Application of methanol and optimization of mixture design over the full operating map in an intelligent charge compression ignition (ICCI) engine

Abstract

Application of methanol and mixture design of the dual-fuel intelligent charge compression ignition (ICCI) was investigated over the full operating range. ICCI engine (an originally 5.3 L turbocharged diesel engine) equipped with two direct-injection systems and a supercharged system realized real-time design of dual-fuel stratification and was investigated compared with conventional diesel combustion (CDC). Engine operating map and control strategy was obtained, and combustion characteristics and original emissions were analyzed. Results showed that the thermal efficiency of ICCI was 1% to 3% higher than that of CDC in the load range of 6–14 bar IMEP. Increasing load over 14 bar IMEP, a triple-injection strategy of methanol was applied where the last injection was near the top dead center. Except for high speed and low load conditions, ICCI mode realized controllable combustion (coefficient of cyclic variation below 5%, maximum pressure rise rate below 15 bar/°CA, and peak pressure below 180 bar). The maximum thermal efficiency was 53% under low speed and high load conditions, while the minimum NOx emissions were 0.17 g/kWh occurring in the same conditions. Nucleation particles dominated the formation of particle emissions and were minimized under high speed and medium load conditions (below 1.3 × 106/cm3).