Influence of the voltage waveform’s shape and on-time duration on the dissolved ozone produced by a DBD bubble reactor

Abstract

In this study we examine both the effect of changing the applied voltage waveform shape and the modulation on-time on the amount of ozone dissolved within a liquid in a DBD bubble reactor. In this device, the discharge forms at the gas liquid interface allowing for effective transfer of the plasma effluent into the liquid. To produce different voltage waveforms, a multilevel inverter power supply capable of generating arbitrary waveforms without switching-on and switching-off transients has been used. Of the four waveforms used in the study (sinusoidal, sawtooth, square and short-pulse), the square waveform was found to be the most efficient at producing the highest ozone concentration for a fixed peak voltage and average power. To determine the effect of the modulation on-time, the number of cycles during the on-time were increased from 1 up to 1000, adjusting the off-time accordingly to maintain the same duty cycle. Shorter on-time periods were found to be more efficient. Experimental and computational results indicate that the time between subsequent discharges is critical for increased ozone generation efficacy, as this needs to be long enough for ozone produced in one discharge event to diffuse away from the discharge region before the next discharge event occurs, thereby avoiding its partial destruction in the plasma. This insight provides a valuable criterion for the optimization of DBD reactors used in novel biomedical, agricultural and environmental applications.

Graph Theory Applied to Plasma Chemical Reaction Engineering

“…Use of all the methods above, applied to an air plasma reaction set from [20], suggests that an optimal electron energy regime for ozone formation is a high amount of electron energy in the initial phase, and then no electron energy for the successive phases. This corresponds with evidence in the literature [10,24]. Use of the above methods also suggests that ozone destruction reactions occur much more rapidly at high electron energies, and at high temperatures (Fig.…”

“…In addition to the simulated results shown above, the energy level regime predicted by the O 3 targeted run of OCARINA also agrees with a recent study by Seri et al [24] of the effect of different waveforms on ozone generation. The study observed that the best efficacy of energy input for ozone generation was achieved with relatively large spaces between on times to prevent ozone destruction reactions from occurring.…”

Theoretical and experimental aspects of non-equilibrium plasmas in different regimes: fundamentals and selected applications

“…Corona discharges [158,159], Dielectric Barrier Discharges (DBDs) [160,161] and gliding arcs [162,163] are most common plasma typologies utilized. On the other hand, bubbling reactors flush air bubbles within the water, and the plasma is ignited within these bubbles or onto the separation surface waterbubble [164,165]. This configuration usually enhances exchange surface between air and water, maximizing the amount of charges and reactive species diluted within the liquid.…”

Microbubble-enhanced DBD plasma reactor: Design, characterisation and modelling

“…While a large number of RNS and ozone can be measured, some species such as H2O2, HNO2 and NO3 fell below the detection limit of FTIR or had overlapping peaks with other species; therefore the concentrations of those species were estimated from the computational results of Sakiyama et al, 2012. Concentrations of the reactive species achieved with a 30% duty cycle were then converted into partial pressures using the ideal gas law (see Table 2). Whilst a broad range of ROS and RNS species can be produced in atmospheric plasmas, the ratio between the two categories of species can be manipulated by changing the on-time and the duty cycle of the modulation (Ma et al, 2016;Seri et al, 2019). Lower duty cycles result in lower device temperatures, which is preferable for ozone production and minimisation of RNS production.…”