Experimental investigation of droplet formation mechanisms by electrostatic dispersion in a liquid-liquid system

Droplets having high uniformity and a widely controllable size range (from mm to μm) were obtained by means of electrostatic dispersion in an oil-in-water system, as reported previously by the authors. In liquid-in-gas systems, many studies reported that the electrostatic force acting on the liquid due to the surface charge seemed to be the main factor affecting the atomization. However, using distilled water as a continuous-phase liquid causes the theoretical analysis to be very difficult because distilled water has high conductivity and permittivity. Therefore, in the present study, experimental work is carried out on dispersion mechanisms in an oil-in-water system. The main factor affecting the atomization is considered to be electrohydrodynamic flow of continuous-phase liquid (distilled water) around the capillary nozzle tip. The repulsive force between the nozzle tip and the charged liquid meniscus is also considered to have a small effect. The amount of electric charge on the dispersed-phase liquid (kerosene) is considered to be negligible because of the very short relaxation time of the surrounding continuous-phase liquid. It is suggested that the droplet size and frequency distribution can be controlled by adjusting the operating conditions (applied voltage) and design parameters (nozzle shape)