Pilot Injection Model for Small Diesel Cylinder

Pilot spray formation process has been analyzed by simulation. Investigating the influence of injection phasing and engine speed on vapor preparation process, the attention has been focused on fuel evaporation within cylinder. Once such a phase had been concluded, the indications on fuel shot evolution have been extrapolated and the obtained results have been used in the lumped parameter modeling of pilot spray evaporation. As the main driving factors regard both the injection system operation (injection pressure, needle opening, nozzle hole diameter and shape, fuel properties) and the in-cylinder conditions (in terms of pressure, temperature and charge motion), different simulation tools have been used. The complete injection system operation has been modeled with a 0-1D approach; the effect of nozzle flow conditions have been investigated by 3D-CFD transient simulations; the in-cylinder conditions and pilot shots evolution have been modeled by detailed 3D-CFD simulation of intake and compression strokes, in order to quantify the intensity of swirl-squish structures and their interaction, as well. The details of model approach have been described and the obtained results have been presented and discussed.