Spectroscopic Diagnostics of Rotating Gliding Arc Plasma Codriven by a Magnetic Field and Tangential Flow

Abstract

Rotating gliding arc (RGA) discharge, codriven by a magnetic field and tangential flow, has recently received increasing attention as an innovative technique for generating nonthermal equilibrium plasma at atmospheric pressure. To understand further the mechanism of RGA plasma applied in antipollution and the syngas production industry, optical emission spectroscopy, as a diagnostic technique, was applied to characterize the major active species (radicals, ions, atoms, and excited molecules) and energetic electrons in an RGA plasma. Nitrogen, air, and argon were selected as carrier gases. The electron excitation temperature of the argon plasma was derived from a Boltzmann plot by analyzing the atomic spectral lines of argon and determined to be approximately 1.5 eV as a function of operating conditions. The active species generated in the air and nitrogen discharges were identified. The results indicated that the bands of the second positive system of N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and the bands of the first negative system of N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> were dominant in the nitrogen discharge, whereas additional bands of the NO γ system and OH(A-X) appeared in the air discharge. The variation trends of the emission intensities of the selected spectral bands, such as those of NO(259.5 nm), N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> (391.4 nm), N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (337 nm), and OH(309 nm), were investigated by varying the applied voltage and gas flow rate. The effects of these variations on the abovementioned active species were investigated in terms of the relative intensity of spectral emission to deduce the kinetic mechanism governing the observed reactions.