Smart Control of Axial Flow Pump Performance by Means of Counter-Rotation

Abstract

Turbo pumps have weak points, such as the pumping operation becoming unstable in the rising portion of the head characteristics and/or the cavitation occurring under the intolerably low suction head. These points have been individually overcome in general, since such phenomena originate in essentially different causes. To overcome the above weak points simultaneously, however, we propose a unique pumping system with counter-rotating mechanism and discuss its advantages. This system consists of two-stage impellers and a unique motor with double rotors. The front and rear impellers are driven respectively by the inner and outer rotors of the motor, keeping the relative rotational speed constant and counter-balancing the rotational torque. Such driving conditions not only improve smartly the unstable performance at low discharge but also suppress smartly cavitation at high discharge, under the optimum cooperation with the impeller works and the rotor outputs. The model test proved that there is no rising portion of the head characteristics and that the front impeller speed is gradually decreased with increase of the discharge as if taking the place of the inducer.