Patent ID: 7021891

Claim:
An apparatus comprising: a disk having a first side, a second side, a center, an axis of rotation, and an edge; a shaft extending outward from the center, on the first side and on the second side, along the axis of rotation; and a first and second plurality of spaced-apart blades that project from the first side and the second side of the disk respectively, and the first and second plurality of spaced-apart blades radiating from proximate the shaft, defining a first and second plurality of impeller inlets, to the edge or proximate the edge, defining a first and second plurality of impeller outlets, respectively, the first and second plurality of spaced-apart blades also defining a first and second plurality of flow passages from the first and second plurality of impeller inlets to the first and second plurality of impeller outlets for the working fluid to enter the first and second plurality of impeller inlets and exit the first and second plurality of impeller outlets respectively, and the blades being further adapted to approximately equalize a combined distributed mass of the disk, the blades, and a working fluid about the axis of rotation.