Abstract
Translational, rotational, vibrational and electron temperatures of a gliding arc discharge in atmospheric pressure air were experimentally investigated using in situ, non-intrusive optical diagnostic techniques. The gliding arc discharge was driven by a 35 kHz alternating current (AC) power source and operated in a glow-type regime. The two-dimensional distribution of the translational temperature (Tt) of the gliding arc discharge was determined using planar laser-induced Rayleigh scattering. The rotational and vibrational temperatures were obtained by simulating the experimental spectra. The OH A-X (0, 0) band was used to simulate the rotational temperature (Tr) of the gliding arc discharge whereas the NO A-X (1, 0) and (0, 1) bands were used to determine its vibrational temperature (Tv). The instantaneous reduced electric field strength E/N was obtained by simultaneously measuring the instantaneous length of the plasma column, the discharge voltage and the translational temperature, from which the electron temperature (Te) of the gliding arc discharge was estimated. The uncertainties of the translational, rotational, vibrational and electron temperatures were analyzed. The relations of these four different temperatures (Te>Tv>Tr >Tt) suggest a high-degree non-equilibrium state of the gliding arc discharge.
Highlights
Gliding arc discharges provide a simple and low-cost method for generating atmospheric pressure plasma discharges [1,2,3,4]
It should be emphasized that the laser sheet with a twodimensional structure is fixed at the focal plane of the ICCD camera whereas the plasma column of the gliding arc discharge with a transient three-dimensional character moves into the field of view of the ICCD camera
The uncertainty of the electron temperature primarily comes from the indirect determination by use of the reduced electric field strength that is affected by the translational temperature and the length of the plasma column
Summary
Gliding arc discharges provide a simple and low-cost method for generating atmospheric pressure plasma discharges [1,2,3,4]. During the past decades gliding arc discharges have been widely used in combustion enhancement [5,6,7], gas conversion and decomposition [8,9,10,11], bacterial inactivation [12, 13], surface treatment [14, 15] and pollution control [16,17,18] Many of these applications rely on the formation of reactive species that can increase chemical reaction rates [19, 20]. Reactive species, such as free radicals, excited species and free electrons, can be effectively produced in non-thermal plasmas [21], which are characterized by different translational, rotational, vibrational and electron temperatures. Fridman et al [6,28] calculated the rotational (~2200-2500 K) and vibrational (~3200-3700 K) temperatures of a magnetically stabilized gliding arc discharge by simulating the experimental OH (A–X) and N2 (C–B) bands using the SPECAIR program [29]
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