SCREW CENTRIFUGAL PUMP Russian patent published in 2008 - IPC F04D9/04 F04D29/66 

FIELD: engines and pumps.

SUBSTANCE: screw centrifugal pump incorporates centrifugal two-way suction impeller 3 and two prescrews 4 and 5 fitted on shaft 2 in casing 1. The screws have opposing screw blades 6 with a cylindrical inlet section changing into section 8 with the diameter smoothly decreasing towards the outlet. Screws 4 and 5 are fitted into profiled bushes 9. Each side of centrifugal impeller 3 represents an axioradial wheel, the impeller inlet axial part outer diameter being equal to the inlet diameter of screws 4 and 5. Every screw blade 6 pitch smoothly increases towards the outlet. The blade angle of screws 4 and 5 increases from 9° to 15° at the inlet to 15° to 25° at the outlet. The grate density makes 1 to 1.5 at the inlet of screws 4 and 5. The blade angle at the axioradial wheel inlet axial part is equal to that of blades 6 of screws 4 or 5 at the outlet. The grate density at the axioradial wheel inlet section makes 1 to 1.5. The number of the axioradial wheel blades varies at every section.

EFFECT: higher efficiency, improved cavitation properties and lower pressure pulsations.

2 cl, 8 dwg