Counter-Rotating Type Pump Unit (Rotational Behaviors)

Abstract

Turbo‐pumps have weak points, such as the pumping operation becomes unstable in the rising portion of the head characteristics and/or the cavitation occurs at the low suction head. To overcome simultaneously both weak points, the authors invented the unique pump unit composed of the tandem impellers and the counter‐rotating type motor with the double rotational armatures. The front and the rear impellers are driven by the inner and the outer armatures of the motor, respectively. Both impeller speeds are automatically and smartly adjusted in response to the pumping discharge. Such speeds controlled smartly contribute pretty well to suppress not only the unstable performances at the low discharge but also the cavitation at the high discharge, as verified in the previous paper.Continuously, the effects of the impeller profiles not only on the pump performances but also on the rotational behaviors are discussed in this paper. Two kinds of the blade profile, giving the lower and the higher heads, were prepared as the front and the rear impellers. The pump performances and the both impeller speeds are affected undoubtedly by not only the discharge but also the impeller profiles. The rotational speed of the front impeller is faster than the speed of the rear impeller in the wide discharge, while the tandem impellers composed of the front impeller giving the lower head and the rear impeller giving the higher head. Such behaviors are caused by making the angular momentum change through the front impeller coincide with that through the rear impeller.