Roto-dynamic pump with a backflow recirculator

Claim 1

A roto-dynamic pump comprising: (a) a housing having a pump chamber, a leading edge region upstream of the pump chamber, an inlet region upstream of the leading edge region permitting fluid to enter the pump and an outlet region downstream of the pump chamber permitting fluid to discharge from the pump; (b) a roto-dynamic means in the pump chamber for pumping fluid entering the structure wherein the roto-dynamic means has a leading edge; (c) a first annular slot substantially parallel to the flow of fluid in the leading edge region for collecting sufficient swirling backflow fluid caused by the roto-dynamic means to prevent cavitation surging of the pump; (d) an annulus for removing the swirl from the collected fluid wherein the annulus comprises straightening vanes and wherein the length of the annulus is at least about three-fourths the diameter of the leading edge region; and (e) a second annular slot for returning the straightened fluid into the inlet region at a direction substantially perpendicular to that of the incoming fluid in the inlet region.