Performance evaluation of a miniature plate Electrostatic Aerosol Analyzer (mini-plate EAA)

Abstract

To enable the tempo-spatial distribution monitoring/measurement of ultrafine particles, a cost-effective and miniature plate Electrostatic Aerosol Analyzer (mini-plate EAA) has been designed and characterized in this study for the use in electrical-mobility-based aerosol sizers. The prototype consists of two metal plates, installed in parallel in an insulation block, to establish the zone for particle classification. To minimize the effect of side wall in the classification zone, the length of aerosol entrance slit opening is half of the width of the classification zone. The performance of the mini-plate EAA, i.e., its transmission efficiency and transfer function, were experimentally evaluated for particles with the sizes ranging from 20 to 120nm. It is shown that the transmission efficiency of singly charged particles was nearly 100% in the sizes larger than 60nm and was dependent on the aerosol-to-sheath flow rate ratio for particles with the sizes less than 60nm when operated at the total flow rate of 3.0lpm. The particle penetration curves as a function of applied voltages were obtained for various combinations of aerosol and sheath flow rates. A modified 2-D model was further proposed to better calculate the cutoff voltage at the 50% penetration. The experimental transfer functions of the mini-plate EAA under the conditions of various aerosol-to-sheath flow rate ratios and at 3.0lpm sheath flow were given in this study.