Water-Ring Pump

a mechanical vacuum pump containing an eccentrically-seated rotating ring with radial blades. The working fluid (water) is thrown to the wall of the pump by centrifugal forces, thus forming a ring of water and the working chamber of the pump (the water-free crescent-shaped space within the ring). Gas is pumped out as a result of the changes in volume of each of the spaces between the rotor blades.