US Patent 7798772 Centrifugal pump intake channel

A centrifugal pump with a housing having one or more impellers having an axial or semiaxial, open or closed design disposed therein and an intake channel mounted upstream of the first impeller. A plurality of grooves that are distributed around the circumference and extend in the direction of flow are arranged within the wall area of the intake channel. In the housing wall of the intake channel there is a closed annular wall area constructed between a point of entry of the first impeller and the proximate ends of the grooves, whereby the grooves are operatively connected exclusively with the space in the intake channel.