To comply with the IMO NOx Tier III regulations, we have developed a new and unique technology called “Low Pressure Exhaust Gas Recirculation (LP-EGR) system”. The LP-EGR system is a system which recirculates a part of low pressure exhaust gas emitted from an engine turbocharger outlet into a turbocharger intake after scrubbed by an EGR scrubber. We applied the integrated on-engine LP-EGR system into a commercial engine 6UEC45LSE-Eco-B2 aiming for onboard durability confirmation. The results showed that its NOx emission level was within the IMO Tier III regulations and that the increase of fuel oil consumption was approximately less than 1%. This was the first time in the world that the LP- EGR system installed into a marine low speed two-stroke diesel engine has satisfied the IMO NOx Tier III regulations.
Furthermore, we installed the system into a 34,000DWT bulk carrier, and we are currently checking its long-term durability through sea trial and commercial voyages. Now, the system has archieved about 400 running hours in total during commercial voyages. This was also the first effort that the LP-EGR system, which complies with the IMO NOx Tier III regulations, was installed into a marine low speed two-stroke diesel engine of a vessel that is actually operating at sea.
This work is designed to collect components of particulate matter (PM) emitted from two medium speed 4-stroke marine diesel engines and a low speed 2-stroke marine diesel engine and to use these emissions as an inventory of air pollutants for air quality simulation. The sulfur content of the fuels used in the experiment ranged from 0.071% to 2.49%. The PM sample was examined with two partial flow dilution systems in accordance with JIS B 8008-1: 2000. The components of nitrate and sulfate in PM were analyzed by ion chromatography. The components of organic carbon and elemental carbon in PM were analyzed by the thermal-optical reflectance method (protocol: IMPROVE). The results were examined in terms of component (five classifications - nitrate, sulfate, organic carbon, elemental carbon and others) and points to note for the creation of the inventory were prepared.
Various PMs are emitted from marine diesel exhaust gas. Since re-entrainment phenomena occur in the conventional ESP, the hole-type ESP was newly developed to overcome re-entrainment in ESPs. The hole-type ESP utilizes the ionic wind, which is generated by a corona discharge. The ionic wind guides particles into the hole. The electric field of a collecting zone in the hole is zero, meaning that re-entrainment may be expected to be suppressed. In our studies, the upstream and downstream particle concentrations were measured to determine their collection efficiency. The highest collection efficiency for small particles was achieved with 22.6% of the aperture rate. In the conventional ESP, a re-entrainment phenomenon occurred when the primary flow velocity increased. However, re-entrainment was suppressed in the hole-type ESP under the same conditions.
Surface texturing is one of the approaches for the application of sliding contact elements. It is widely used to improve load capacity and tribological performance of mechanical components. In addition, it is known that surface texturing is effective in collecting wear debris and the running-in of sliding surfaces. The lubrication characteristics on sliding surfaces may vary depending on the shape, size and pattern of surface texturing, but how much these elements can affect the characteristics have not been fully understood. In this study, authors conducted a numerical analysis of the solution of Reynolds equation using a finite element method, which can assess the effect of surface texturing on film formation by hydrodynamic lubrication. The results showed that in general, oil film pressure decreased at the entrance portion of surface texturing and increased rapidly at the exit portion. In case of several surface texturing machined, variation of oil film pressure repeats at the position of surface texturing. Since oil film pressure varied based mainly on the location of textured surfaces, it is possible to decrease the maximum pressure by changing their locations. Authors found that the lubrication characteristics were not affected very much by the shape of textured surfaces, but largely influenced by their locations. Through various approaches, the lubrication characteristics were improved by focusing an analysis on the outlet side of textured surfaces instead of conducting an analysis in the whole area as the former makes the force of friction smaller.
Our research team applied surface modification processes to alloy steel to improve its corrosion and wear resistance, especially in seawater. The processes included fine powder intrusion, post processing, carburizing and zinc coating. Two different kinds of powder, Cr and Mo, were used for powder intrusion. After the modification, corrosion and friction tests were conducted on the specimens. The results showed that the modified materials demonstrated excellent wear resistance and anti-corrosion properties.
Hybrid propulsion systems are attracting more attention as a way to save fuel. In an attempt to apply this system that does not have a large battery capacity to a tugboat, the authors have studied the correlation between its control method and efficiency on the condition that the tugboat was not in service. Data is calculated by using a simulation model that the authors had developed. When it comes to hybrid propulsion system, it is important to control size and direction of energy. Three control patterns were presented and evaluated in a comprehensive way taking controllability, redundancy, and efficiency of the entire system into consideration. The simulation results highlighted the main characteristics of the control patterns. They also made it clear that decreasing energy loss in a slipping clutch contributes to improving hybrid propulsion system efficiency.
This study experimentally investigated heat transfer and pressure drop on condensation and evaporation flows of R410A inside horizontal aluminum microfin tubes at saturation temperatures of 35°C and 10°C for condensation and evaporation flows, respectively. The test microfin tubes had an outer diameter of 8 mm, helix angles of 0 and 20 degree, 36 fins, and fin heights of 0.3 mm. The effects of mass velocity, quality, and helix angle on the heat transfer and pressure drop characteristics for condensation and evaporation flows were investigated. Furthermore, the effect of heat flux on evaporation heat transfer coefficient was also investigated. The measured heat transfer coefficient and pressure drop on the condensation and evaporation flows were compared with the several previous correlations. The correlation of pressure drop for condensation and boiling flows was developed based on present data. The proposed correlation successfully predicted the experimental frictional pressure drop for condensation and boiling flows inside aluminum microfin tubes.