Charge distributions of aerosol dioctyl sebacate particles charged in a dielectric barrier discharger

The collection efficiencies of submicron aerosol particles using a two-stage, dielectric barrier discharge (DBD) type electrostatic precipitator have been reported previously [Byeon et al. (2006). Collection of submicron particles by an electrostatic precipitator using a dielectric barrier discharge. Journal of Aerosol Science, 37, 1618-1628]. In this paper, the charge distributions of aerosol dioctyl sebacate (DOS) particles, which had a mobility equivalent diameter of 118, 175, and 241 nm and were charged in a DBD charger, were examined using a tandem differential mobility analyzer (TDMA) system at applied voltages of 9-11 kV and frequencies of 60-120 Hz. The mean number of elementary charges for positively or negatively charged particles increased slightly with increasing applied voltage or frequency. However, the number of elementary charges increased significantly with increasing particle size. At any applied voltage and frequency, the charge distributions of these particles of these sizes indicated asymmetric bipolar charging. The positive-to-negative charge ratios were 10.4, 4.7, and 3.0 for particle sizes of 118, 175, and 241 nm, respectively, at a DBD voltage and frequency was 9 kV and 60 Hz, respectively. Fluorometric analysis showed that average positive-to-negative charge ratios were 11.5, 4.9, and 3.7 for particle sizes of 118, 175, and 241 nm, which agrees well with the TDMA results. Further fluorometric analyses with larger particles (514 and 710 nm) and higher frequencies (1 and 2 kHz) showed that the positive-to-negative charge ratio reached almost unity with increasing particle size or frequency.