[CCoE Notice] Cullen College Dissertation Defense Announcement - Dong Zhang

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[Dissertation Defense Announcement at the Cullen College of Engineering]

Numerical Simulation of an Atmospheric Pressure Argon-Oxygen Dielectric Barrier Discharge and Comparison to Experimental Data



Dong Zhang

November 30, 2022;  3:00 PM – 5:00 PM (CST)

Team Link: https://urldefense.com/v3/__https://teams.microsoft.com/l/meetup-join/19*3ameeting_NjVlY2YwMmQtMTMyNC00ZTQ5LTljOTItMWUyYzgxNzkxYmZl*40thread.v2/0?context=*7b*22Tid*22*3a*22170bbabd-a2f0-4c90-ad4b-0e8f0f0c4259*22*2c*22Oid*22*3a*2278308efa-b162-41ff-8cad-423fdfc83bb8*22*7d__;JSUlJSUlJSUlJSUlJSUl!!LkSTlj0I!CRx0809VIjE9EiNbOcOyHt5aw5fcFt8dwVL1ksgGP9fNmNh3B-zDDCYhOQZQdgYaP6sqSAp6BOdrBN7DKXZCXPi3F-k$ <https://urldefense.com/v3/__https:/teams.microsoft.com/l/meetup-join/19*3ameeting_NjVlY2YwMmQtMTMyNC00ZTQ5LTljOTItMWUyYzgxNzkxYmZl*40thread.v2/0?context=*7b*22Tid*22*3a*22170bbabd-a2f0-4c90-ad4b-0e8f0f0c4259*22*2c*22Oid*22*3a*2278308efa-b162-41ff-8cad-423fdfc83bb8*22*7d__;JSUlJSUlJSUlJSUlJSUl!!LkSTlj0I!CHCuI5bcxGDaRysGNcjXr7AMAuBCcQgw6J4reetB0lFwbhoW6hk5IQJrk9PHhfu42F2X92S2Npqk0Q--pU2tQ5o3oFdd$>





Committee Chair:
Demetre Economou, PhD and Vincent Donnelly, PhD

Committee Members:
Michael Nikolaou, Ph.D. | Paul Ruchhoeft, Ph.D. | JC Wolfe, Ph.D.

Abstract

       Atmospheric pressure dielectric barrier discharge (DBD), a self-sustaining capacitively coupled discharge, has attracted much attention due to its merits, including simpler design without vacuum pumps, versatile working conditions, and reproducible generation of volumetric plasma.

       Numerical simulation, based on a fluid model, of low-temperature (cold) atmospheric pressure Ar and Ar/0.1% O2 dielectric barrier discharges was performed. For both pure argon and Ar/0.1% O2 DBDs, as the applied peak voltage was increased, the discharge transitioned from single-peak, to multi-peak, and finally to continuous mode. Most ionization occurred inside the sheath, with the discharge running under γ-mode. For pure Ar DBDs, the space- and time-averaged electron temperature dropped from 1.40 eV to 1.18 eV initially, then remained almost constant at 1.20 eV as the voltage was varied. The electron, argon ion, and argon metastable densities increased by 19.1, 2.93, and 8.26 times, respectively, for a change of the peak voltage from 0.75 kV to 1.5 kV to 3.0 kV. The number densities of all species increased with increasing applied voltage.

       To influence of tailored voltage waveforms, with harmonic number N ranging from N=1 to N= 4, on an atmospheric pressure Ar/0.1%O2 DBD, was studied for the first time. The time-averaged electron density was lower, and the electron temperature was almost constant at 1.5 eV, as N was increased. Meanwhile, increasing N led to increasing discharge asymmetry. The dominant mode of electron heating was Ohmic, with small contributions of ambipolar heating. Penning dissociation was a major reaction producing O-atoms in the atmospheric pressure cold plasma operating in γ-mode. The number densities of electrons, positive ions, O-atoms, O3 and Ar metastables, all increased as the harmonic number N was increased.

       Two-dimensional cylindrically symmetric (r, z) fluid modeling of the downstream effluent of atmospheric pressure Ar/0.6% O2 dielectric barrier discharge was conducted. The measured O-atom density decreased monotonically, and the ozone density exhibited a maximum, as a function of position downstream of the discharge. The simulated number density of O-atoms and ozone on-axis showed the same trends as the experiment.

       A further comparison was conducted between experiment and simulation as a function of increasing % O2 (in the range 0-1.0 %) in the DBD. Both simulations and experiments showed an almost constant electron temperature, decreasing electron density, and a maximum (in the range of 0.3-0.5% O2) of the 844.6 nm optical emission intensity of O-toms as a function of increasing oxygen concentration in the feed gas.

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