Study on Actual Performance of Large Tanker Fitted with Ducted Propeller

Abstract

We, Kawasaki H.I., Ltd., successfully delivered on 15th December, 1970 a 215,000 DWT and 30,000 SHP VLCC which was equipped with ducted propeller, first in the world-T.T. GOLAR NICHU. Her operational results are satisfactory. Subsequently we built three sister ships fitted with ducted propeller, and six sister ships with conventional propeller designed on the same lines plan. (These ships are to be referred to as series I.) Furthermore, we completed three 245,000 DWT ore oil carriers, one of which was fitted with ducted propeller (33,000 SHP) and the other two were fitted with conventional propeller. (These ships are to be referred to as series II.) In this report, comparison is made between the ducted propeller ship and the conventional propeller ship in regard to performance based on the operational data of the series I and II ships. The following items are studied and conclusions are obtained. A) Speed Performance 1) Correction is made for the speed trial results, excluding effects of wind and tidal current, and then comparison is made. 2) Considering speed, RPM, HP, wind force, wind direction and sea condition picked up from log book, performances in the condition corresponding to no-wind and calm condition are compared. These comparisons show approximately the same results: Speed gain by installation of ducted propeller is 0.35 knot in full load condition and 0.3 knots in ballast condition, and power reduction at the same speed is 7% in full load condition and 5% in ballast condition. B) Maneuverabillity Analysing results of turning tests, Z-tests and spiral tests, we can find that installation of the duct refines turning ability, but reduces course keeping ability, namely increases unstable loop width by about 2 to 3 degrees (full amplitude), but this has no effect practically. C) Vibration Vibration reduces in full load condition, but increases a little bit in ballast condition when immersion of the duct is small. In addition, we describe, in the report, construction in regard to installation of the duct to the main hull and the accuracy control. From the abovementioned analyses, it could be proved that installation of the ducted propeller on VLCC improves ship's performance.