Multi-Purpose Ducted CP-Propellers for a Semi-Submersible Offshore Support Vessel

摘要

A semi-submersible support vessel consisting of a platform connected by columns to two displacing pontoons was designed with two main fixed shaft CP propellers in partially steering ducts. These propulsion units had to fulfill certain requirements at different draughts and propeller loadings, which entailed a difficult compromise design. The main problem was the reconcilation of the conflicting requirements for almost equal ahead and astern bollard pull thrust in the operating (deep draught) condition, with cavitation free operation at full speed in the transit (light draught) condition. In this paper three different propeller designs which were investigated are described. The results of the model tests which were carried out in the SSPA cavitation laboratory and in the towing tank have been analysed and are discussed.