Multi-hollow Surface Dielectric Barrier Discharge: Production of Gaseous Species Under Various Air Flow Rates and Relative Humidities

Abstract

An evaluation of the gaseous species production by the discharge, i.e., discharge chemical activity, is very important for determining its potential for practical applications. In this work, production of gaseous species by the multi-hollow surface dielectric barrier discharge generated in a perforated ceramic substrate with the air-exposed electrode is investigated under conditions of various discharge powers (1–5 W), air flow rates (0.25–2.4 L/min) and air relative humidities (0–80%). Production of ozone O3, nitrous oxide N2O, nitric oxide NO, nitrogen dioxide NO2, dinitrogen pentoxide N2O5 and nitric acid HNO3 is evaluated in terms of concentration (ppm), production yield (g/kWh) and production rate (mg/h). The work demonstrates a critical impact of both air flow rate and relative humidity on prevailing discharge mode (“O3 mode” vs. “NOx mode”) and, thus, on overall composition and concentration of produced gaseous species. For low discharge power, the discharge operates in the “O3 mode”, when O3, N2O, N2O5 and HNO3 are dominant gaseous products. With the increasing power, the discharge transfers into the “NOx mode”, when N2O and HNO3 along with NO and NO2 are mostly produced. In dry air, transition from “O3 mode” to “NOx mode” is found for the specific input energy of 1000–1100 J/L. With an increase of air relative humidity from 20 to 80%, the transition gradually decreases from approximately 600 to 450 J/L, respectively.