This study aims to produce bipolar ions with Dielectric Barrier Discharge (DBD) in air, at atmospheric pressure to charge aerosol (solid or liquid particles suspended in a gas).

To prevent from discharge destabilization with the collection of aerosol on the dielectric surface, the strategy is to charge aerosol in post-DBD. The ions density of the usual radioactive neutralizer is in order of 1013 m-3[1]. Ion currents in Post-DBD reach hundreds of pA for flow rates higher than 1 L/min for both polarities (∼1012 ions.m‑3) [2]. So, ion densities have to be increased by at least one order of magnitude to charge initially neutral aerosol with concentration up to 1013 m3.

The first part is focused on the effect of electro‑hydro-thermodynamics processes (controlled by applied voltage, gas velocity in the gap, gas temperature and geometry) on the properties of the discharge (filaments mean charge and mean energy, total number of transferred charge in the gap, input power).

To control the discharge, the mean charge transferred by filaments in the external circuit, the charge transferred during a half-period, the power and the electrode temperature are measured versus the applied voltage (peak-to-peak voltage and frequency) and the flow rates. At the quasi steady state, the mean gas temperature in the discharge is evaluated from electrode temperature measurement [3]. The input power and the correcting factor of the current (to convert the electric parameters in the external circuit to these parameters in gas) are determined by the Lissajous figure [4]. The transferred charge by a filament in the gas is determined by the product of the measured charge in the external circuit and the correcting factor. The mean energy per filament is calculated with the product of the mean measured charge by filaments by a “conversion” voltage. This “conversion” voltage is the ratio of the mean energy by period on the total charge transferred by period.

In The second part, post-DBD ions densities taking into account the losses of ions between the production and the measurements are presented versus the electro-thermal characteristics of DBD. The positive and negative ion currents are measured in post-DBD. The ions extraction and transport depend on diffusion and electrostatic transport. The post-DBD ions current is measured as function of length from discharge and flow-rates for different discharge conditions. Ion densities and losses are reported regarding discharge properties, post-discharge geometry and transit time before measurement.

References

[1] Modesto-Lopez L. B. , Kettleson E. , M. Biswas P. , Journal of electrostatics (2011) , 69 , 357-364

[2] Bourgeois E. , Jidenko N. , Alonso M. , Borra J.P. , J. Phys. D: Appl. Phys. ( 2009), 42 , 205202 (9 pp)

[3] Jidenko N., Bourgeois E. and Borra J.-P., J. Phys. D: Appl. Phys. (2010), 43, 295203.

[4] Pipa A. V. , Hoder T. K. , Schmidt J. M. , Brandenburg R. , Review of scientific instrument (2012) , 83, 75111