抄録
The attachment of inducer in front of main impeller is a powerful method to improve cavitation performance. In operating condition at partial flow rate and extremely low suction pressure, however, cavitation surge oscillation occurs. As the cavitation surge oscillation with low frequency occurs in a close relation between the inlet back-flow cavitation and the growth of blade cavity into the throat section of blade passage, one method of installing an axi-asymmetrical plate upstream of inducer has been proposed to suppress the oscillation. The inlet flow distortion due to the axi-asymmetrical plate makes different elongation of cavity on all blades, which prevents the flow from becoming simultaneously unstable at all throat sections. In the present study, changes of the suppression effects with the axial distance between the inducer inlet and the plate and the changes with the blockage ratios of plate area to the cross-sectional area of inducer inlet are investigated for helical inducers with tip blade angles of 8° and 14°.Then a conceivable application will be proposed to suppress the cavitation surge oscillation by installing axi-asymmetrical inlet plate.
