Abstract: An impeller for a centrifugal compressor includes a hub, several main blades mounted to the hub, and several splitter blades mounted to the hub, each splitter blade being located between adjacent main blades and being disposed from a position centered between the adjacent main blades by an amount of about 6% to about 33% of one half the angular distance between the main blades.

Abstract: A fluid shear coupling comprises a driving member having a disc-shaped portion and a driven member defining a working chamber in which the driving member is received, the two members being mounted for relative rotation about a common axis, the driven member defining an annular groove facing the side of the driving member and further defining a circumferential cavity facing the outer perimeter of the driving member, and a one-piece, L-shaped dam having a radially extending portion received within the annular groove and an axially extending portion received within the circumferential cavity, each of the radially and axially extending portions including a first ramp surface facing in one direction and a second ramp surface facing in the other direction.