE THEREOF

PROBLEM TO BE SOLVED: To facilitate manufacture by mechanical work, and reduce pressure loss in the vicinity of a wall surface by curvedly forming a front edge of a diffuser symmetrically with a cross section of a center in a blade width direction of an outlet passage, in the diffuser which is arranged between wall surfaces of the outlet passage of a centrifugal compressor, and which is composed of a plurality of blades. SOLUTION: In a centrifugal compressor, air which is sucked and compressed in impellers which rotate with high speed flows out in a centrifugal direction bypassing a diffuser 2, and is supplied to an used place out of a system while guiding by a scroll. The diffuser 2 is composed of a plurality of blades arranged at a prescribed clearance along a circumferential direction, a shape of a front edge 2a of the diffuser 2 is formed in a circular arc shape vertically and symmetrically in a passage center part C. i.e., a blade width direction from a part of 1/2 of a width H of the diffuser 2. A cross sectional shape of a direction perpendicular to the front edge 2a in each part of a blade width direction is formed so as to be in a same shape as the cross sectional shape of the passage center part C. It is thus possible to reduce pressure loss, and it is also possible to improve an operation efficiency.