Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Electrical and Computer Engineering

Supervisor

Kazimierz Adamiak and G. S. Peter Castle

Abstract

This thesis presents the results of a three-dimensional simulation of the entire precipitation process inside a single-electrode one-stage electrostatic precipitator (ESP). The model was designed to predict the motion of ions, gas and solid particles. The precipitator consists of two parallel grounded collecting plates with a corona electrode mounted at the center, parallel to the plates and excited with a high dc voltage. The complex mutual interaction between the three coexisting phenomena of electrostatic field, fluid dynamics and the particulate transport, which affect the ESP process, were taken into account in all the simulations. The electrostatic field and ionic space charge density due to corona discharge were computed by numerically solving Poisson and current continuity equations, using a hybrid Finite Element (FEM) - Flux Corrected Transport (FCT) method. The detailed numerical approach and simulation procedure is discussed and applied throughout the thesis. Calculations of the gas flow were carried out by solving the Reynolds-averaged Navier-Stokes equations using the commercial FLUENT 6.2 software, which is based on the Finite Volume Method (FVM). The turbulence effect was included by using the k-ε model included in FLUENT. An additional source term was added to the gas flow equation to include the effect of the electric field, obtained by solving a coupled system of the electric field and charge transport equations, using the User-Defined-Function (UDF) feature of FLUENT. The particle phase was simulated using a Lagrangian-type Discrete Random Walk (DRW) model, where a large number of particles charged by combined field and diffusion charging mechanisms was traced with their motion affected by electrostatic and aerodynamic forces in turbulent flow using the Discrete Phase Model (DPM) and programming UDFs in FLUENT. The airflow patterns under the influence of electrohydrodynamic (EHD) secondary flow and external flows, particle charging and deposition along the channel, and ESP performance in removal of submicron particulates were compared for smooth and spiked discharge electrode configurations in the parallel plate precipitator assuming various particle concentrations at the inlet. Finally, a laboratory scale wire-cylinder ESP to collect conductive submicron diesel particles was modeled. The influence of different inlet gas velocities and excitation voltages on the particle migration velocity and precipitation performance were investigated. In some cases, the simulation results were compared with the existing experimental data published in literature.


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