Numerical investigation of ionic conductor liquid charging at low to high voltages

Abstract

A numerical modeling of electrification and ion transport in ionic conductor liquids (oils) is conducted while allowing for the Frumkin-Butler-Volmer kinetics responsible for the ion transfer at metal electrode surfaces. The numerically predicted near-electrode polarized layer is validated against a boundary layer analytical solution for low voltages also developed in this paper. Another benchmark related to microchannels with dielectric walls with a non-zero ζ-potential is used to validate the implementation of the Coulombic body force responsible for the electro-osmotic flow. Finally, the case of an electrohydrodynamic flow in a microchannel (a model for the flow and charging inside an electrostatic atomizer) with two metal electrodes of opposite polarity attached is considered aiming at the prediction of the resulting net charge at the channel exit. The charging electrodes occupy only a fraction of the channel walls, which are otherwise insulated. It is shown that the considered channel length does not play a role in determining the available net charge achieved at the exit. Indeed, the value of the spray current practically does not vary along the exit section of the channel (behind the electrode part), which means that irrespective of the exit location, the spray current would be the same. Moreover, it is shown that in the present case, the role of the Smoluchowski slip near the electrodes is negligibly small compared to the viscous scraping of the polarized layer under any realistic values of the imposed longitudinal electric field.

Electrically driven toroidal Moffatt vortices: experimental observations

“…All surfaces are subjected to no-slip boundary conditions, and the liquid is initially at rest. There are numerous methodologies available to pose the boundary condition for the electric current at the electrode surface (Suh 2012), ranging from a fixed current density to variation proportional to the electric field, or associating it with the bulk dissociation reactions and faradaic reaction at the surface (Kashir et al 2019). For this simulation, a constant charge density is applied at the electrode surface at those locations where the electric field strength at the surface is greater than or equal to 30 % of the peak electric field strength (located at the tip of the electrode).…”

Electrostatically Sprayed Nanostructured Electrodes for Energy Conversion and Storage Devices

“…[14,[20][21][22][23][24] A possible mechanism of net charge formation in the liquid at the nozzle is associated with electron loss or electron injection at the metal electrodes, i.e., with Faradaic reactions neutralizing or forming ions. [25][26][27] Accordingly, electrospraying can be subdivided into four different stages: 1) transition from droplet sustained at the nozzle tip to a tiny jet issued from the tip of the modified Taylor cone; 2) breakup of the electrified jet issued from the tip of the modified Taylor cone (the cone-jet mode); 3) alternatively, at a relatively high rate of pumping, the jet can be issued from the nozzle due a pressure drop rather than due to the electric pulling, but can still be electrified, as in the work of Rayleigh, and its breakup can be influenced by electric forces; 4) secondary breakup of the electrified droplets. We next briefly consider these stages one-by-one.…”

“…[ 14,20–24 ] A possible mechanism of net charge formation in the liquid at the nozzle is associated with electron loss or electron injection at the metal electrodes, i.e., with Faradaic reactions neutralizing or forming ions. [ 25–27 ]…”

Slow Discharge Theory and Calculation of the Potential Drop across the Compact Layer at High Electrode Voltages

“…The ionic conductor liquid in contact with metallic electrodes sustains an electric current due to the faradaic reactions. This model has been built on the OpenFOAM computational platform and validated previously using several benchmark problems . The model is composed of the ionic transport equations and Poisson’s equation for the electric potential: …”

“…This model has been built on the OpenFOAM computational platform and validated previously using several benchmark problems. 31 The model is composed of the ionic transport equations and Poisson's equation for the electric potential:…”