Studies on the Characteristics of Axial-Flow Pumps : Part 1, General Tendencies of the Characteristics of Pumps

Abstract

The essential object of this paper is to know the reasons for the conspicuous increase of the head and brake horse-power of an axial-flow pump at low flow rates. In this report, the characteristics of pump, the flows before and behind the impeller blades and the pressure distributions on the casing wall near the impeller and guide vanes were measured. The results obtained are mainly as follows : 1. When the discharge becomes less than that which begins the reverse flow on the suction side of impeller blades, the radial flow in the impeller increases suddenly, and the characteristics of pump change remarkably, too. 2. At that time, the casing wall gives an important effect upon the radial flow in the impeller and the angle between the rotational direction and the relative velocity of the fluid becomes larger than the discharge angle of runner blades near the casing on the delivery side of the impeller.