The characteristics of free spray of a new type high-pressure-swirl injector in gasoline direct injection (GDI) engine under various injection conditions are investigated. The fuel spray with hollow-cone structure, wide spreading, and large spray angle is observed under the injection condition simulating to the GDI engine operation at full load. The study shows that a vortex structure can be clearly observed in the periphery of the spray. Meanwhile, an initial spray slug also appears at the tip of the main spray. Under the injection condition of GDI engine partial load, the structure of fuel spray changes into the more compact and solid-cone shape with decreased spray width. Moreover, the influences of the injection pressures and ambient pressures on the spray characteristics of the injector are studied. Along with the experimental studies, a general numerical model for the swirl spray is developed. Then, the model is implemented into a multi-dimensional computational fluid dynamics code (KIVA-3V) to theoretically study the pressure-swirl injector sprays. Comparisons between the computed and measured spray characteristics such as spray structure, spray tip penetration, and droplet sizes are made, and good agreement has been achieved between the model prediction and measurement.
