Turbocharging Effects on Emissions Reduction and Thermal Efficiency under Diesel/Natural Gas Dual-fueled Combustion

Dual-fueled combustion, using high and low reactivity fuels simultaneously, is a promising combustion method that enables reduction of nitrogen oxides (NOx) emission. However, the total amount of NOx emissions in the exhaust gas is strongly influenced by the overall excessive air ratio (lambda) of air-fuel mixture. Thus, lean mixture condition is important for NOx emissions although RCCI operating condition is applied. In addition, not only reduction of emissions, but improvement in BTE requires the boost pressure to be increased. Thus, variations in boost pressure via a controlling turbocharger system was evaluated under general dual-fueled combustion and RCCI conditions using diesel and natural gas fuels while tracing emissions and BTE. The results indicated that higher boost pressure was more effective on RCCI condition in reducing NOx emissions and enhancing BTE and turbocharging system efficiency with lower carbon dioxides, compared to those of general dual-fueled combustion condition. Especially, turbocharger efficiency of dual-fueled combustion was higher than that of diesel single-fueled combustion related with composition of exhaust gas and exhaust gas temperatures.