Recently, the regulation to the air pollution is required from a viewpoint of environmental issue. The exhaust gas from the diesel engine is one of the factor that the air pollution is caused. Authors have taken note of PM (Particulate Matter) in exhaust gas and have proposed the combustion system of PM by means of high frequency induction heating. In this paper, as experimental results, it is proved that PM is reduced by PM reduction system utilizing high frequency induction heating. Furthermore, a novel high frequency inverter as the power supply for high frequency induction heating is proposed. And the circuit characteristics are clarified. As a result, although the circuit parameters are changed according to temperature in order to heat a metallic filter to high temperature, this inverter has realized stable operation.

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The study of reducing NOx emission without increasing specific fuel oil consumption was conducted using medium bore size 4-stroke low speed diesel engine. Engine performance simulation was done before engine test. Designed parts owing to the calculation result were evaluated by means of a test on a 6 cylinder engine (bore: 340mm, stroke: 680mm, rated engine speed: 280min^-1) . From these studies, practical technique of reducing NOx emission and specific fuel oil consumption was found, and this improved NOx emission level is within IMO NOx regulation. This paper reports these engineering findings.

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In the conventional system of lubrication, lubricating oil is renewed with fresh oil after it is used for some period. Accordingly, waste oil is generated in the conventional system.The authors have developed a new system that makes it possible to use lubricating oil semi-permanently without oil renewal. In the new system, therefore, no waste oil is generated and it is enough to supply only a small amount of fresh oil sometimes to compensate for the lost oil. The new system always keeps the lubricating oil clean as the kidney of animals always keeps their blood clean. This is why lubricating oil can be used semi-permanently and the new system is called kidney system. This system has been working well in about one thousand units of marine and cogeneration diesel engines in practice. Also, the new LO system improves reliability of engines. Expecting further higher reliability by combining the LO kidney system with an improved FO system, some engine tests were carried out and this paper firstly reports about the remarkably good effect of FO GEL breaker on engine reliability. Secondly, it reports that there were almost no troubles during 8000 hour running of a cogeneration diesel engine which was eguipped with (1) the LO kidney sy stem, (2) the improved FO system and (3) the fire ring to prevent gas blow-by between the piston and the cylinder. Lastly, the paper reports about the good results in some other cogeneration diesel engines eguipped with the LO kidney system.

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