Performance and internal flow characteristics of a very low specific speed centrifugal pump

In very low specific speed range (n(s)< 0.25), the efficiency of the centrifugal pump designed by the conventional method becomes remarkably low. Therefore, positive-displacement pumps have been widely, used for long. However the positive-displacement pumps remain associated with problems such as noise and vibration and they require high manufacturing precision. Since the recently used centrifugal pumps art becoming higher in rotational speed and smaller in size, there appear to be many expectations to dcvelop a new centrifugal pump, with high performance in the very low specific speed range. The purpose of this study is to investigate the internal flow, characteristics and its influence on the performance of a very/low specific speed centrifugal pump. The results show that large reverse flow at the send-open impeller outlet decreases absolute tangential velocity considerably which in turn decreases the pumping head.