a pump having centrifugal and vortex impellers mounted on a common rotor member . impellers are mounted on opposite sides of rotor and make maximum use of rotor diameter . fluid follows a serial path through the centrifugal and vortex impellers . the vortex impellers rotate in a vortex channel divided into one or more sections , plural sections of which may be arranged in parallel flow relation . the casing surrounding the rotor member may form the necessary inlet , outlet , and internal fluid channels for the pump .