Experimental Study on High Efficiency and Highly Reliable Design of Small Sized Pump with Low Specific Speed

摘要

It is well known that centrifugal pump efficiency becomes worse with the decrease of pump size and specific speed. The small-sized pump with low specific speed, in which the impeller outlet velocity was larger than that of regular pumps, was designed by a simple optimum design method combined with blade surface singularity method for decreasing the total loss generated at impeller outlet and in volute casing. Several combinations of centrifugal impeller and volute casing were manufactured and tested for confirming the availability of this design method. The experimental results show as follows: The semi-open impeller with blade outlet angle of 35°, designed by the optimum design method, yielded the highest efficiency of 61% among test impellers in the case of narrow tip clearance. In the case of larger tip clearance, however, the leakage loss becomes dominant for pump efficiency and the efficiency of impeller with blade outlet angle of 60° is higher. This fact implies that the tip clearance should be considered as an additional factor for optimum design