Vane pump

Claim 1

A vane pump comprising a convergent housing which accommodates an axial-flow suction wheel and a main axial-flow wheel installed in said housing, said suction wheel having a varying radial clearance with said housing, and said wheels mounted one after the other in the direction of flow on a common drive shaft, said suction wheel having a hub with helical vanes attached thereto that increase in pitch in the direction of flow, characterized in that the inside diameter of the pump in the inlet section of the axial-flow suction wheel has a diameter that decreases in the direction of flow from a maximum value to a minimum value at the inlet section of the main axial-flow wheel and equal to the inlet diameter of the main axial-flow wheel, the radial clearance between the housing and the axial-flow suction wheel being maximum at the inlet thereof and diminishing along the suction wheel to a minimum value substantially equal to zero at the inlet section of the main axial-flow wheel, the maximum value of the inside diameter (D o ) of the pump housing being chosen according to: D.sub.o =D.sub.1 ·K.sub.1 (C.sub.k ·10.sup.-4 +2.1).sup.2, where D o --inside diameter of the pump housing at the inlet section of the suction wheel; D 1 --inside diameter of the pump housing at the inlet section of the main axial-flow wheel; K 1 --dimensionless coefficient of 0.17 to 0.13 C k --predetermined cavitation critical speed coefficient to 5,000 to 11,000; and the setting angle (β o ) of the tip of the vane in the inlet section of the axial-flow suction wheel is minimal and determined according to: β.sub.o =(10=33Δ/D.sub.1)°+1.50, where β 0 --setting angle of the tip of the vane in the inlet section of the axial-flow suction wheel; Δ--radial clearance in the inlet section of the axial-flow suction wheel; D 1 --inside diameter of the pump housing in the inlet section of the impeller wheel.