To improve the fuel consumption and exhaust emission for gasoline engines, Gasoline Direct Injection (GDI) system was spotlighted to solve above requirements. Mixture preparation strategy is intimately related to the fuel injection system. At high strength of swirling motion in pressure swirl atomizers, an air core will appear inside of the atomizer. Thus, a two-phase flow will be present inside of the atomizer. In this study, the volume-of-fluid (VOF) method is used to simulate the internal flow of pressure-swirl atomizers. In order to investigate the effects of orifice geometry and swirl angle on flow characteristics of simplex pressure-swirl injectors, several three-dimensional simulations were done. The effects of length to diameter ratio of the orifice, orifice diameter and swirl angle have been studied on the atomization characteristics such as spray cone angle and discharge coefficient. It was observed that by increasing the orifice diameter and orifice length to diameter ratio, and also by decreasing the swirl angle, the spray cone angle decreases. However the discharge coefficient increases. Monitoring the rate of the variations leads to an approach for optimized geometry of simplex pressure-swirl atomizers.

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