Abstract: The pump comprises a housing (1) in which are installed with a radial clearance an axial-flow suction wheel (5) and an axial-flow impeller wheel (6), which wheels are mounted on a common drive shaft (4) one after the other in the direction of flow. The inside diameter of the pump housing (1) in the zone of the suction wheel (5) decreases in the direction of flow. The inside diameter of the pump housing at the entry to the suction wheel (5) is calculated from the formula:D.sub.o =D.sub.1 .multidot.K.sub.1 (C.sub.k .multidot.10.sup.-4 +2.1).sup.2The suction wheel (5) comprises a hub (11) with helical vanes (12) attached thereto. The vane setting angle increases in the direction of flow and at the entry to the suction wheel (5) it is:.beta..sub.o =(10 to 33.DELTA./D.sub.1).degree..+-.1.5,whereD.sub.o --inside diameter of the pump housing 1 at the entry to the suction wheel 5;D.sub.1 --inside diameter of the pump housing 1 at the entry to the impeller wheel 6;K.sub.1 --dimensionless coefficient of 0.17 to 0.13;C.

Abstract: The pump of the present invention has a housing which accommodates an axial impeller set on the pump drive shaft. The impeller has a hub which carries a number of the helical impeller blades held in position thereto and defining a plurality of blade channels for the liquid being handled to pass.