A Study on Correlation between Propeller Pitch Distribution and Improvement of Propeller Efficiency by PBCF

Abstract

PBCF (Propeller Boss Cap Fins) is a boss cap with small fins. It recovers the rotational energy in propeller slipstresm by eliminating the hub vortex and improves propeller efficiency. In this paper it was studied how propeller efficiency with PBCF changes by changing pitch distribution of a propeller. Three model propellers, what are called increasing pitch propeller, constant pitch propeller and decreasing pitch propeller respectively, were made changing pitch ratio of each root part. And those were tested in uniform flow and two different non-uniform flows with or without PBCF. On the other hand calculation of propeller performance has made. The results obtained are ; (1) Significant efficiency improvement by PBCF has obtained for all the propellers, and it was 2〜8% in this model test. (2) Increasing pitch propeller, which seems to be adapted to the wake, has also been improved by PBCF. (3) It may be possible that a more efficient propeller is designed considering PBCF and well-matched propeller pitch distribution.