PRIMARY ATOMIZATION AND SPRAY ANALYSIS OF COMPOUND NOZZLE GASOLINE INJECTORS

This work addresses primary atomization modeling, multidimensional spr ay prediction, and flow characteristics of compound nozzle gasoline in jectors. Compound nozzles are designed to improve the gasoline spray q uality by increasing turbulence at the injector exit. Under the typica l operating conditions of 270-1015 kPa, spray atomization in the compo und nozzle gasoline injectors is mainly due to primary atomization whe re the flow turbulence and the surface tension are the dominant factor s. A primary atomization model has been developed to predict the mean droplet size far downstream by taking into account the effect of turbu lent intensity at the injector exit. Two multidimensional spray codes, KIVA-2 and STAR-CD, originally developed for high-pressure diesel inj ection, are employed for the lower-pressure gasoline injection. A sepa rate CFD analysis was performed on the complex internal flows of the c ompound nozzles to obtain the initial and boundary conditions for the spray codes. The TAB breakup model used in KIVA-2 adequately facilitat es the atomization process in the gasoline injection.