Investigations on the performance of centrifugal pumps in conjunction with inducers

An inducer is an axial flow impeller with blades that wrap in a helix around a central hub. An inducer serves as a small booster pump for the main impellers. Usually inducers have between 2 and 4 vanes, although they may be more, the inducer imparts sufficient head to the liquid so that the NPSH requirement of the adjacent main impeller is satisfied. Although the inducer usually has a lower NPSH requirement than the main impeller, it can, and often does, cavitate during normal operation, the key is that there is so little horse power involved with an inducer that there is virtually no noise, vibration, or resulting mechanical problems. An inducer invariably has higher suction specific speed (S) than an adjacent impeller (S) is a dimensionless term that describes the inlet characteristics of a pump.