Empirical Investigation of Reactivity-Controlled Compression Ignition Engine Fuelled by Ethanol and DME at Low Engine Load

Abstract

Abstract Low-carbon fuels can reduce the carbon footprint within the transportation sector significantly. Upcoming emission regulations challenge diesel-fueled combustion engines, especially concerning NOx and smoke. Combustion strategies that enable low-temperature combustion can realize low NOx and soot emissions, simultaneously. Reactivity-charged compression ignition (RCCI) mode enables a range of applicable fuels and can perform with a wider load range. However, challenges persist with poor combustion efficiency at low-load RCCI. This work studies the dual-fuel combustion of high-pressure direct injection DME with port-fueled ethanol. The injection timing of DME was advanced until the RCCI combustion mode was apparent. The influence of premixed energy share (PES) of ethanol was compared under a similar load. Combustion and emissions were characterized by in-cylinder pressure measurement and exhaust emissions speciation. In a conventional dual-fuel combustion mode, the major proponent of exhaust hydrocarbon emissions was unburned ethanol. The advance of the injection timing lowered the proportion of unburned ethanol in the exhaust similarly among premixed energy shares. As a result, an 11% absolute increase in combustion efficiency was realized with an advanced injection timing from 355°CA to 300°CA. The NOx emissions were reduced. By employing a split injection strategy, RCCI pressure rise rates and NOx emissions could be further minimized. The results show that optimized fuel scheduling of DME-ethanol RCCI may establish low NOx and ultra-low smoke emissions with high combustion efficiency.