Diagnostic Study of Pulsed Power Solution Plasmas
Date Issued
2012
Date
2012
Author(s)
Hsieh, An-Hsuan
Abstract
In this study, the pulsed voltage is generated by a pulsing unit and used to sustain plasmas in NaNO3 electrolytic solution. The pulsed power solution plasma system owns the better stability and cycle to cycle reproducibility and is capable of control the complex bubble dynamics, which is advantage of the further investigation and understanding of the solution system.
These experimental investigations include two parts: Firstly, plasmas in NaNO3 solutions sustained by pulsed power with Ton = 10 to 500 μs is studied. With an applied voltage equal or lower than 100 V, the bubble mode is observed. In this mode, bubbles hundreds μm in diameter are formed and detached continuously at the electrode surface because of the buoyant force. When the applied voltage increases to 125 V, the bubble to jetting transition occurs. The examination of various conditions shows that the transition occurs when the power and energy inputs simultaneously exceed critical values, 4.4×10-3 ± 6×10-4 J and 45 ± 5 W, respectively, within Ton are required. Given the electrode surface area, this critical power is equivalent to a heat flux of 229 ± 25 MW/m2, which is close to the heat flux required, 223 MW/m2, for the occurrence of explosive vaporization reported in the literature. Such an observation strongly supports the hypothesis that the bubble to jetting transition is induced by the electrothermal effect. Secondly, the decolorization and degradation of Acid Orange 7 (AO7), an anionic monoazo dye, and the detection of OH radicals formed with disodium salt of terephthalic acid (NaTA), a well-known OH radicals molecular probe, by plasmas in NaNO3 solutions sustained by pulsed power with Ton = 0.1 ~ 1 ms is investigated experimentally. In the study of decomposition of AO7, the kinetic analysis of the decolorization and degradation of AO7 show a pseudo-first-order reaction to AO7 concentration. The rate constants of decomposition of AO7 are a function of Ton. The study of OH radical detection includes using NaTA and the highly fluorescent property of the resulting 2-hydroxyterephthalic acid (HTA) to measure the OH radical. The production rate is related to the OH radical concentration as a function of Ton, which shows the similar tendency of the decomposition of AO7 as Ton increases. The combination of the above results gives the directly linear relationship between the decomposition rate of AO7 and the concentration of OH radical in solutions.
Subjects
solution plasmas
pulsed power
plasma diagnostics
dye degradation
Acid Orange 7 (AO7)
advanced oxidation processe
hydroxyl radicals
NaTA
kinetic model
Type
thesis
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