Examination of after-charging effects downstream of an aerosol neutralizer

Abstract

Depending on the concentration of aerosol particles and the Nt product (ion number concentration ×residence time), a relatively high concentration of free unattached ions may still survive long after an aerosol has left the neutralizer. The possible existence of after-charging effects downwind of an aerosol neutralizer caused by these residual free ions has been examined. Experiments have been carried out using a commercially available neutralizer (TSI model 3077), two different levels of aerosol concentration, varying lengths of a tube connected to the neutralizer outlet, and different mean aerosol residence times in the neutralizer. The reference charged aerosol leaving the ionizer was mixed with a foreign uncharged aerosol. Although the foreign particles acquire electric charges by attachment of the residual free ions, the charge distribution of the reference aerosol remains unmodified provided its mean residence time in the neutralizer is long enough for it to attain a steady-state charge distribution.