Simulation numérique de l'injection de carburant et de sa désintégration dans les moteurs Diesel

The purpose of this study is to compare four models of secondary breakup of droplets: the Taylor Analogy Breakup model (TAB), the Kelvin-Helmholtz and Rayleigh-Taylor model (KHRT), the Pilch-Erdman model (PE) and the Schmehl, Maier and Witting model (SHF) ; this is based on an experimental model following the initial and boundary conditions of spray A developed by the Sandia laboratory. The main scientific issues from spray injection to liquid droplet vaporization in a turbulent environment are exposed through several series of Large-Eddies Simulation (LES), performed using the "sprayFoam" solver of the CFD software "OpenFOAM". The results are analyzed with respect to liquid and fuel vapor penetration lengths, fuel vapor mass fractions, temperature and flow velocity profiles. The TAB model was found to have better n-dodecane liquid and vapour penetration predictions than the other three models, although it overestimates the vapour and liquid penetration lengths as much as the other three models over most of the injection time. This model is chosen for the parametric study on injection pressure; four pressure values are investigated: 100, 120, 150 and 170 MPa. The results show that the injection pressure has a favourable effect on vapour penetration, and therefore on the mixing between the fuel vapour and the surrounding gas, but this effect is not without limits, since, or 150 MPa in our case, that penetration is strongly influenced by turbulence.