Reactivity Controlled Compression Ignition (RCCI) Combustion Engine Characteristics Fuelled with Diesel/Compressed Natural Gas (CNG) and Diesel/Methanol Fuel Pairs

Ultra-low oxides of nitrogen (NOx) and particulate matter (PM) characteristics of reactivity controlled compression ignition (RCCI) combustion has motivated the researchers to explore more so that this can be implemented using a long range of alternative fuels. In this study, a comparative analysis of combustion, performance, and emission characteristics of RCCI combustion fuelled with diesel/compressed natural gas (CNG) and diesel/methanol fuel pairs have been carried out with respect to baseline compression ignition (CI) combustion. All experiments were performed in a constant speed engine at four different engine loads. The RCCI combustion experiments were performed at a constant premixed ratio (rp) of 0.50 and 15% exhaust gas recirculation (EGR). The results exhibited a significant reduction in oxides of nitrogen (NOx) emissions and relatively smoother RCCI combustion compared to baseline CI combustion. RCCI mode combustion resulted in relatively superior engine performance compared to baseline CI combustion, especially at higher engine loads. Effect of gaseous fuel (CNG) as low reactivity fuels (LRF) in RCCI combustion in comparison to liquid fuel (methanol) as was the main objective of this experimental study. Comparison of RCCI combustion fuelled with CNG and methanol as LRF showed slightly higher brake thermal efficiency (BTE) of diesel/CNG fuelled RCCI combustion compared to diesel/methanol fuelled RCCI combustion. The combustion characteristics of diesel/CNG fuelled RCCI combustion was found more stable compared to diesel/methanol fuelled RCCI mode combustion.