Abstract
To examine the feasibility of performance improvement by highly flexible fuel injection, a series of experiments were performed using a single-cylinder diesel engine with a dual injector system which includes two sets of common-rail injection systems. This system enables variable injection rate for each injection pulse and a wide-range dwell between injection pulses, i.e. even negative injection dwell can be performed. Experiments with multi-stage injection were conducted with various injection pressures, injection timings, and injection quantities. The results show that switching injector for pilot and main injections reduces smoke emission, and a higher pilot injection pressure increases CO emission without a reduction of smoke emission, while a higher main injection pressure reduces smoke emission with no increase in CO emission. Split-main injection with zero injection dwell increases thermal efficiency under high injection pressure condition. However, negative injection dwell markedly increases smoke emission owing to the spray-to-spray interaction.
