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

Long-term exposure to PM2.5, which is responsible for four million cardiovascular-related deaths worldwide, is a major concern as people spend 90% of their time indoors. Fabric filters have been commonly utilized for particle pollution control in indoor settings. However, the maintenance cost of fabric filters is relatively high, as particle accumulation on filters can lead to higher pressure drops (45 ∼ 300 Pa) and energy consumption, as well as the growth of biological organisms and the generation of airborne pathogens. An electrostatic precipitator (ESP) is filterless and widely used in the electric power industry for collecting coal fly ash. ESPs can achieve more than 99% of particle collection efficiency with minimal pressure drop (∼ 4 Pa) but also suffer from low collection of PM2.5 and ozone generation. Therefore, ongoing research is to modernize ESPs by considering various agglomeration techniques to improve PM2.5 collections. Earlier work centered on electrostatic agglomeration, requiring bipolar particle charging and a separate stage for collecting enlarged particles, which increased the system’s costs and complexity. The theory of path coalescence postulates that random forces fluctuating in space and time can cause particle trajectories to converge. The present study advances this theory in an electrohydrodynamic (EHD) flow through electrode modification in a longitudinal wire-plate ESP. The objective is to generate a sinusoidal EHD flow by an altered electric field for electrostatic agglomeration between unipolar-charged Di-Ethyl-Hexyl-Sebacat (DEHS) droplets (d_p = 1µm). Three case studies were conducted with EHD numbers ranging from 5.1 to 6.2, while the DEHS particle concentration at the inlet was 4.5×10^5 #/Liter. A Particle Image Velocimetry (PIV) enabled by a double pulse laser (532 nm) and a sCMOS camera was utilized to study path coalescence and agglomeration. The PIV images indicated the generation of sinusoidal flow under the influence of the altered electric field at discharge voltages varied between -14 kV and -17 kV. The streamline plots showed the onset of path coalescence. A pixel analysis in MATLAB further proved particle agglomeration between DEHS droplets, focusing on three locations along the merged particle trajectories. The equivalent pixel number of a DEHS droplet without particle charging was equal to or less than 350 pixels. The plots of the histogram, cumulative distribution function (CDF), and particle growth factor indicated the presence of larger droplets with sizes between 350 and 1500 pixels. The findings serve as the first step toward developing a novel electrostatic bioaerosol agglomerator.

Extent

131 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.

Media Type

Text

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