An experimental study was carried out in order to clarify combustion characteristics of low grade future fuels. The tested fuels were some conventional fuels and those produced by the thermal and the catalytic cracking. The experiment was made on a high, a medium and a low speed marine diesel engine.
The main results obtained are (1) ignition lag increases with content of aromatics in the range over about 30%, (2) the exhaust gas temperature increases with content of aromatics while temperature of combustion chamber components increases with asphaltenes, (3) wear of piston rings increases with aromatics and (4) the Alumina Gel Chromatography is a recommendable method to determine content of aromatics in the case of heavy fuel oils.

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In order to understand a diesel combustion, it is necessary to pay attention to an air motion and a fuel spray pattern in a combustion chamber, which exert a serious influence upon the diesel combustion, then we examined the relation between engine performances and them.
An extensive series of tests has been carried out on a steady state flow rig about characteristics of intake and exhaust ports, and the air motions in the chamber were examined from the results. The fuel spray pattern in a constant volume model chamber has been observed by a high speed camera.
Moreover we tried to predict the engine performance from the air motion and the fuel spray pattern by a simulation program, and the comparisons were made between predicted and measured fuel consumptions and smokes on variables (fuel nozzle specification, shape of combustion chamber and characteristics of the ports) . And the results show that we might be able to predict the fuel consumption and smoke trends on the variables.

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Recently, the improvement of fuel economy and the reduction of exhaust smoke and NO have been successfully achieved by supplying diesel engines with emulsified diesel oil with water particles.
In the present paper, the difference between the combustion of injected emulsion and that of diesel oil spray is clarified by means of taking high-speed and color photographs of the flames in engine cylinder and in hot air stream. As the results, the two kinds of fuels show different combustion behaviour each other in the growth of initial flame and in the termination of overall combustion in the cylinder. Then, suitable combustion chamber design for the use of emulsified fuel is discussed on the basis of experimental data for various distributions of spray in various kinds of piston cavities. Some methods of clearing troubles caused by emulsified fuel are also discussed on the basis of performance data on a practical high-speed open-chamber diesel engine.

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It is presented a method to estimate dynamic characteristics of ac-dc electric propulsion system for designing to meet given specifications. The system of model ship is composed of each one element such as a main diesel engine, ac generator, rectifier circuit and do propulsion motor.
Simulation techniques on both thyristor Leonard and diode-Leonard system are introduced. It is also discussed on ideas to control each Leonard system.
Numerical results interested in crush astern operation at running harbor-full speed, are calculated on both cases of diode and thyristor Leonard system. Controllabilities of both systems on the model ship, since making a straight drive, have little difference with regard to transient vessel speed and distance to stop.

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