The influence of airflow on fuel spray characteristics from a slit injector

Optimization of fuel spray, airflow, and their interaction with the cylinder and piston wall is crucial to achieve stable combustion of stratified charge with minimum emissions in direct-injection spark-ignition (DISI) engines. In this study, the interaction between air and fuel spray from slit injector was investigated in a steady airflow system generated by a wind tunnel under atmospheric conditions. Both Mie scattering images and phase Doppler anemometry (PDA) measurements of the spray were analyzed for different air velocities. Three-dimensional computational fluid dynamics (3-D CFD) have been employed to further explain the mutual interaction between air and spray. It was found that increasing the airflow velocity across the spray results in a significant change in the bottom part of the spray while a slight change was observed close to the nozzle exit. The variation in spray geometry, which is mainly attributed to an aerodynamic effect and to extracted droplets from the main spray by the airflow effect, was evaluated and presented for different air velocities. The spray droplet size redistribution within the spray plume was investigated, and regions with smaller and larger droplets were identified and discussed. The results indicate that the effect of airflow pattern on droplet size distribution within the spray is a considerable factor in the optimization of airflow and spray together. This could be considered in achieving a limited ignitable region without much diffusion of smaller droplets to the non burning zone during the part load operation of DISI engines.