PREDICTING DROPLET SIZE AND SPRAY ANGLE OF A FUEL SPRAY FROM AN AUTOMOBILE FUEL INJECTOR WITH MULTI-SWIRL NOZZLES

A fuel injector with multi-swirl nozzles for finely atomizing a fuel spray in a gasoline engine was developed. The multi-swirl nozzles are composed of swirl chambers placed in the upstream of each orifice which is an outlet of injector. The swirl flow produced by the swirl chambers fauns thin liquid films on the walls of the orifices by centrifugal force, and these films break up into small droplets outside the orifices. In this study, fuel flow within the swirl nozzle was simulated by using the volume of fluid (VOF) method, and the simulated velocities and width of the thin liquid film were used to predict the droplet size and spray angle of the fuel spray. Miyamoto's atomization model was applied to connect a circumferential velocity and a width of the liquid film at the orifice outlet with the droplet size. It was found that the droplet size and spray angle of multi-swirl nozzles can be predicted by using the VOF method and Miyamoto's atomization model.