Numerical and experimental studies of collection efficiency of an ion electrostatic collector for a mini-volume electrical PM detector

Abstract

The experimental efficiency was numerically and experimentally studied for collecting negative and positive ions in a coaxial cylindrical electrostatic collector for a mini-volume electrical PM detector. The commercial computational fluid dynamics software package COMSOL Multiphysics™ was used to predict the behaviors of the flow and electric fields as well as the particle trajectories in the collecting zone of the ion collector. In the experiment, the ions were generated by a corona-needle ionizer with concentrations greater than 10 13 ions/m 3 , the positively and negatively applied voltages at the inner electrode ranged from 0 to 45 V and the ion flow rates ranged from 1 to 5 L/min. For these ion flow rates, 1e5 L/min, the ion precipitates due to space charge and diffusion effects ranged from 92 to 97 % for positive ions and 91 e97 % for negative ions. The total collection efficiency of the collector increased to 100% at collection voltages larger than 5, 20 and 40 V respectively for the ion flow rates of 1, 3 and 5 L/min for both positive and negative ions. Numerical calculation results of the ion trajectory in the collecting zone of the collector; showed good agreement with the experimental results of the total collection efficiency and can be used to support the bettering of designing in order to refine an ion collector after the charger or ionizer in a mini-volume electrical aerosol detector. Finally, this shows that this ion collector was proven to be particularly useful as an electrostatic collector for positive and negative ions after the charger or ionizer in a mini-volume electrical aerosol detector.