Liquid breakup and droplets behavior of free triple-impinging jets with different impinging distance

The breakup characteristics and droplet behavior of free triple-impinging jets (FTIJs) were investigated using a high-speed camera. The liquid sheet and droplets breakup mechanism, liquid sheet breakup length, width, droplet diameter and velocity, were studied under different jet velocity and horizontal impinging distance and perpendicular impinging distance. The results revealed that with increasing jet velocity from 1.42 m/s to 6.61 m/ s, different breakup modes were observed: closed-rim mode, open-rim mode, rimless mode, and wave or ligament mode. At low jet velocities, increasing impinging distance delayed the development of breakup mode. Based on experimental observations, the sheet breakup mechanism is categorized into two main regimes with four subregimes. Droplet breakup occurs in two stages: growth and necking, however, at high jet velocities complete breakup was achieved. Increasing jet velocity led to an increase in liquid sheet breakup length, width, and droplet velocity but a decrease in droplet diameter. Conversely, increasing impinging distance resulted in a decrease in liquid sheet breakup width and droplet radial velocity but an increase in droplet diameter. The effect of perpendicular impinging distance on axial velocity and breakup length was found to be more significant than that of horizontal impinging distance due to the effect of perpendicular nozzle. The findings indicate that the perpendicular jet greatly enhances atomization. This study provides a theoretical basis for designing and optimizing FTIJs.