Discrete passage diffuser

Abstract

A centrifugal compressor includes an impeller and a diffuser. The impeller has an inner integral hub with vanes thereon, is adapted to rotate within an outer shroud about a central longitudinal axis, and has a defined hub-to-shroud distribution of fluid exit angles. The diffuser, downstream from the impeller, comprises a plurality of circumferentially spaced discrete passages at least partially defining fluid paths through the diffuser, and angled such that adjacent discrete passages intersect each other to form an annular semi-vaneless diffuser inlet space. The discrete passages downstream of the semi-vaneless space each have an inlet therefrom and an outlet with a greater cross-sectional area than the inlet. The intersection of the annular semi-vaneless space and each discrete passage defines a leading edge thereof. Each discrete passage is defined by a wall bounding a cross-sectional area, the wall comprising at least a first substantially rectilinear portion and a second opposed convexly curved portion; the first substantially rectilinear portion is adjacent the hub of the impeller and the second opposed convexly curved portion is adjacent the outer shroud. The leading edge of each discrete diffuser passage provides a close incidence angle match with the fluid exit angles of the impeller.