Flash-boiling occurs when a fuel is injected into a combustion chamber where the ambient pressure is lower than the saturation pressure of the fuel. It has been known that flashing is a favorable mechanism for atomizing liquid fuels. On the other hand, alternative fuels, such as gaseous fuels and oxygenated fuels, are used to achieve low exhaust emissions in recent years. In general, most of these alternative fuels have high volatility and flash-boiling takes place easily in the fuel spray when injected into the combustion chamber of an internal combustion engine under high pressure. In addition the multicomponent mixture of high-and low-volatility fuels has been proposed in the previous study in order to control the spray and combustion processes in an internal combustion engine. It was found that the multicomponent fuel produces flash-boiling with an increase in the initial fuel temperature. Therefore, it is important to investigate these flash-boiling processes in fuel spray. In the present study, the submodels of a flash-boiling spray are constructed. These submodels consider the bubble nucleation, growth, and disruption in the nozzle orifice and injected fuel droplets. The model is implemented in KIVA3V and the spray characteristics of multicomponent fuel with and without flashing are numerically investigated. In addition, these numerical results are compared with experimental data obtained in the previous study using a constant volume vessel. The flashing spray characteristics from numerical simulation qualitatively show good agreement with the experimental results. In particular, it is confirmed from both the numerical and experimental data that flash-boiling effectively accelerates the atomization and vaporization of fuel droplets. This means that a lean homogeneous mixture can be quickly formed using flash-boiling in the combustion chamber. (C) 2006 Wiley Periodicals, Inc.
