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A new method for the interneedle-distance optimization of a multineedle-to-plane barrier discharge reactor is presented. As we know, there is gas breakdown when, in some regions between electrodes, the electric field is higher than the breakdown field; hence, the regionmay play a dominant role for the discharge, and the enhancement of its volume ratio in the reactor will allow an increase in discharge energy density. This can be achieved by structure optimization. With the finite-element method, the 3-D profiles of an electrostatic field in the reactor are acquired for a series of interneedle distances, thereby the one-to-one relationship between the volume ratio and interneedle distance is obtained. This allows the optimal interneedle distance for power input efficiency to be identified, as related to the maximal volume ratio. The optimal distance is between 7.2 and 8.4 mm in our simulation range, decreasing with the increase of operating voltages from 16 to 26 kV. The simulation results are experimentally validated by discharge energy measurement as well as the performance of SO2 removal from indoor air. This structure optimization method leads to a simple way to obtain the optimal interneedle distance for energy input efficiency and hence benefits commercial use. [ABSTRACT FROM AUTHOR]

Dielectric barrier discharge is attractive for air pollution control, except for its low energy efficiency and high operating voltage. For the sake of commercial use, multineedle to plane electrodes is investigated in this paper, and its optimization is achieved both by simulation and experiments. [ABSTRACT FROM AUTHOR]

The dielectric breakdown properties of hot SF6 gas during the dielectric recovery phase play an important role in understanding gas breakdown occurring in high-voltage circuit breakers. This paper is devoted to the theoretical investigation of dielectric breakdown properties of hot SF6 gas contaminated by copper at temperatures of 300–3500 K and pressures of 0.01–1.6 MPa. The equilibrium compositions of SF6–Cu mixtures are obtained with the consideration of condensed species. The unknown ionization cross sections for CuS, CuF and CuF2 are calculated using a Deutsch–Märk (DM) formalism based on quantum chemistry. The two-term Boltzmann equation is adopted to numerically calculate the electron energy distribution function, collision ionization coefficient and electron attachment coefficient. Then the reduced critical electric field strength is determined when the effective ionization coefficient equals to zero. The influences of the Cu proportion and gas pressure on the dielectric breakdown properties are investigated. It is shown that the existence of copper compounds increases the concentration of high-energy electrons significantly, even for the case with a very low percentage (e.g. 1% Cu). With the increase of copper content, the value of (E/N)cr is reduced remarkably at temperatures below 3000 K, but enhanced slightly above 3000 K. It is also found that the increase of pressure can improve the dielectric breakdown performance of hot SF6–Cu mixtures. [ABSTRACT FROM AUTHOR]