Experimental study on droplet breakup and droplet particles diffusion of a pressure nozzle based on PIV

The x-swirl nozzles has been widely used in the field of spray technology for dust reduction. In this study, experimental studies on the droplet breakup and droplet particles diffusion of X-swirl nozzles by particle image velocimetry (PIV). Based on the experimental results, the velocity fields at five different water supply pressures were compared, and 6 MPa was chosen as the water supply pressure to study droplet breakup and droplet particles diffusion. The results show that, turbulence can change the trajectory of droplets and have an important impact on the atomization process. The variation law of turbulence intensity in axial and radial directions is revealed. The turbulence intensity (I) in the spray field axial direction continuously decreased as the distance increased and had an overall exponential relationship. I within 2.5 mm in the radial direction of the spray field's center rapidly decreased, but the downward trend slightly decelerated in the area exceeding 2.5 mm. Combined with the parameters of strain rate (S) and vorticity (X), the comparative analysis is carried out. When the gas and liquid are fully mixed, the turbulence intensity increases rapidly. This promotes the growth, deformation and breakup of droplets, and affects the diffusion of droplets. Through the probability density function, it is revealed that droplet breakup mainly occurs in the range of 0-4 mm near strong turbulence. The droplet size at different locations was measured by Phase Doppler Interferometer (PDI), which revealed the mechanism of turbulent flow on the droplet size. In the range of 0-300 mm, the droplets with larger initial particle size and veloc-ity gradually evolve into droplets with small particle size, small velocity and large number over time. But in the 300-450 mm range, the turbulent flow's effect on the breakup gradually decreased with the dro-plet movement time. Most of the droplets have finished breaking. Due to coalescence between small dro-plets, the particle sizes tended to slowly increase. (c) 2022 Published by Elsevier Ltd.

Automated summary

This study experimentally investigated the droplet breakup and droplet particles diffusion of X-swirl nozzles and revealed the impact of turbulence on the atomization process. The experimental results showed that turbulence can change the trajectory of droplets and have a significant effect on droplet breakup.