On suppressing cavitation surge by using tandem bladed helical inducer with low solidity front blades

A cavitation surge oscillation in the range of partial flow rate and low NPSH hinders the wide operation of an inducer for industrial turbo-pumps, though it is very effective to improve the cavitation performance. The harmful oscillation of cavitation surge occurs in the case of inducers with high solidity more than 1.0. This oscillation might be suppressed if a tandem bladed inducer, having a front inducer with low solidity less than 1.0, would be employed. Experiment tests to examine its effect are described in the present paper. Results show that the amplitude of the oscillation takes almost zero when a relative peripheral or axial position between the front and rear blades is properly chosen. The reasons are discussed with measured casing wall pressure distributions and observed cavitation behaviors.