cus at the outlet of the capillary, through the apex of which An experimental investigation was performed on electrosprays a fine liquid ligament is ejected. The liquid ligament breaks of low electric conductivity liquids (heptane with different up farther downstream to disperse into a spray of droplets amounts of an antistatic additive) that were operated in the conewhich often shows a remarkably narrow size distribution jet mode. The effects of liquid flow rate, applied voltage, and liquid . This mode of spray operation is usually referred to electric conductivity on droplet size and spray monodispersity as ''cone-jet mode'' (4) in view of the liquid meniscus were systematically investigated. The droplet size was found to be morphology. The reason for the monodispersity of the conedominantly controlled by the liquid flow rate and secondarily by jet electrospray is that axisymmetric surface wave instabilithe applied voltage. It showed no dependence on capillary size.
ties dominate the liquid ligament breakup, which results in For a given liquid, stable and monodisperse electrosprays could be established only within certain ranges of liquid flow rates and a constant ratio between primary droplet diameter and ligaapplied voltages, that defined a cone-jet domain. This domain was ment diameter. For liquids with small viscosity, the ratio affected by the electric conductivity of the liquid. As the liquid was measured at about 1.89 (1, 4-6), consistent with the electric conductivity increased, the domain shifted toward smaller prediction of Rayleigh's capillary instability theory (7). Any flow rates which implies that smaller droplets were generated in satellite produced during breakup is confined by electrostatthe spray. An increase in the capillary diameter caused a narics as well as inertia to the spray periphery and can be easily rowing of this domain. Outside the cone-jet domain, electrosprays skimmed off (1).
were unstable and polydisperse with different instability patterns
The spray formed by this atomization technique has several that depended on the applied voltage and the liquid flow rate.
unique features. Since droplets are highly charged, the Cou-Experiments also showed that the droplet size and the spray monolombic repulsion causes them to self-disperse, which prevents dispersity were independent of the electrode configuration, as long their coalescence and eases their penetration into the host gas as the electrospray was operated at the onset voltage condition, that is defined as the minimum voltage at which the cone-jet mode medium. In contrast to aerodynamic atomization processes, was established. By using dimensional analysis the controlling liquid atomization and gas flow processes are relatively unvariables were combined into a few dimensionless groups and an coupled, which offers additional flexibility in the optimization empirical fit was derived and was shown to correlate well all the of mixing. Because the trajectory of a charged droplet can in experimental data.