A Study on the Improvement of Performance of the Axial-Flow Pump

抄録

The axial-flow pump was examined from the point of view of cavitation characteristics. The studies clarified the relationship between specific speed N_s and impeller diameters. According to this relationship, the suction performance of the axial-flow pump was expected to be improved by making its inlet diameter smaller than that of the outlet. Impellers of axial- and mixed-flow types, of the same design point and the same mean outlet diameter, were tested to prove the above supposition. The experiments revealed the following : in pump performance the mixed-flow impeller showed higher efficiency by 1 to 2% at normal flow and by about 5% at partial flow, and the shut-off horsepower decreased in proportion to the square of inlet diameter in the case where the mean outlet diameter was kept the same. In suction performance the mixed-flow impeller was superior in the incipience, except for K₁ cavitation, and showed about 10 to 20% higher critical S-values for drop in head and efficiency as compared with the axial-flow.