[in Japanese]

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[in Japanese]

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Because hydrogen emits no carbon dioxide, its use is being promoted as a national policy, and early commercialization of hydrogen engines is expected. However, there are technical issues to be solved, such as combustion control. Many studies have been conducted on the use of hydrogen in internal combustion engines, and small-sized engines have been put to practical use, but basic research knowledge is needed for the practical use of large engines for marine use. In this study, the effects of direct injection from a hydrogen injector on the formation and turbulence of the mixture on combustion were systematically examined through combustion experiments using a constant volume chamber.

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Only a limited number of ships use batteries as a direct power source, but batteries are often necessary when dealing with electrical energy. Overcharging a lithium-ion battery can cause smoke or fire. In practice, an upper limit of the set voltage is set, and if the set value is exceeded, a safety device is activated, and charging is stopped. In pulse charging, the peak value of the voltage due to the pulse tends to reach the upper limit set voltage, and it is considered that charging stops earlier than in constant current charging. In our laboratory, it was confirmed experimentally that the charging effect more than the constant current charging can be obtained by devising the pulse application method. In this study, it was found that pulsed current was more effective than constant current in increasing the amount of charge. With pulse charging, the amount of charge can be adjusted to the set SOC position without causing overcharge. Pulse charging is expected to be applied to a wide range of fully charged batteries due to the effect of pushing the battery charge up to the original SOC position.

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We are focusing on methods for measuring and monitoring engine and its component conditions using vibration sensors installed around the cylinders of marine diesel engines. Measurement targets include exhaust valve motion, fuel injection timing, ignition timing and maximum combustion pressure. In this study, vibration characteristics of a low-speed two-stroke marine diesel engine was investigated during operations of exhaust valve and fuel injection valve. Vibrations of the engine were measured by operating the exhaust valve or fuel injection valve when the engine was stopped. As a result of experiments, it was found that the timing at which the exhaust valve closes and the start and end of fuel injection from the fuel injection valve can be detected using vibration measurement signals. Furthermore, the fuel oil pressure rise in fuel injection pipe can be detected separately from vibration signal of the injection start timing by FFT analysis.

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