AEROSOL CHARGERS USING IONIZING-RADIATION AND ELECTRIC-FIELD COLLINEAR TO FLOW - SIMULATION AND EXPERIMENT FOR FINE-PARTICLE CHARGING IN ELECTRONEGATIVE AIR AND ELECTROPOSITIVE NITROGEN

Performances of aerosol chargers employing alpha- or beta-radioactive sources to ionize carrier gas and using applied electric fields up to 4 kV/cm collinear to the aerosol flow have been investigated. The stud y was done for fine particles with radii from 0.027 to 1.5 mu m acquir ing an electrical charge in the non-uniform bipolar atmosphere of ions in air and of electrons and N-4(+) ions in nitrogen. The charging pro cess of aerosol particles of different concentrations has been analyze d by means of computer simulation, and the charge of the particles as they leave the charger has been calculated in two cases in which the v elocity vector of the aerosol stream is either parallel or anti-parall el to the strength vector of the applied electric field. A comparison has been made between calculations and experimental results of particl e charging in air, as well as between calculation results in air and u ltrapure nitrogen under the same conditions. Two types of chargers wit h the charging zones irradiated totally or partially by ionizing radia tion have been examined. The conditions for obtaining the maximum part icle charges both in air and nitrogen as well as the conditions for th e initial particle charge to be unaffected in air have been found. The experimental results of fine particle charging in air are in agreemen t with the theoretical calculations. (C) 1997 American Association for Aerosol Research.