Patent ID: 7628583

Claim:
A centrifugal compressor comprising: an impeller having a hub mounted for rotation about a compressor central axis within an outer shroud, the impeller having an impeller exit; and a diffuser mounted downstream of the impeller exit, the diffuser having a plurality of circumferentially-spaced discrete passages at least partially defining fluid paths therethrough, each path having an inlet and an outlet, the discrete passages being angled relative to one another such that adjacent discrete passages intersect each other to form an annular semi-vaneless diffuser inlet space upstream of the fluid path inlets, each discrete passage having a substantially D-shaped cross-section extending between said inlet and said outlet, the D-shaped cross-section being composed of a U-shaped arcuate surface opposing a substantially flat surface, the substantially flat surface being adjacent to the hub of the impeller and extending substantially radially from the hub at an inlet of each said passage, the U-shaped arcuate surface being adjacent to the outer shroud of the impeller at the inlet of the passage and facing axially rearward towards the substantially flat surface, the intersection of adjacent D-shaped passages in the semi-vaneless space forming partial vanes on the shroud side of the diffuser by the intersection of the arcuate portions of the passages, and wherein the intersection of the discrete passages creates a leading edge having a repeated pattern of swept back portions, each portion having an S-shaped double curve comprising opposing convex and concave curved ends and a substantially straight central edge portion.