Effects of feed gas flow path on ozone generation characteristics using nanosecond pulsed discharge

Low-yield in generation of ozone is a major barrier to expanding utilization of ozone. Ozone generation using nanosecond(ns) pulsed discharge has attracted attention as a high-yield ozonizer; our laboratory has developed a ns pulsed generator producing non-thermal plasma to generate ozone. However, maximum ozone concentration remains lower than that required for industrial application. It is assumed that a main cause of ozone concentration saturation is a gas temperature rise near the H.V. central electrode of the coaxial cylindrical electrodes. Our previous study showed gas temperature rises of 43.5°C at 13.5mm from the central electrode, 36.9°C at 20mm, and 24.3°Cat 30mm; this heat causes ozone molecule decomposition. This paper describes effects of feed gas flow path on ozone generation characteristics using ns pulsed discharge. In this study, experiments were conducted in small scale aiming at practical use of the reactor with varying gas flow paths. The needle-to-plate electrode utilized here is a structure in which feed gas passes through a needle and is then exposed to non-thermal plasma in each of three flow paths: exhale type, inhale type and cross type. Ozone concentrations achieved based on gas flow path and rate were investigated. Results show ozone concentration of the inhale type flow path to be highest due to the high intensity of the ns pulsed electric fields and gas temperature distribution.