Development and Validation of a Primary Breakup Model for Diesel Engine Applications

Fuel injection characteristics, in particular the atomization and penetration of the fuel droplets in the region close to the nozzle orifice, are known to affect emission and particulate formation in Diesel engines. It is also well established that the primary fuel atomization process is induced by aerodynamics in the near nozzle region as well as cavitation and turbulence from the injector nozzle. Typical breakup models in the literature however, do not consider the effects of cavitation and turbulence from nozzle injector. In this paper, a comprehensive primary breakup model incorporating the inner nozzle flow effects such as cavitation and turbulence along with aerodynamically induced breakup is developed and incorporated in the CONVERGE CFD code. This new primary breakup model is tested in a constant volume spray chamber against various spray data available in the literature. Both evaporating and non-evaporating spray conditions are investigated since a non-evaporating spray provides a more stringent test for spray models, while evaporating spray represents a more realistic engine environment. X-ray data obtained from the Advanced Photon Source is used for a detailed validation of this primary breakup model, especially in the region close to the nozzle under non-evaporating conditions. Specifically, spray cone-angle, liquid penetration, transverse mass distribution, and normalized spray axial velocity are matched. Robust validation is performed under evaporating conditions against liquid length, and penetration data. Very good agreement is observed under all the conditions attesting the new primary breakup model's capability to capture the primary breakup phenomenon effectively.