Study on Combustion Improvement of Low-Grade Bunker Fuel Oil by Auxiliary Hydrogen Injection

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In the first year (2001), researchers mainly focused on the investigation of combustion problem caused by low-grade bunker fuel oil and the construction of hydrogen injection system. Results from the investigation study were summarized as experimental reports presented in the several international conferences. The problems with low-grade fuel resulted in two aspects ; one is its longer ignition delay that has almost three times as long as normal BFOs and the other is its slower burning speed that is never enough for spray flame to go up toward the injection nozzle. Important information about hydrogen injection system was also obtained in such occasions through discussions with other researchers.In the second year (2002), characteristics of hydrogen-assisted combustion were visually investigated in detail. Unique feature of combustion promoting effect of hydrogen was unveiled. When hydrogen is injected just after the fuel injection, ignition of hydrogen sometimes happens in the vicinity of nozzle tip and after the ignition fuel spray was immediately covered by the luminous flame because of rapid propagation of hydrogen flame, which reduces total combustion period drastically. To purpose reducing PM emission, which is thought to be final unburnt products of combustion, hydrogen was injected just before the end of fuel injection. The result showed that disturbance caused by the rapid expansion of hydrogen/air mixture and its higher combustion temperature helped the reduced to burn completely and generate considerably less smoke.On the whole, this research was successfully concluded on both conception and verification sides.