Increased arc length and stability in a magnetic gliding arc discharge using a cylindrical notched cathode

Abstract

Intermediate arc discharge plasmas allow for working with ions at lower temperatures than thermal plasmas and can generate greater selectivity in certain chemical reactions due to the high vibrational and electron temperature. In this paper, a magnetic gliding arc discharge (MGA), which is an intermediate plasma, was developed and is described. The reactor is operated with CO2 as the working gas, but open to atmosphere. It presents increased arc length and stability by using a cylindrical notched cathode (CNC). The constructed rectangular section of the notch channel on the cylindrical cathode surface allowed the arc to be confined within the channel with enhanced stability. The changes in the cathode geometry allowed the system to reach radial arc length of 40 mm, plasma disc diameter of 102 mm, and from 300 to 400 mA of current. A low cost electro-optical device was set up to determine the arc rotation frequency and is described in detail. Measurements of frequency (f) as a function of current (I) indicates that the developed MGA-CNC follows the relation f∝ I0.5, which agrees with the theoretical prediction. In order to compare the MGA-CNC data acquired with other reported MGAs, an analysis considering the distinct magnetic field intensities (Br) and different cathode diameters (D) was performed. Thus, a linear relationship was observed for f D/(Br=D/2)1/2 as a function of I1/2, which may represent the general experimental behavior of different MGA operated in air at atmospheric pressure. The arc diameter (d) in the region near the cathode (at r = D/2) can be determined from the slope α of the plot (α = 6.03 m kg−1/2); the obtained value (d = 3.2 ± 0.7 mm) is coherent with measured values elsewhere.