Designing Multi-Layer electret filters via numerical simulation

Abstract

The deposition of neutral and charged particles inside an electrostatically charged filter can affect its performance by decreasing its ability to capture additional particles and by increasing its pressure drop. The particle-loaded behavior of a composite filter comprised of three fibrous layers is studied in this paper using a macroscale simulation approach. Each of these fibrous layers were assumed to have fibers with the same amount of charge but different charge polarities of only unipolar positive, only unipolar negative, or only bipolar. The charged layers were stacked on top of one another in three different configurations with respect to the flow direction and their filtration efficiency and pressure drop were compared during particle loading with neutralized particles (having the Boltzmann equilibrium charge distribution), singly-charged particles, and neutral particles. Our simulations revealed that placing the bipolarly-charged layer downstream of the unipolarly charged layers helps to lower the negative impact of particle deposition on pressure drop and filtration efficiency of the resulting composite filter. This study introduces a design tool which can be used to optimize the configuration of a composite filter for enhanced particle capture efficiency and reduced pressure drop increase.