Bulletin of the American Physical Society
64th Annual Gaseous Electronics Conference
Volume 56, Number 15
Monday–Friday, November 14–18, 2011; Salt Lake City, Utah
Session ET2: Green Plasmas |
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Chair: Ane Aanesland, Ecole Polytechnique Room: 255E |
Tuesday, November 15, 2011 2:00PM - 2:15PM |
ET2.00001: Air Purification Pavement Surface Coating by Atmospheric Pressure Cold Plasma Joe Westergreen, Patrick Pedrow, Shihui Shen, Bertram Jobson This study develops an atmospheric pressure cold plasma (APCP) reactor to produce activated radicals from precursor molecules, and to immobilize nano titanium dioxide (TiO$_{2})$ powder to substrate pavement materials. TiO$_{2}$ has photocatalytic properties and under UV light can be used to oxidize and remove volatile organic compounds (VOCs) and nitrogen oxides (NO$_{x})$ from the atmosphere. Although TiO$_{2}$ treated paving materials have great potential to improve air quality, current techniques to adhere TiO$_{2}$ to substrate materials are either not durable or reduce direct contact of TiO$_{2}$ with UV light, reducing the photocatalytic effect. To solve this technical difficulty, this study introduces APCP techniques to transportation engineering to coat TiO$_{2}$ to pavement. Preliminary results are promising and show that TiO$_{2}$ can be incorporated successfully into an APCP environment and can be immobilized at the surface of the asphalt substrate. The TiO$_{2}$ coated material with APCP shows the ability to reduce nitrogen oxides when exposed to UV light in an environmental chamber. The plasma reactor utilizes high voltage streamers as the plasma source. [Preview Abstract] |
Tuesday, November 15, 2011 2:15PM - 2:30PM |
ET2.00002: Laminar lean premixed methane/air combustion near the lean flammability limit using nanosecond repetitive pulsed discharge plasmas Moon Soo Bak, Hyungrok Do, Mark G. Mungal, Mark A. Cappelli Gas chromatographic and temperature measurements have been carried out to investigate the extent of premixed methane/air combustion with the application of nanosecond repetitive pulsed discharges around the lean flammability limit for laminar flows. The results show that the discharges lead to the complete combustion when the equivalence ratio is above 0.54, but when the ratio is below the limit, the combustion is quenched at the downstream flow. To investigate the kinetics in detail, 2-D simulations of plasma-induced combustion have been conducted for methane/air mixtures at below and above the lean flammability limit. The simulations reveal that methane is mostly combusted in the discharge region since the discharge repetition timescale is much shorter than the species diffusion and advection timescales, and so the discharge serves more as a heat and radical source rather than a small combustor, to flame hold near the lean flammability limit. [Preview Abstract] |
Tuesday, November 15, 2011 2:30PM - 2:45PM |
ET2.00003: Study of Microwave Plasma Enhanced Methane Flame at Atmospheric Pressure Nimisha Srivastava, Chuji Wang Non-thermal plasma assisted combustion can provide potential accommodation in improving fuel efficiency, contaminant reduction, faster ignition time, etc. A 2.45 GHz microwave (MW) plasma source was used with a premixed He/CH$_{4}$ gases to study the effect of MW power coupling and hence OH radical generation. UV pulsed laser cavity ringdown spectroscopy was employed to measure absolute number density of OH (A-X) (0-0) band in plasma enhanced flame. Emission species such as OH(A-X), N$_{2}$(C-B), N$_{2}^{+}$(B-X) and C$_{2}$ swan band were observed using optical emission spectroscopy. Depending on the mixing ratio of CH$_{4 }$and MW power, two kinds of CH$_{4}$ flames were obtained; (1) Flame with coupled MW energy but no pre-flame (flame and plasma interaction region); at high CH$_{4}$/He mixing ratios and low MW energies, detached flame were obtained with detaching gap depended on MW power. (2) Flame with visible pre-flame region: at low CH$_{4}$/He mixing ratios and high MW energies. In both the cases total flame volume increased with increase in MW energy. Compared to the flame, OH concentration was higher in the pre-flame. [Preview Abstract] |
Tuesday, November 15, 2011 2:45PM - 3:00PM |
ET2.00004: Plasma Gasification of Plastic Debris as a Method of the World Ocean Cleaning Philip Rutberg, Vadim Kuznetsov, Victor Popov, Alexander Bratsev, Alexander Ufimtsev, Sergey Shtengel, Irina Kumkova The paper deals with treatment of plastic debris, polluting the world ocean, in a plasma downdraft gasifier. The calculated data on syngas composition and its specific yield depending on raw material moisture and energy consumption are presented. The usability estimation of the produced syngas application for electricity generation and liquid fuel production is performed. [Preview Abstract] |
Tuesday, November 15, 2011 3:00PM - 3:15PM |
ET2.00005: STUDENT AWARD FINALIST: Study of Self-Absorbed Vacuum Ultraviolet Radiation during Pulsed Atmospheric Breakdown in Air George Laity, Andrew Fierro, Lynn Hatfield, Andreas Neuber This paper describes recent experiments to investigate the role of self-produced vacuum ultraviolet (VUV) radiation in the physics of pulsed atmospheric breakdown. A unique apparatus was constructed which enables the detailed exploration of VUV light in the range 115 -- 135 nm, which is emitted from breakdown between two point-point electrodes in an air environment at atmospheric pressure. Time-resolved diagnostics include VUV sensitive photomultipliers, intensified CCD imaging, optically isolated high voltage probes, and fast rise-time Rogowski current monitors. Temporally resolved spectroscopy from air breakdowns revealed VUV emission is released during the initial streamer phase before voltage collapse, with the majority of the emission lines identified from various atmospheric gases or surface impurities. Imaging of VUV radiation was performed which conserved the spatial emission profile, and distinct differences between nitrogen and oxygen VUV emission during onset of breakdown have been observed. Specifically, the self-absorption of HI, OI, and NI lines is addressed which elucidates the role of radiation transport during the photon-dominated streamer breakdown process. [Preview Abstract] |
Tuesday, November 15, 2011 3:15PM - 3:30PM |
ET2.00006: STUDENT AWARD FINALIST: Oxygen Pathways in Streamer Discharge for Transient Plasma Ignition S.J. Pendleton, S. Bowman, D. Singleton, J. Watrous, C. Carter, W. Lempert, M.A. Gundersen The use of streamers for the ignition of fuels, also known as transient plasma ignition (TPI), has been shown in a variety of engines to improve combustion through decreased ignition delay, increased lean burn capability and increased energy release relative to conventional spark ignition. The mechanisms behind these improvements, however, remain poorly understood. Temperature measurements by optical emission spectroscopy demonstrate that ignition by TPI is a nonthermal process, and thus is almost entirely dependent on the production and presence of electron impact-created active species in the discharge afterglow. Of particular interest are active oxygen species due to their relatively long lifetimes at high pressures and the pivotal role they play in combustion reactions. In order to elucidate the oxygen pathways, here we report the investigation of the temporal evolution of the populations of atomic oxygen and ozone by use of two-photon absorption laser induced fluorescence (TALIF) and UV absorption, respectively. Experimental results are presented and compared to kinetic modeling of the streamers. Future experiments are proposed to better understand the physics behind TPI. [Preview Abstract] |
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