This paper introduces the development of marine diesel engine simulator and proposes a new experimental methodology for self-propulsion test in waves. A marine diesel engine simulator is developed for self-propulsion test of a model ship. This is composed of a servomotor, speed controller, dynamometer and PC. On the PC, marine diesel engine simulation program is installed. Based on a mathematical modeling of the engine, this program simulates fuel supply control by governor, torque generation by combustion and shafting system rotation. Inputs are rotating speed and propeller torque measured by dynamometer, and output is target speed to the speed controller of the servomotor. This is a real-time control system of propeller rotating speed, which reflects the characteristics of marine diesel engine. Using this system, the authors conducted self-propulsion test of a model ship in waves and checked system operation capabilities. We can measure not only ship motion responses but also the realistic dynamic responses of ship propulsion system in waves such as propeller load and rotating speed fluctuation, fuel supply rate and et cetera.
Performance of ships is customarily evaluated in the calm sea even though ships are operated in wind and waves. This is due to the absence of practical technology to guarantee ship performance in the actual sea condition. Accordingly, contractees have no choice to accept the result of sea trial based on this business practice. This situation is hardly improved in these decades. However, to meet the recent requirement of energy saving and CO2 emission reduction, it is craved to develop new technologies to estimate real performance of ships in the actual sea condition. Needless to say, ship performance in calm sea condition, "calm sea performance", is the base of that in actual sea condition, "actual sea performance". Now, let us briefly review the estimation method of the calm sea performance in design stage. Following procedures are commonly used.