Reduction of Propeller Cavitation Noise by PBCF (Propeller Boss Cap Fins)

Abstract

PBCF (Propeller Boss Cap Fins) which is composed of small fins attached to propeller boss cap was proposed as a novel energy-saving device, and propeller efficiency gain by PBCF has been confirmed through many kinds of model tests and actual sea trials. Currently more than 100 PBCFs are attached to full scale propellers and also demonstrating the effect of eaergy saving. This paper describes the study on cavitation pattern of propeller with PBCF and the effect of PBCF on the noise generated by propeller through the model experiment in cavitation tunnel. The results obtained were as follows; (1) PBCF extinguishes hub vortex cavitation thoroughly but hardly influences on the cavitation generated on blades or tip vortex cavitation. (2) PBCF reduces 3 to 6 dB of sound pressure level of propeller in the range of over 25KHz in the experiment. These results lead us to believe that PBCF is also effective on reduction of propeller noise.