CFRP プロペラ搭載船の波浪中燃料消費性能に関する基礎的研究

<p>Ship propellers made of Carbon Fiber Reinforced Plastic (CFRP) is expected to be beneficial for the propulsion plant operation in waves. This is because the elastic modulus of the CFRP is lower than that of bronze alloys of a conventional propeller, thus in the condition of varying load in waves, the pitch of the propeller made of the CFRP slightly changes reducing the load fluctuation of a propulsion engine. In response, the engine control system also reduces the correction of fuel amount required to keep the shaft rotation speed constant. In this respect, the engine combustion process takes place in a relatively stable condition favoring better fuel efficiency of the propulsion plant. In this study, the propulsion performance of a ship with the CFRP propeller in waves is investigated experimentally and numerically. The ship's performance with the CFRP propeller is evaluated by comparing it with that of the conventional propeller. The ship with the conventional propeller is designed to correspond to such ship with the CFRP propeller. The propulsion engine characteristics are represented by the Hybrid-CMV model of the diesel engine. This engine model is able to explicitly introduce the fuel-combustion process in the framework of the Cycle-Mean Value approach. A time-series calculation methodology for the ship speed and the engine states in waves is explained in the first place, that is the propeller thrust and torque models in waves are coupled to the Hybrid-CMV engine model. Secondly, the proposed calculation method is validated through experimental results of the free-running model test in regular head waves, using the Marine Diesel Engine Simulator (MDES). The MDES is the self-propulsion device of the propeller model, which utilizes the engine response model. In the model tests, the model of the CFRP propeller, made of chloroethylene-resin which is chosen to correspond the elastic modulus to in full-scale, was taken. The experimental results are also compared with those obtained using the conventional propeller. Thirdly, with the validated calculation methodology, the propulsion performance in waves of the ship with the CFRP propeller is investigated through the numerical speed-trial test in regular head waves. With the focus on the characteristics of fuel consumption, it was confirmed that the CFRP propeller contributes to better engine fuel efficiency when operating in waves.</p>