A Turbulence and Cavitation Induced Breakup Model for Fuel Spray Modeling 2014-01-2737
Fuel spray atomization process is known to play a key role in affecting mixture formation, combustion efficiency and soot emissions in direct injection engines. The fuel spray Computational Fluid Dynamics (CFD) modeling technology can be an effective means to study and predict spray characteristics such as penetration, droplet size and droplet velocity, and as a consequence, to drastically reduce experimental work during the engine development process. For this reason, an accurate numerical simulation of the spray evolution process is imperative. Different approaches and various models based on aerodynamically induced breakup mechanism have been implemented to simulate spray atomization process in earlier studies, and the effects of turbulence and cavitation from the injector nozzle is recently being concerned increasingly by engine researchers.
In this study, an enhanced turbulence and cavitation induced primary breakup model combining aerodynamic breakup mechanism is developed. The proposed model improves the primary breakup accuracy by optimizing the turbulence induced breakup process, controlling the transition process of the primary and secondary breakups and employing a new child droplet size function and a new parent droplet size reduction rate. The aerodynamic secondary breakup model has been modified to incorporate with the proposed model is coupled to simulate the complete spray evolution and better predict the secondary droplet size and velocity.
This new model is validated with the High-Speed Imaging and Phase Doppler Particle Analyzer (PDPA) experimental results of the full-cone diesel spray in a constant volume vessel under non-evaporating and various injection conditions. Simulation results of the new model exhibits a good agreement with respect to spray penetration, droplet average mean diameter, droplet velocity under all the test conditions and shows an obvious improvement for fuel spray modeling.