COMBINED SPRAY MODEL FOR GASOLINE DIRECT INJECTION HOLLOW-CONE SPRAYS

Piezoinjectors with outwardly opening nozzles are the latest generation of high-pressure injectors for gasoline direct injection (GDI). In this study, a combined Eulerian-Lagrangian spray model is presented, which is based on user-defined implementations of all key models within a Fluent framework. Primary and secondary breakup is modeled with a combined LISA-KH-TAB approach. The LISA primary breakup model is extended by a one-dimensional model of the nozzle flow and by modified momentum source terms that lead to a more reasonable prediction of the near-nozzle continuous phase flow field. The KH and TAB secondary breakup models are applied to high and low Weber number secondary breakup, respectively. The collision model implemented accounts for all relevant collision regimes (i.e., coalescence, stretching separation, reflexive separation, and bouncing). For the bouncing and reflexive separation regimes, the momentum equations are modified because the standard equations cannot predict the trajectories after off-center collisions of differently sized droplets. Vaporization is modeled with a single-component model, which employs an analytical solution of the coupled heat and mass transfer equations. The combined model is validated with light scattering visualization and light sheet measurements, phase-doppler anemometry (PDA), and laser correlation velocimetry (LCV) at pressurized vaporizing- and nonvaporizing conditions. The validation indicates a good agreement of both macroscopic and microscopic properties, such as the spray geometry, vortex positions, or drop size distributions.