Turbocharged diesel/CNG Dual-fuel Engines with Intercooler: Combustion, Emissions and Performance

A yc6112ZLQ turbocharged 6 cylinder engine with intercooler was converted to operate in dual fuel mode with compressed natural gas (CNG) and pilot diesel. The influence of the CNG ratio, pilot diesel injection advance (ADC) and intake temperature after intercooler on the combustion process, emissions and engine performance was investigated. The results show that the combustion process of dual-fuel engines is faster than diesel engine. Both the ignition timing of the pilot fuel and the excess air ratio of total fuel λ dominate the combustion characteristics of duel-fuel engines. With the increase of CNG ratio, the pressure and temperature in cylinder decrease at rated mode, but increase at torque and low speed modes. With advanced the pilot injection timing or increased the intake temperature, the cylinder pressure and temperature increase. The results also show that CNG ratio, pilot injection timing and intake temperature dominate the pollutant emissions and engine performance of dual-fuel engines. With the increase of CNG ratio, NO_x emissions will be increased at torque and low speed modes, but decreased at rated mode, soot emissions will be decreased, while the brake specific fuel consumption (BSFC) will be increased. With advanced the pilot injection timing or increased intake temperature, NO_x emissions will be increased, while BSFC will be decreased. Those results of this study provide a useful theoretical basis for optimizing the combustion process of turbocharged diesel/CNG dual-fuel engines with intercooler.