In order to meet the IMO NOx TierIII regulations which took effect in 2016, NOx emissions from ships operating in emission control areas (ECA) need to decrease by 80% from the IMO NOx TierⅠlevel. EGR and SCR technologies are believed to be highly effective in satisfying the TierIII requirements. However, according to data obtained with the use of MAN Diesel & Turbo’s Computerized Engine Application System (CEAS), SCR techniques are more fuel efficient than EGR technologies. Especially, the marine SCR system developed by Hitachi Zosen Corporation offers strong fuel economy in that the system can raise the SCR operating temperature above the level required for denitration reaction with exhaust gas energy only. This paper outlines SCR systems and explains the influence of SCR operations on engine performance and fuel oil consumption in a large two-stroke engine 6S46MC-C7 fitted with our High Pressure SCR (HP-SCR).
To comply with the IMO Tier III regulations, Japan Engine Corporation (J-ENG) has developed a new and unique exhaust emission reduction technology “Low Pressure Exhaust Gas Recirculation (LP-EGR) system”. J-ENG’s LP-EGR system is a system which generation of NOx is suppressed by changing combustion condition inside an engine, by means of recirculating a part of low pressure exhaust gas emitted from an engine turbocharger outlet to a turbocharger intake after scrubbed by the EGR scrubber. Now, we have applied integrated on-engine LP-EGR system into a commercial engine 6UEC45LSE-Eco-B2 aiming for onboard durability confirmation. As a result of its shop test, we confirmed its NOx emission amount complied with the IMO Tier III regulations in witness whereof the ClassNK and that the increase of fuel oil consumption was less than approximately 1%. After installing the system onto a 34,000DWT Bulk Carrier, we are now conducting a long-term durability confirmation during commercial voyages. Since J-ENG’s LP-EGR system utilizes low pressure exhaust gas as the EGR gas, it is easy installed on any type of engines and for this reason, we are confident that it will spread widely in the near future.
Seaborne transportation of hydrogen fuel cell vehicles (HFCVs) by pure car carriers is highly expected to increase due to rising demand for environmental protection in the world. When hydrogen leaks from a HFCV, it may accumulate near the ceiling of a vehicle space, since stiffening members referred to as longitudinal girder, web beams and longitudinal frames act as so-called “smoke barriers”. When carrying out safety assessment of the carriage of HFCVs with possible hydrogen leakage, it is necessary to validate numerical simulation tools to accurately predict ventilation flow properties and hydrogen behavior near the ceiling of a vehicle space. For this purpose, large-eddy simulation (LES) on ventilation flow and hydrogen dispersion in a wind tunnel has been carried out using Fire Dynamics Simulator (FDS), which is one of the well-validated computational fluid dynamics (CFD) codes. The sensitivities of computational grid size and subgrid-scale (SGS) models in the LES technique have been investigated by comparing measurement data. The results indicated that when ventilating the wind tunnel without releasing hydrogen, the present CFD calculations could reproduce the measurement data on velocity profiles without dependence on the SGS models by assigning more than about 10 computational grids to the “smoke barriers” in the depth direction. On the other hand, in the case of ventilation with releasing hydrogen, numerical results with the same grid size considerably underestimated experimental data on hydrogen concentrations. Therefore, care should be taken for the interpretation of real-scale simulation results with relatively coarse, computational grids. The present numerical results also point to a need to improve SGS models in such a way that the effects of stratification of hydrogen/air mixture due to buoyancy can be taken into consideration.
The purpose of this study is the generation of alkali and acidic seawater for improving the performance of a scrubber and the sterilization of ballast water by 2-room electrolysis. The experiment was carried out using 1-room and 2-room types of electrolysis. The volume ratio between the anode and cathode tanks was changed. Alkalinity, HClO concentration and survival ratio were measured. As a result, the HClO ratio was 45% in the 1-room electrolysis, whereas the HClO ratio in the cathode tank of the 2-room electrolysis was 80% or higher at any volume ratio. The survival ratio in the anode tank decreased with the volume ratio of this tank. The inactivation effect on halotolerance yeast in the 2-room type was higher than that in the 1-room type. An SEM morphology observation of the yeast after the electrolysis revealed that the cell wall was destroyed by the treatment.
Bolted joints used in rotary machines, such as electric generators, are commonly subjected to high centrifugal forces. When rotary machines are used in a way that repeats running and shut-down conditions, a fair level of stress amplitude occurs in the threaded portions of bolted joints. The magnitude of stress amplitude increases as the rotational speed is increased, which may lead to fatigue failure of the joint. To avoid such fatal accidents and provide effective guidelines for designing rotary machines, it is necessary to clarify the fundamental mechanical behavior of bolted joints under centrifugal forces.
In this paper, using the three-dimensional finite element method and elementary theory of solid mechanics, the mechanical behavior of bolted joints subjected to centrifugal forces is comprehensively studied. In this process, emphasis is placed on the maximum stress amplitude and the rotational speed that causes the complete separation of the interface and lowers the joint strength. It is found that the maximum stress amplitude occurs at the first bolt thread root, and it shows a steep increase when the contact between clamped parts is almost lost. It is also shown that the elementary theory of solid mechanics on compound cylinders can be successfully applied to estimate the aforementioned critical rotational speed.