Initial breakup and atomization of droplets in diesel fuel sprays

摘要

Because combustion and exhaust emissions in direct injection engines are strongly influenced by fuel-air mixing during the ignition delay period, it is important to investigate the disintegration of fuel flow and droplet formation at a very early stage of injection. In this study, photographs of sprays up to 400 μs from the start of injection were taken using a Nano-spark light source and a newly developed droplet image analysis method. The results show that the contour of the spray suddenly changes into a large-scale structure at about 200 μs after the start of injection. In the sprays before this time, disintegration occurs in narrow areas near the spray tip. However, after this time, branch like structures cause the disintegration. It is observed that many small droplets remain in the vicinity of the nozzle tip in initial sprays up to at least 200 μs.