SIMULATION ON MOTION OF A GROUP OF CHARGED DROPLETS IN AN ELECTROSTATIC SPRAY PROCESS

Abstract

Considering the droplet size and charge distributions, breakup length of the charged jet, electrical interaction between droplets, and especially, the variation of droplet number with time, the two-dimensional motion is simulated for a group of charged droplets continuously generated in an electrostatic spray process. The droplet spatial distributions obtained from simulation and from experiments are basically consistent. The simulation results show that the larger droplets move mainly in the central area of spray, while the smaller ones have a trend moving toward the edge area of spray. The results also show that the effect of the electrical interaction force between droplets on droplet motion is significant, and it cannot be ignored for cases with a fairly long distance from the capillary exit. In the area near the capillary exit, the electrical interaction force is very large and its direction also randomly changes during the droplet migration process. This leads to a significant fluctuation in the droplet velocity curve. With the increase of distance from the capillary exit, the electrical interaction force becomes small and relatively regular. This causes the droplet velocity and trajectory curves to gradually become smooth. In comparison, the curves of velocity and trajectory for large droplets are smoother than those for small droplets. In addition, droplet concentration, axial and radial velocity distributions, as well as the forces on the droplet are also obtained, and some local behaviors of droplet motion are revealed.