Effect of EGR and Premixed Mass Percentage on Cycle to Cycle Variation of Methanol/Diesel Dual Fuel RCCI Combustion

Reactivity controlled compression ignition has been a proven combustion strategy for better reduction of NO_x and PM emissions without compromising the fuel economy. However, the combustion strategy still need more investigation to overcome its operational stability. In this study, the influence of hot/cooled exhaust gas recirculation and premixed mass percentage and there cyclic variation of Methanol/Diesel dual fuel reactivity controlled compression ignition (RCCI) combustion was investigated in a modified 3 cylinder light duty, turbocharged, CRDI diesel engine. Methanol/Diesel RCCI combustion was achieved by premixing methanol with intake air in the intake port and injecting diesel directly into the cylinder by flexible common rail direct injection system. The intake manifold was altered to adopt port fuel injection of methanol and EGR. Experiments were conducted at 3.4 bar and 5.1 bar BMEP at 1500 rpm by varying EGR and premixed mass percentage. Overall, the results shows that 26% cooled EGR resulted in less cycle to cycle variation, better reduction in NO, and smoke emissions with improved thermal efficiency at both loads with methanol mass percentage 76% and 81% respectively. At hot EGR operation the higher cyclic variation, higher pressure rise rate and higher NO_x and smoke emissions observed than cooled EGR operation. It is also observed that 5.1 bar BMEP operation exhibited a lesser cycle to cycle variation and emissions compared to 3.4 bar BMEP operation.