The increasing rate of engine sound and vibration is a grave problem on the coastal fishing boats. The acoustic characteristics of sound emission were studied with respect to the cetane Indices of fuel using a single cylinder diesel engine. At the same time, NOx emission was evaluated to cetane index correlation. Consequently, levels of combustion sound and NOx emission were increased appreciably at cetane Indexs below 45. These are due largely to the high rate of combustion pressure rise just when the violent pre-mixed combustion caused by long ignition delay occurred.

View full abstract

The purposes of this sutdy are to clarify the characteristics of cavitation erosion in piping line behind a butterfly valve and to propose the method of predicting the erosion resistance.
One of the major obstructions in an experiment of cavitation erosion is taking a long time with the use of metal specimen. Therefore, the use of a substitutive material which had the fragile property to anti-cavitation erosion was proposed in this study and the similarity of the erosion characteristics was confirmed between the substitutive material and the real material.
In the second stage of this study, the substitutive material was installed as pipe wall at a bend behind a butterfly valve. It was confirmed from observations and measuring the position of erosion that the erosion of the material was due to cavitation occured at the butterfly valve. Therefore the prediction of the erosion resistance in a real condition is possible from the result of the similarities of erosion characteristics of a substitutive material.

View full abstract

The mechanism of soot-fire accident of exhaust gas economizer in diesel ship is investigated in this report. This is the second report following the first one, in which the process of soot-burning of exhaust gas economizer was studied by a simulation model. According to the soot-burning simulation, temperature of heat transfer surface seldom reaches its melting point only by soot-burning. So it is difficult to consider that soot-fire is occurred only by heat released by the soot-burning. It has been reported the oxidative heat of tube materials might be another heat source. The experiments, therefore, are carried out in order to measure the rate of oxidation of tube materials, and reveal that there is a possibility that the oxidative heat might be another heat source when the oxidation rate is accelerated by the high temperature steam atmosphere and the“break-away”oxidation. Accordingly it is made clear the soot-fire is occurred by a series of events, that is, burning of soots deposited on finned tubes, waterside dry-out of the finned tubes induced by the soot-burning, sudden degradation of waterside heat removal due to the dry-out, rapid increase of fin temperature, and further increase of the fin temperature due to oxidation of iron, and finally melt-down of the heat transfer surfaces.

View full abstract

This paper describes the information of the engine modification for reducing NOx discharge from the diesel engine. The authors performed combustion tests on single-cylinder engine with 165mm in bore modified only elements of combustion-related systems.It was found that an appropriate combination of factors of the piston bowl and the fuel injection system could improve NOx emission by about 30% at higher loads without major increase in fuel consumption and exhaust smoke.

View full abstract