Abstract: A multistage axial flow pump or compressor comprises at least one stage (10) including a rotor (16) and a stator (20). The rotor (16) is arranged to impart whirl in one direction, while the stator (20) is arranged to impart whirl in the opposite direction. This arrangement is useful in providing comparatively high stage pressures for a given rotor tip velocity with relatively low rotor vane hydraulic loadings. The arrangement is also useful in pumping multiphase fluids.

Abstract: A pump for low head duties includes an impeller portion and a diffuser portion which together define the entire liquid retaining and guidance means between the inlet and the outlet, the impeller serving to raise liquid from a lower reservoir and having a plurality of spiral passages therethrough in which, in operation, a free liquid surface vortex is enabled to form, the diffuser portion leading from the impeller outlet having a rotatable section and an upwardly increasing diameter. The impeller comprising vanes having leading edges extending downwardly and outwardly to provide a liquid inlet providing a substantially unobstructed entry to the vanes and automatic control of the quantity of liquid pumped according to the level of liquid in the lower reservoir. The diffuser portion is driven separately at a speed less than the impeller.