In discharge of bilge from a ship's engine room to the sea, the oil content of the effluent shall not exceed 15 parts per million. To improve the performance of oily water separators, we analyzed bilge water characteristics then fabricated a prototype filtration unit and evaluated its performance. Test samples were collected from actually operating ships and compared with the test liquid stipulated by the IMO. Some proposals are presented for processing oily water in the ship's engine room.
Gas engines are increasingly coming into use in Japan as cogeneration engines. In some cases, the lubricating oil of such engines is replaced very often because it turns black in a short time. The authors, therefore, conducted experiments to obtain information on overcoming the rapid blackening. The results show that the black lubricating oil in gas engines may be caused by the high temperatures of these engines. It therefore may not be difficult to cope with the problem.
The safety of ship valves requires confirmation only by pressure shell tests, but ship-mounted valves are subject not only to pressure but to various forces applied through pipes during ship construction and operation. We therefore investigated the safety of type 5K-80A valves by experiments and numerical analyses. The results may be summarized as follows: (1) The vertical force that can cause leakage from the valve seat is less that the corresponding horizontal force, but the critical value of vertical force is much smaller than the force exerted on an actual valve. (2) The pressure test showed a safety factor of 21.6, which is far greater than the factor of 8 required by the design standard. (3) Operating torque increases, rather than decreases, the safety of a marine globe valve.
Steady-state and transient boiling heat transfer characteristics for highly wetting liquid due to an exponentially increasing heat input with time have been investigated. It is important to make the best of existing energy conversion technology for the utilization of boiling heat transfer. Steady-state and transient critical heat fluxes (CHFs) were measured by using a 1.0 mm-diameter horizontal cylinder in a pool of water and highly wetting liquid such as ethanol with a period ranging from about 10 ms to 20s for wide ranges of subcooling and pressure. The transient CHFs depending on the periods were divided into two principal groups: the first one was in long period and the CHF occurred with fully developed nucleate boiling heat transfer processes, and the second one was in short period with explosive boiling heat transfer processes from non-boiling and the direct transition to film boiling occurred. The CHFs increase with an increase in subcooling at pressures and they are independent of pressures at high subcoolings. A large part of the transition processes to film boiling at CHFs for highly subcooled liquid measured can not be explained by the mechanism based on the conventional hydrodynamic instability (HI) model. However, the transition processes to film boiling at high subcooling can be explained by the heterogeneous spontaneous nucleation (HSN) model suggested by Sakurai et al.. In the HSN model, it is assumed that the transition occurs due to the explosive boiling in originally flooded cavities on the solid surface in liquid. The measured transition processes to film boiling at CHFs for wide ranges of subcooling and pressure in the test liquids with steady and transient conditions were reasonably explained by the HI and HSN models.
Thermal energy conversion systems for ships on the environment in ocean are commonly limited by the space or equipment. It is very important to make more effective use of the energy systems such as heat exchangers. For the purpose of the improvement of performance for these energy systems, the utilization of boiling heat transfer is the most effective method to solve these kinds of problems. In this research, steady-state and transient subcooled pool boiling heat transfer was carried out using exponentially increasing heat inputs to a horizontal cylinder in a wetting liquid of ethanol. The photographic observations on the vapor behavior at the boiling heat transfer processes were performed using a high-speed video camera.
In marine diesel engines, NOx in exhaust gas emissions is regulated by the IMO (International Maritime Organization) . EGR (exhaust gas recirculation) is widely used for NOx reduction, but EGR aggravates fuel consumption. Research on intake and exhaust valve timing is necessary to make active use of internal EGR without increasing BSFC. In this study, internal EGR was effected by a variable valve timing mechanism using the hydraulic actuator. The NOx reduction consequences were investigated by two methods: an overlap change and late closure of the exhaust valve. The results demonstrated that the negative overlap and late closure of the exhaust valve, using the effect of the other cylinder, have a NOx reduction effect. Because the trade-off between NOx emission and BSFC is maintained with the same exhaust valve opening timing (EO), compatibility between NOx reduction and constant BSFC can be achieved by internal EGR and the delay in EO.