Spray characterization of a swirl-type injector for gasoline direct injection engines

To understand the spray characteristics that are related to the characteristics of economy, emission and the combustion of direct injection engines, the sprays into constant volume chamber within different back pressure value from a swirl type gasoline direct injection (GDI) injector were visualized. The spray development, spray penetration, spray cone angle, spray tip velocity and droplet characteristics were measured at various injection pressure, ambient back pressure and at different injection durations. Experimental results showed that under the low back pressure ambient conditions, the spray behaviour shows a hollow cone with wide spray angle and initial spray slug at the tip which satisfied the mixing control concept of achieving homogenous mixture preparation, while the spray exhibits a solid cone in the case of high back pressure which satisfied the stratified mixture preparation concept. Tumble vortexes in the opposite direction exist in the rear part of the spray under low back pressure ambient conditions while the vortexes form in the middle part under high back pressure ambient conditions, these vortexes are helpful for fuel evaporation, diffusion and forming ignitable mixture especially near the spark plug.