Diffuser for a centrifugal compressor

A diffuser for a centrifugal compressor that includes an impeller rotatably carried within a casing, said diffuser comprising:

• a plurality of substantially linearly-extending diffuser passageways having respective longitudinal axes disposed tangentially to an imaginary circle having its center coincident with the impeller axis, the diffuser passageways including a diffuser inlet region commencing adjacent the impeller periphery, a diffuser throat region downstream of the diffuser inlet region, and a diffuser outlet region downstream of the diffuser throat region, wherein the diffuser outlet region is defined by substantially linear wall surfaces of the diffuser panels and includes a first diffusion region and a second diffusion region, wherein the diffuser passageways are each bounded by a pair of circumferentially spaced diffuser panels having respective leading edges adjacent the impeller periphery and that lie on a diffuser leading edge circle, and having trailing edges spaced radially outwardly of and circumferentially offset from the leading edges and that lie on a diffuser trailing edge circle, wherein the wall surfaces of the diffuser panels within the second diffusion region define a second divergence included angle, including a flow divider positioned within the second diffusion region;
• and
• at least one ridge extending substantially longitudinally relative to and within the diffuser inlet region between the impeller periphery and the diffuser leading edge circle, and extending inwardly into the diffuser passageway, wherein the at least one ridge is positioned between and is spaced from the leading edges of adjacent diffuser panels for mixing of air leaving the impeller and entering the diffuser passageway to reduce boundary layer buildup upstream of the diffuser throat region, wherein the diffuser flow divider is carried within an annular outlet passageway extending downstream of the diffuser outlet region.

A method for increasing the efficiency of diffusion for diffusing air that exits from the impeller of a centrifugal compressor, said method comprising:

• providing a pair of opposed ridges extending substantially longitudinally relative to and within a diffuser inlet region between the impeller periphery and an imaginary circle defined by a plurality of diffuser panel leading edges, each ridge extending partially inwardly into the diffuser inlet region for mixing of air leaving the impeller and entering the diffuser inlet region to reduce boundary layer buildup within the diffuser inlet region;
• diffusing impeller outlet air flow in a first diffusion region downstream of the diffuser inlet region through a first passageway area ratio;
• dividing outlet flow from the first diffusion region into two flows in a pair of second diffusion regions downstream of the first diffusion region;
• and
• diffusing flow within the first diffusion region and within each second diffusion region through substantially the same passageway area ratio.