Experimental Study on the Generation, Coulomb split and Movement Characteristics of Charged Droplets

Abstract

A discrete droplet's dynamic characteristics in another immiscible liquid under the actions of an electric field are widely encountered in many practical fields such as emulsification, transesterification, and spacecraft propulsion. An experimental study was carried out to investigate the generation, Coulomb split, and motion of charged methanol droplets with a typical nozzle-plate electrode apparatus by utilizing high-speed photography. Dynamic behavior of droplets with time-resolved characteristics at the ambient needle orifice was visualized at various electric field strengths and flow rates. The resulting phenomena were quantitatively analyzed with the image-processing software. The secondary Coulomb splitting mode of charged droplets, which could be divided into no-crushing deformation, one-side split, two-side split, and membrane breakup under the electric field, has been detailed. Besides, the average particle size and cumulative particle size distribution of broken droplets under different working conditions were obtained. When the electric field intensity reaches a specific range, the influence of electric field intensity and liquid flow rate on the size of broken droplets becomes negligible. Furthermore, the velocity magnitude of discrete droplets was discussed, and the cloud diagram of its velocity characteristics was presented. It could be found that increasing the electric field strength is more effective than the liquid flow rate in terms of enlarging the expansion angle of the atomized droplets and the velocity of the discrete phase droplets.