Modelling of primary breakup process of a gasoline direct engine multi-hole spray

This paper proposes a numerical methodology for the simulation of a gasoline spray generated by amulti-hole injector of a current production wall-guided gasoline direct injection engine. Particularcare is dedicated to the accurate representation of the spray primary breakup by means of an atomizationmodel. The model is purposely implemented to take into account cavitation phenomena andturbulent effects induced by the nozzle geometry through a simplified approach. Because a high primarybreakup rate is expected, an initial distribution of atomized droplets is predicted at the nozzlehole exit by the numerical approach. The spray is at first experimentally investigated in a test vesselat non-evaporative ambient conditions and under quiescent conditions, in which commercial gasolineis injected at two different injection pressures (10.0 and 20.0 MPa). The spray is characterizedin terms of both the instantaneous mass flow rate and morphology. Numerical simulations are performedand then compared against the experiments in order to evaluate their capability to correctlypredict liquid spray penetration, droplet-size distribution, and spray morphology. The new approachis a fairly simple, yet reliable, solution that is able to predict the influence of the nozzle hole (in termsof the discharge coefficient, diameter, and length), neglecting geometrical details that are usually farfrom being easily accessed by engine developers