The present paper reports on the development of a new technique of marine bacteria sterilization of ship ballast water using underwater shock waves. The interactions between microbubbles and shock waves are utilized in the proposed technique. The contraction and expansion motion of microbubbles provide biochemical and mechanical sterilization effects by means of free radicals and shock wave pressures. Theoretical and experimental approaches to the development of the present technique are described. The examination of optimum conditions for higher rebound-pressure generation from microbubbles, the observation and pressure measurements in the interaction field between microbubbles and shock waves, the performance of a unique shock wave generator and the bio-experiments with the present technique are featured in this paper.
For drastic reduction of energy necessary to thermal treatment of ballast water, a heat retrieving type ballast-water treatment system (BWTS), Thermal Aqua-Filtration (TAF) system, has been under development. The land-based plant (15 m3/h for TOR), consisting mainly of a plate-type heat exchanger (HX) and a Thermal-treatment Tank with electric heaters for sub-heating, showed to meet D-2 regulation with 70 °C and 5 minutes treatment. By using the land-based plant (15 m3/h for TOR), consisting mainly of a plate-type heat exchanger and a Thermal-treatment Tank with electric heaters for sub-heating, it was confirmed that 70 °C and 5 minutes treatment meet D-2 regulation. The heat-retrieving ratio became over 95 %, which reduces the operation cost of an ocean friendly BWTS to the realistic level. The bio-fouling on the plates of heat exchanger, which has been one of the key technical issues, could well be overcome.
In this paper, problems created by the discharge of ship ballast water and the worldwide movement to address these problems are presented, and various methods of ballast water treatment are introduced. The treatment principle and an application example of JFE BallastAce®, which consists of a filter, an active substance and Venturi tubes, as well as injection control of active substance are described. The methods and results of both land based tests and onboard tests, which are required to gain the type approval, are introduced. A brief introduction of the first commercial application of JFE BallastAce® is also presented. Above stated series of test results confirm that JFE BallastAce® completely satisfies D2 discharge regulation3).
In order to investigate the mechanism in which particulate matter (PM) is discharged from diesel engines, it is necessary to carry out a quantitative analysis of the substances it contains. Paying attention to the calcium content in the PM of a laboratory diesel engine, this research discussed the method of the quantitative analysis conducted, and the mechanism in which it was discharged. The origin of the calcium in PM comes from calcium contained in the lubricating oil of the engine. The calcium in the lubricating oil and in the residual substance of the oil during the evaporation process can be extracted by ultrasonic cleaning with the mobile phase (dilute sulfuric acid) using ion-chromatography. Quantitative analysis of calcium was carried out using ion-chromatography. The same method is used for the quantitative analysis of calcium in dust (JIS Z 8808). The results showed a 0.2 mg/m3N-dry calcium concentration in the exhaust gas of the engine. The rate of lubricating oil consumption was determined to be 0.2 g/kWh from these results. When the lubricating oil is simply heated, the calcium it contains remains the residual substance. Therefore, calcium in the exhaust gas of the engine indicates that a part of the lubricating oil is consumed as oil droplets.
In recent years, sliding performances of mechanical elements have progressed by using coated films which possess superior tribological properties. This has led to the reduction of mechanical element failures. Coated films are often used under severe conditions such as elastohydrodynamic lubrication (EHL). In this paper, in order to devise design guidelines with broad applications for a coated film with interlayer, stress distributions of the coated film, interlayer, and substrate over a wide range of Young’s modulus values for a point contact under EHL conditions were numerically investigated in detail using a three-dimensional analysis method. The results suggest that when the thinner coated films are used, it is preferable that the Young’s modulus of the interlayer ranges from that of the coated film to that of the substrate. In addition, it is desirable to have an interlayer which is not too thick when the Young’s modulus of coated films are smaller than that of substrate, and that the interlayer have larger values of thickness when the Young’s modulus of coated films are larger than that of substrate. On the other hand, when the thicker coated films are used, it is preferable that the interlayer have a certain amount of thickness. Furthermore, when the Young’s modulus of the coated film is larger than that of substrate, it is preferable that the Young’s modulus of the interlayer is larger than that of the substrate.
Urea SCR (Selective Catalytic Reduction) is a promising technique to reduce NOx emissions from diesel engines. In order to apply Urea SCR with high NOx reduction efficiencies, it is necessary to supply the reductant to the exhaust gas for it to be uniformly distributed over the cross section of the exhaust pipe. In addition, it is desirable that the supplied reductant be converted into NH3 as much as possible within the distance between the injection nozzle of the reductant and the inlet of catalyst. In line with these considerations, the present study investigated how spray characteristics influence the spray distribution in space and the evaporation and the thermolysis process of urea water droplet. A simplified 2-D spray model considering droplet size, injection angle, droplet size distribution and flow distribution was proposed. Calculation results revealed that spraying the reductant with smaller sized droplets could be effective in promoting the quick conversion of urea-water solution into NH3. Moreover, it was found that a hollow cone spray whose droplet size distribution had a flat shape could lead to high uniformity of the reductant over the cross section of the exhaust pipe.