Effect of the inert gas addition on the combustion and emissions characteristics of natural gas/diesel dual-fuel engine

: Shale gas, which is mainly based on methane, has become one of the important future energy sources that serve as substitutes for conventional fossil fuels. Since methane has lower carbon content, as compared to that of gasoline and diesel, in the same energy density, carbon dioxide could be reduced. In addition, it can decrease smoke emission. However, shale gas contains not only methane, but also inert gases, such as nitrogen and carbon dioxide. For this reason, we investigated the effect of inert gas on the combustion and emission characteristics in a natural gas/diesel dual-fuel engine. The engine was operated with fixed engine speed and load conditions of 2,000 rpm/100 kW. The ratio of inert gas to natural gas was controlled from 0 % to 10 %. The substitution ratio of natural gas to diesel was set to 80%. Diesel injection timing was varied from TDC to 12° CA BTDC. The results showed that the nitrogen oxide and smoke emission were significantly reduced by the addition of the inert gas due to its high heat capacity.