Publication Date

2025

Document Type

Dissertation/Thesis

First Advisor

Monsu Lee, Eric

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Mechanical Engineering

Abstract

With industrialization and the increasing use of microplastics and nanoparticle-based products, the concentration of fine particulate matter (PM2.5) in the biosphere has increased due to the disposal of manufacturing waste and expired parts. If inhaled, PM2.5 can have detrimental health effects, as these particles can travel deep into the lungs and even penetrate blood vessels. Conventional fabric filters used for indoor air quality control have drawbacks, including the need for periodic filter replacement and a high-pressure drop across the filter over time, which leads to increased power consumption. In power plants, electrostatic precipitators (ESPs) are primarily used to collect fly ash, achieving a mass collection efficiency of over 99%. However, for submicrometer particles, the collection efficiency drops below 70%, primarily due to their small size, which results in a low particle charging rate experienced by these particles. The movement of particles in ESPs depends on factors such as the electric field, ion density, inlet flow velocity, particle properties, electrode geometry, and electrohydrodynamic (EHD) flow. Higher collection efficiency of fine particles can be achieved by promoting collisions and particle agglomeration in multi- stage ESPs, which are spacious and complex in design. During corona discharge, large-scale EHD vortexes can be induced in single-stage ESPs, considering the discontinuity in current density, which modifies the turbulent boundary layer and changes the collective behavior of the submicrometer particles. This large-scale EHD vortex has not been extensively characterized. The flow has been studied only with a 2-D axisymmetric model and has not been experimentally confirmed (Lee, 2024). This study aims to experimentally (1) verify the existence of large-scale EHD vortex flow, (2) assess its ability to confine fine particles, and (3) evaluate its contribution to agglomeration, which can be achieved by developing a wire-to-plate ESP to trap aerosol particles. By precisely tuning the EHD numbers, EHD vortex flow fields can be obtained depending on the discharge voltage in the ESP. Large- scale EHD vortex flow at three different EHD numbers is characterized using Particle Image Velocimetry (PIV) seeded with DEHS particles (mean d_p size 1μm). At EHD# 1.36 × 10^5, 1.68×10^5, and 2.03×10^5, a pair of stable counter-rotating vortexes was observed near the edge of the electrodes, trapping the DEHS particles for particle agglomeration. For qualitative analysis of the flow field for particle agglomeration, the PIV images of the vortex domain are analyzed to obtain fluid flow dynamics in the inter-electrode space, which include the velocity flow field and the vorticity flow field. For quantitative analysis of agglomeration, 6% of the total flow was sampled from the center of the vortex, which had comparatively higher vorticity. Particle sizes were analyzed using a PM sensor based on light-scattering principles to determine the particle size distribution. The findings from both analyses suggest that at EHD# = 2.03 × 10^5, it resulted in the highest trapping potential and a maximum rate of particle agglomeration.

Extent

144 pages

Language

en

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

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