Diesel engines have been used in various fields because of their high thermal efficiency and application of low grade fuels. However it now becomes a great problem that their exhaust particles, i.e. soot, have considerable influence on environmental pollution.
The process and mechanism of soot formation in diesel combustion have not necessarily been explained. The authors made an attempt to make clear the process of soot formation in a combustion chamber by optical means. The measuring method was conducted from the Lambert-Beer's law combined with the Mie's light scattering theory. It stands on the principle that extinction of light beam through particles, for instance soot in combustion chamber, is dependent on the wavelength and diameters of the particles. This multi-wavelength light extinction technique was proved to be practical by the measurement of polystyrene particles which were usually used as calibration aid in electron microphotography. Furthermore, it was applied to propane-air diffusion flames, and reasonable values of the volumetric density and the particle size distribution were obtained without difficulty. The authors confirm that the method is helpful to the combustion analysis because of its simple procedure and readiness for application.

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In relation to the remarkable effect of emulsified diesel oil with water particles on reducing exhaust pollutants (NO_x, soot etc.) and also specific fuel consumption of the diesel engines, the micro-explosion phenomena in the flame of a heated fuel droplet on a silica filament in a high pressure chamber investigated experimentally.
The experimental results are summarized as follows:
With the increase of the initial air pressure in the chamber,
(1) The micro-explosion likely becomes weaker, so that the projected flame area on the motion picture of 8-mm wide gets smaller.
(2) The difference between the flame shape of the emulsion and that of diesel oil gets less.
(3) The burning time of an emulsified fuel droplet increases approaching that of diesel oil droplet.
As a result, the authors appraise the effect of the micro-explosion on reducing specific fuel consumption and exhaust smoke of a diesel engine to be small because of the high pressure in the engine cylinder.

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Propeller loads fluctuate in various route environment such as crushing submerged or floating objects, or air ventilation. The electric propulsion system can alter the torque/speed characteristics of a diesel engine to meet any forced load, required response time and continuation of ship's controllability.
Authors have reported a method for calculating dynamic characteristics of the electric propulsion system. Proposed technique utilize both control circuit and power system analysis for synthesizing a propulsion system to meet given performance requirements.
Analytical waveforms of propeller loads are supposed rectangular, caused by correlative motion of ship's pitching and sea waves resulted in air ventilation.
Constant speed control system is established on static Leonard system, which contains current limit circuit and buffer circuit to suppress higher current fluctuation proposed in this paper.
Numerical responses with rectangular loading to propeller on the model ship are presented and are also compared to those of the diesel propulsion system to estimate influences on combustion of main diesel engine.

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As petroleum refining techniques have developed, the quality of marine fuels has been declining. This has posed increasing difficulties in the treatment of fuel oil for diesel engines.
In these circumstances, the fuel oil reformer, which uses ultrasonic technology, has several advantages, its principal advantage is that the ultra-sonic energy disperses the sludge suspended in the lower grade heavy fuel into superfine particles. This improves combustion in the diesel engine.
This paper gives a comprehensive description of the structure and characteristics of the Fuel Oil Reformer. Results of actual operation of an auxiliary diesel engine with this equipment using heavy fuel oil is also discussed. Tests were conducted on the high seas.

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