Abstract
With respect to the impeller with radial blades and inducer blades revised in the inlet geometry, the flow visualization of the separation ring on the shroud casing wall was conducted as well as a 3-D steady turbulent flow calculation in order to investigate the inducer stall at small flow rates. The numerical analysis shows that the small separation bubble appears at the blade root leading on the blade suction side at small flow rates, then, the reverse flow appears and develops remarkably at the inducer tip portion as the flow rate decreases further. Judging from these results, the initial unstable flow might be caused by the separation at the blade leading, and the strong unstable flow might be due to the large reverse flow at the inducer tip portion.
