“Cylinder cut” is a well known energy saving technology in the automotive field. This method involves stopping several cylinders of an engine during slow speed operation to decrease “pumping loss”, which refers to the air suction resistance at the throttle valve. The authors applied this technology to a marine engine although it has no throttle valve, considering that combustion conditions may improve with higher load for each cylinder. One cylinder cut and two cylinder cut were tested on a 7 cylinder engine (7S65ME-C) at MES Tamano factory. Date as well as related observations are presented.
In order to reduce smoke emissions from coconut oil methyl ester (CME), the fuel properties, ignitability, combustion characteristics, and exhaust emissions of CME with 1-butanol (CME/1-butanol=60/40 mass %) were investigated using a single cylinder DI diesel engine. CME/1-butanol has a pour point of -12.5°C, which is lower than that of CME. Three other blends tested were rapeseed oil methyl ester (RME)/1-butanol, palm oil methyl ester (PME)/1-butanol, gas oil/1-butanol, where 1-butanol content represents 40 mass%. Thermal efficiency of CME/1-butanol is almost the same as that of gas oil. Although CME/1-butanol has longer ignition delay and higher HC and CO emissions, especially at low load conditions, the smoke emission of CME/1-butanol is lowest among the test blends due to its higher oxygen content. From the experimental results obtained, CME/1-butanol can be considered as a promising alternative diesel fuel.
The single-propeller/twin-rudder system composed of a single propeller and two high-lift rudders of fish-tail type (VecTwin system) has been installed on many vessels in Japan. With this system, a ship can be maneuvered at any mode including going astern, hovering, dead slow forwarding and turning by means of various rudder angle combinations, with the propeller revolution kept in the forward direction. To improve propulsive efficiency of the single-propeller/twin-rudder system, a pair of reaction fins is attached between two rudders where the propeller slipstream passes. Performance of the reaction fin system is discussed. The design practice to determine fin size and form is presented.
Experiment to investigate the dispersive effects of underwater dispersant, namely, the reduction of rise velocity of oil droplets and the increase of diffusion area, have been carried out. A beaker test of mixed sample of Marine Diesel Fuel (MDF) and dispersant was carried out and the particle size distribution was measured to confirm the pertinent ratio of dispersant. As the dispersant is a solution of nonionic surfactant and hydrocarbon solvent, the relation between hydrocarbon solvent and MDF was investigated by Gas Chromatography (GC) analysis. The oil concentration in water was confirmed to be linear to the oil dispersant ratio. As the dispersant reacts to water, the mixed sample of MDF and dispersant was discharged from the nozzle installed at the bottom of a water tank 3 m in height. The behavior of this mixed sample was analyzed by high resolution camera. PTV, PIV, and concentration change method were used to analyze the rise velocity and diffusion area of the sample. It turned out that the reduction of rise velocity of oil droplets and the increased diffusion area of the sample were the effect of the dispersants. Furthermore, the rise velocity of oil droplets was estimated from the size of oil particles.
Simulation of the merging process of two diesel sprays which is a time-consuming task was accelerated using the so-called General-Purpose computing on a GPU (Graphics Processing Unit).The calculation bottleneck was identified as the deterministic judgment model of droplet collision, which seems imperative for a complicated injection system such as that of a Direct Water Injection (DWI) system. The calculation algorithm of the judgment model was carefully modified from that designed for a conventional CPU (Central Processing Unit), and the acceleration was so evident in certain cases that total calculation time was reduced down to nearly one-fourth of the equivalent CPU calculation.