The Prediction of Flash Atomization in GDI Multi-Hole Injectors

A 1D flash evaporation model is being developed to capture the effects of bubble nucleation and growth inside multi-hole injector nozzles to investigate the flash evaporation in fuel injector sprays in Gasoline Direct Injection (GDI). The 1D nozzle flow model helps to understand the effects of main physical and geometrical parameter in promoting the fuel flash evaporation. This model is based on a weakly compressible homogenous two-phase mixture assumption. A non-equilibrium model is used to predict the vapour formation rate along the nozzle. A fully explicit method based on a two-step Lax-Wendroff method is used together with a TVD scheme. An atomisation model has been proposed to correlate the void fraction at nozzle exit to probability function of the liquid droplets generated from flashing atomisation. An accurate two phase speed of sound is adopted allowing one to predict the choked flow conditions once saturation has been reached. Metastable state are not considered in this first approach. An extensive assessment of model capability considering both a basic test case with water injection and an engine-like gasoline injection.