Parametric Investigation for NOx and Soot Emissions in Multiple-injection CRDI Engine using Phenomenological Model

The classical trade-off between NOx and soot emissions from conventional diesel engines has been a limiting factor in meeting ever stringent emission norms. The electronic control of fuel injection in diesel engines emerged as an important strategy for their simultaneous reduction. The high pressure multiple-injection in a common rail direct injection system has been promising in this regard. While, the effects of pilot injection or multiple pulses of CRDI injection schedule on simultaneous reduction of NOx and soot have been widely investigated and reported, the investigations concerning three and more injection pulses have been limited. In this paper, the ability of a predictive model, developed by the authors, in providing optimal multiple-injection schedule is demonstrated through parametric investigations. The effects of pilot and post fuel quantity and dwell between the injection pulses on NOx and soot emissions are discussed. The emission predictions from the model are corroborated with available measured data. The comparisons between predicted and available measured data show that while an optimum quantity of pilot fuel reduces NOx emission, the post injection fuel quantity and its dwell from main injection pulse lowers soot emission.