ID 403

Charged Liquid Jet Dynamics of a Dielectric Fluid

 

Abstract:

Atomization of a dielectric micro-jet is achieved via an electrohydrodynamic charge injection process. The atomizer is comprised of a grounded nozzle housing (ground electrode) and an internal probe (high voltage electrode) that is concentric with the emitting orifice. The internal probe is held at electric potentials that are as large as 15 kV. A pressurized reservoir drives a dielectric fluid at a desired flow rate through the orifice, ranging from 100 to 500 micrometers in diameter. The fluid fills the cavity between the electrodes as it passes through the atomizer, impeding the transport of electrons. This process imparts charge into the flowing fluid. Upon exiting the orifice, the emitted charged jet deforms via a bending instability that is qualitatively similar to the behavior observed in the electrospinning of fibers. We observed bulging regions, or nodes, of highly charged fluid forming along the bent, rotating jet. These nodes separate from the jet and form highly charged droplets that emit satellite droplets through a charge fission process. We also observed a critical threshold that governs the transition from a whipping mode into a ramified mode for the jet. This threshold is a function of non-dimensional groups pertaining to phenomena occurring inside the nozzle. Our study focuses on the jet dynamics, its break up, and the governing physics dictating the transition from the whipping to the ramified mode. This research is supported by the American Chemical Society Petroleum Research Fund.