Atomization of High-Pressure Diesel Spray: Experimental Validation of a New Breakup Model

A hybrid model for the atomization of Diesel sprays was developed [1]. The model was added to the KIVA code to better simulate spray evolution. Different implementation for low-medium and high injection pressure sprays are performed. It has already been validated for the low-pressure case [1,2] and in this work it was tested for high injection pressure systems, in a vessel at ambient conditions. It distinguishes between jet primary breakup and droplet secondary breakup. For the latter distinct models are used, as the droplet Weber number changes in the various regimes, in order to take into account the effects of the different relevant forces. For high pressure Diesel spray the effects of jet turbulence, cavitation and nozzle flow on liquid core primary breakup must be considered. Due to the high droplet velocity the catastrophic secondary breakup regime may occur. Inclusion of the Rayleigh-Taylor accelerative instabilities in competition with Kelvin-Helmholtz is therefore necessary to model high Weber number droplets secondary breakup.

The experimental data used for the tuning of the model and for the comparison of the results are pertinent to a commercial high pressure, electronic controlled, injection system (Bosch Common Rail) for automotive Diesel engines. The investigation procedure exploits a light sheet technique based on a Nd-Yag pulsed laser and a synchronized CCD camera [3, 4 and 5]. The measured characteristics are the spray penetration and the spray cone angles, as the fuel jet evolves in an atmospheric chamber.