Influence of Nozzle Geometry on Spray Atomization and Shape for Port Fuel Injector

Understanding the disintegration process and geometric effects on spray characteristics are of importance in the design of a high quality injector, because improving fuel atomization and targeting has been proved to be an effective way to reduce the exhaust hydrocarbon emissions for gasoline engines.

To reveal the relationship between the internal flow and the spray characteristics, particle size measurements and computational fluid dynamics (CFD) were combined to analyze a set of orifices. The flow field inside the nozzle, as well as the direction and shape of the liquid jet in the vicinity of the nozzle exit, was numerically predicted. Spray droplet sizes were then measured for the same orifices. Interesting links were discovered between nozzle geometry and spray characteristics. The results indicate that the secondary flow inside the orifice hole, due to Vena Contracta phenomena, contributes greatly to the atomization and shape of the liquid jets. Atomization quality can be significantly improved by controlling the orifice hole location and its length to diameter ratio (L/D).