天然ガスを吸入する二元燃料ディーゼル機関の燃焼特性
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概要
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This paper investigates the performance, exhaust emissions, and combustion characteristics of a dual fuel diesel engine fueled by CNG (Compressed Natural Gas) as the main fuel. The CNG supply rate was defined as the heat energy ratio of the supplied CNG to the total heat energy available in the cylinder. The results showed that the brake thermal efficiency was similar to that of ordinary diesel operation at BMEP=0.67MPa even when the CNG supply rate was raised to 74%. When the CNG supply rate was higher than 75% ignition became very unstable and the brake thermal efficiency decreased significantly as well as the HC emissions increased sharply. The reason for this is considered to be that the appearance of miss fire cycles gave rise to combustion fluctuations. To reduce NOx emissions, the effects of intake air dilution with nitrogen gas were also investigated.