Effects of injector configurations on RCCI mode of combustion in a light-duty diesel engine

Abstract

Reactivity controlled compression ignition (RCCI) is a promising low temperature combustion technique that reduces nitrogen oxides (NOx) and soot emissions simultaneously in diesel engines. This experimental study examines the impact of injector configurations on combustion, performance and emissions of a light-duty diesel engine using compressed natural gas (CNG)-diesel RCCI combustion. Injectors with six, seven and eight holes were tested across low load using a single injection strategy and intermediate loads with a double-injections strategy at 1500 and 2800 rpm, with a start of injection (SOI) sweep. The work aims to address key fundamental questions such as (a) how injector configurations affect combustion phasing, engine-out emissions and associated trade-offs, (b) how single and double injection strategies influence above mentioned outcomes; and (c) whether the performance be further improved while preserving the inherent advantage of low NOx and soot emissions in the RCCI strategy. The six-hole injector showed higher peak heat release rates at low loads, while the eight-hole injector showed higher peak heat release rates at intermediate loads. The six-hole injector exhibited the shortest ignition delay and advanced combustion phasing, with a longer combustion duration compared to the seven-hole and eight-hole injectors. The eight-hole injector had higher combustion efficiency at low loads but underperformed at intermediate loads. Carbon monoxide and unburned hydrocarbons emissions were higher for the six-hole injector at low loads and for the eight-hole injector at intermediate loads. NOx and soot emissions were decreased with increase in injector hole numbers.