Experimental investigation on the deformation and breakup of charged droplets in dielectric liquid medium

Electrical manipulation of droplets has attracted extensive research interests owing to its advantageous of implementation in various fields, such as spacecraft propulsion, mass-spectrometry and targeted drug delivery in blood. In this paper, the deformation and breakup characteristics of charged droplets in dielectric liquid were controlled with a needle-plane electrode configuration in the presence of electric field. High-speed photography was utilized to capture the charged ethanol droplet deformation and breakup process near the nozzle. Four pioneering droplet breakup behaviors of the single regime, swing regime, branch regime and sheet regime were achieved successfully by manipulating electric field. The instructive droplet breakup phase diagram was illustrated based on various applied voltages and flow rates. Besides, the effect of electric field on droplet size distribution, breakup length and cone angle in various regimes was quantitatively discussed. It is found that increasing applied voltage leads to the decrease of droplet dimensions and the droplet size distribution follows the universal scaling law in single and swing regimes. Moreover, the breakup length and cone angle are evidently associated with droplet breakup regimes. The breakup cone angle decreases with increasing voltage in all regimes while the breakup length fluctuates in various regimes. (C) 2019 Elsevier Ltd. All rights reserved.