The fluid flow characteristics inside compound silicon micro machined port fuel injector nozzles were analyzed through the use of computational fluid dynamics (CFD). This study was undertaken in order to gain a better understanding of the fluid mechanics taking place in the compound orifice plate. In addition, the calculated computational results will be used to predict the fuel spray patterns and sauter mean diameters of the sprays. The influence of orifice plate geometry on calculated turbulent kinetic energies and fuel spray patterns was also studied and will be discussed.The results of this investigation indicate that the fluid flow characteristics inside the compound silicon micro machined port fuel injector nozzle are influenced by the geometries of the compound orifice plate, and that the flow characteristic inside the orifice plate effect the type of spray produced by the injector. Of particular importance is the cavity geometry of the compound orifice plate and the placement of the turbulence generator(s) with respect to the metering orifices.Experimentally measured fuel spray droplet sizes were predicted by using average calculated turbulence levels. The calculated computational results were also used to replicate the type of spray that the injectors produced during experimental testing.