Patent ID: 7476081

Claim:
A centrifugal compressing apparatus comprising an impeller having a hub having a hub surface and an impeller blade extending along said hub surface, said impeller having an impeller flow entrance and an impeller flow exit, and wherein: said blade has a front edge at said impeller flow entrance and a rear edge at said impeller flow exit; said blade has a blade height from said hub surface that decreases gradually from said front edge thereof to said rear edge thereof; and an absolute value of a rate of change of said blade height is larger at a portion adjacent to said rear edge than other portions of said blade, wherein points and lines below are defined in a meridional surface: said blade has a shroud line along a shroud surface of said blade to be positioned opposite a casing; a point P is an intersection of said shroud line with said rear edge of said blade, said rear edge having a length forming a flow exit width of said impeller; and a tangent line, extending from said point P and having a point of tangency to a curve of said shroud line spaced from said point P, has a convex blade portion on a side of said tangent line distal from said hub, wherein said hub has a hub line along which said blade extends along said hub surface; a point Q is an intersection of said rear edge of said blade with said hub line; and a radial line, radial with respect to an axis of rotation of said hub, extending radially from said point Q toward the axis of rotation of said hub, has a convex blade portion on a side of said radial line proximal to said hub.