Experimental and simulation study of methanol/coal-to-liquid (CTL) reactivity and combustion characteristics of diesel engines in RCCI mode

An experimental and simulation study of the RCCI combustion mode of coal-based fuels (methanol prepared from coke oven gas/coal-to-liquid, Methanol/CTL)) was carried out on a modified dual-fuel compression ignition (CI) engine. The mechanism by which Methanol/CTL, which has a significant difference in reactivity, promotes engine combustion and thermal efficiency is revealed. The results show that with the increasing load (i.e., load recovery ratio (LRR)) supplied by methanol, the reactivity gradient inside the cylinder increased from 28% to 451%, and the area of the ignition region was rapidly enlarged, and the reactivity of the ignition region increased. The HC and CO emissions increase by 1350% and 6866%, while the soot and NOX are reduced by a maximum of 25% and 15%. The reactivity of the ignition region increased by 8% to 26 %. Diffusion combustion forms a strong linear correlation with reactivity, with a maximum reduction of about 30 times in the premixed-to-diffusion combustion ratio. Concentration of the exothermic centre towards the top-dead-centre (TDC) is increased by a maximum of 18%, with an increase in the coefficient of variability (COV) by a maximum of 90%, indicative thermal efficiency (ITE) by a maximum of 22% and brake thermal efficiency (BTE) by a maximum of 17%. The LRR does not exceed 50% while the engine maintains stable operation and 30% while maintaining power and fuel economy.