Investigating the effect of electrical conductivity on electrospray modes

This study investigated experimentally the effect of electrical conductivity on electro-hydrodynamic (EHD) modes in the electrospray process. The geometric shape of the micro-droplets having different electrical conductivity was studied. For this purpose, three fluids, including acetic acid, ethanol, and toluene, were selected as the representation of three different fluid classifications in terms of electrical conductivity. The difference in conductivity of these fluids can be characterized by α denoting the ratio of electrical relaxation time to the characteristic hydrodynamic time. The experiments showed that the increase in α did not significantly affect the transfer of the EHD modes. In addition, analytical and graphical investigations showed why ethanol as a leaky dielectric fluid produced lower droplet diameters in comparison with acetic acid as a conductive fluid at highest electrical capillary numbers. Also, a pulsation mode was monitored in the experiments related to toluene as a dielectric fluid. Finally, an equation was presented for calculating the dimensionless diameters of ethanol droplets and acetic acid using non-dimensional numbers derived from the experimental data.