A DESIGN METHOD OF THE DUCTED PROPELLER FOR LARGE SHIPS

This paper presents a practical design method of the ducted for large ships, which was developed based on the research results of the ducted for the 280000 DWT tanker Thorsaga. The ducted propeller was developed to provide high performance for large ships with respect to efficiency, cavitation and impeller strength. In analyzing the self-propulsion test results the duct/impeller system is treated as a propulsor, and the method of analysis to take only impeller as the propulsor is also adopted in a supplementary manner, since this method was found to be quite useful in determining the particulars. In order to realize a reliable design by utilizing these two methods of analysis, two kinds of design charts, one for AU-Da ducted series and the other for AU-Da Impeller series, were developed by conducting the systematic open test series. In addition, the procedure of impeller design from cavitation aspect, the method of estimating the self-propulsion factors in early design stage are also given in this design method as well as the model-ship correlation to allow prediction of full scale performance, and thus a practical design system of the ducted for large ships is presented.