Reactivity-Controlled Compression Ignition Combustion at Different Intake Charge Temperatures and Exhaust Gas Recirculation

In the last few years, reactivity-controlled compression ignition (RCCI) mode combustion has gained researchers’ attention due to its superior performance, combustion, and emission characteristics compared to other low-temperature combustion (LTC) strategies. In this study, RCCI mode combustion investigations were carried out to explore the effects of exhaust gas recirculation (EGR) and intake charge temperature (ICT) on combustion, performance, and emission characteristics of a mineral diesel/methanol-fueled engine. In this study, constant engine speed (1500 rpm) and load (3 bar brake mean effective pressure [BMEP]) were used to perform the engine experiments. The premixed ratio (r_p) of methanol was varied from r_p = 0 to r_p = 0.75, where r_p = 0 represents the baseline compression ignition (CI) mode combustion using diesel as fuel. At all r_p, EGR rate and ICT were varied from 0 to 30% and 40° to 80°C, respectively. Experimental results exhibited that increasing the EGR was useful in RCCI mode combustion up to medium r_p; however, at higher r_p, increasing the EGR resulted in incomplete combustion, leading to more hydrocarbon (HC) and carbon monoxide (CO) emissions.

In contrast to EGR, increasing the ICT was more suitable at higher r_p, leading to a greater degree of combustion completion. Detailed particulate investigations were performed, which exhibited that increasing the r_p resulted in relatively lesser particle emissions. At all r_p, increasing the EGR up to 15% led to relatively lower particle emissions; however, a higher EGR of 30% resulted in relatively higher particle emissions. Increasing the ICT resulted in higher particulate emissions; however, at higher r_p, EGR and ICT variations were less effective than lower r_p. Several qualitative correlations between different particulate characteristics revealed that intermediate EGR (15%) at intermediate ICT was the most suitable condition for optimized RCCI mode combustion.