About the Development and Dynamics of Microdischarges in Toluene-Containing Air

Abstract

The development of microdischarges and the inception dynamics of subsequent microdischarges in an electrode arrangement consisting of a metal pin and a hemispherical dielectric-covered electrode, operated in air with a small toluene admixture, is studied. The discharge is operated with sinusoidal high voltage. A gated ICCD camera and a current probe enable the recording of images and current pulses of the single microdischarges, respectively, while the spatio-temporally resolved development is measured with a multidimensional time-correlated single photon counting technique. The overall discharge dynamics changes significantly if a concentration of 35 ppm toluene is added to dry air. A lower high voltage amplitude than in dry air is needed for stable discharge operation. This can be explained by the lower ionization energy of toluene compared to molecular oxygen and nitrogen. The microdischarge development is the same with or without admixture, i.e. a positive (cathode directed) streamer mechanism is observed. Lower mean power is dissipated into the discharge when toluene is admixed. The main effect caused by toluene admixture is the suppression of high-energy microdischarges in case of the cathodic pin half-cycle of the sinusoidal high voltage. The influence on the inception voltage by additional ionization mechanisms and volume memory effects, the consumption of energetic electrons for toluene decomposition reactions, and the modification of the surface by plasma treatment are discussed as possible reasons.

Experimental investigation of single microdischarges in a barrier corona arrangement with a cathodic metal pin

“…In other words, MDs appearing before 7 μs in the cathodic pin half-cycle usually follow an anodic pin halfcycle, in which the second MDs were ignited later and featured a higher current pulse amplitude. A similar correlation was also found when the appearance of second group MDs was influenced by a small toluene admixture [21]. In the following anodic pin half-cycle, the appearance of the first group MDs is concentrated at the earlier phases, and the CPAH is shifted to slightly higher current values.…”

“…The results of the anodic pin half-cycle were presented in a previous contribution [20]. In addition, general appearance and characteristics of the discharge with 35 ppm toluene admixture in air were presented in [21]. In the current contribution, the results of the cathodic pin half-cycle are presented and discussed in detail.…”

Papers by Selected Lecturers at the 11th International Symposium on Non-thermal/Thermal Plasma Pollution Control Technology & Sustainable Energy (ISNTPT 11)

“…While the emission of nitrogen oxides continues to be a significant air pollution issue [12], the community of plasma researchers has broadened its approach to the study of nitrogen oxides to include synthesizing such species in gas-liquid plasma with air/nitrogen/oxygen mixtures for biomedical and agricultural applications (Hoeben et al [13], Pawlat et al [14], and Wandell et al [15]). Volatile organic compounds removal by gas phase plasma using dielectric barrier discharges is also of significant and continuing interest and here Brandenburg et al [16] reports on the analysis of microdischarge formation in this system. Plasma combustion and plasma enhanced combustion (Filimonova et al [17]), as well as H 2 formation from biosyngas (Hrycak et al [18]) are important new topics not covered in the first meeting.…”