Study on Economical Ship Speeds (2nd Report)

Abstract

The effects of two propeller types and various main engine rates on the propulsive performance of a ship in waves, are investigated in consideration of economical ship speeds and minimum fuel oil consumption in waves. A 86,000 DWT bulk carrier on a Japan&#8764;North America route was chosen for the investigation. The load condition of the ship is a full load and the encounter angle between the ship and irregular waves is assumed to be head-on. Sea states which may occur during a voyage are estimated by using the long term wave frequency data. The results of the theoretical calculations show that the minimum fuel oil consumption of the ship when equiped with a CPP is 6% lower in the winter and 2% lower for a one year period than that of the ship when equiped with a FPP. Furthermore it is shown that the minimum fuel oil consumption of the ship equiped with a CPP is 5% lower, even for a one year period, than that of a FPP in the case that the frictional resistance coefficient is increased by 1×10^<-3> due to the fouling of the hull surface. Finally, it is shown in the case of the ship equiped with a CPP that the minimum fuel oil consumption of the ship when equiped with a main engine of MCR=12,000ps is about 5% higher than that of the ship when equiped with a main engine of MCR=14,200ps.