Abstract: A pipe diffuser is used in a centrifugal compressor in such a way as to obtain high efficiency over a broad operating range. The number of channels in the pipe diffuser is limited such that the wedge angle is relatively large and therefore not susceptible to flow separation at the leading edges thereof. The vaneless space between the impeller and the leading edge circle of the diffuser is limited in its radial depth such that the flow separations are further inhibited. Finally, the impeller has a relatively high backsweep such that the absolute flow exit angle is relatively low, thereby reducing the sensitivity to lower flow conditions.

Abstract: In a pipe diffuser, a plurality of circumferentially spaced generally radially extending passages, are formed in a disc in such a way as to eliminate the need for plugs to prevent wandering of the drill bit during the drilling process. The passages are drilled, but not to the point of any substantial intersection between the adjacent passages. Material is then removed from the inner periphery of the disc to the radial extent of a leading edge circle defined by the leading edge of the islands between the passages. The resulting structure is substantially equivalent in performance but is obtained with a much easier process.