Nonequilibrium discharges in air and nitrogen plasmas at atmospheric pressure

Abstract

Diffuse glow discharges were produced in low temperature (<2000 K) atmospheric pressure air and nitrogen plasmas with electron number densities in excess of 1012 cm­3, more than six orders of magnitude higher than in thermally heated air at 2000 K. The measured discharge characteristics compare well with the predictions of a two-temperature kinetic model. Experimental and modeling results show that the steady-state electron number density exhibits an S-shaped dependence on the electron temperature, a behavior resulting from competition between ionization and charge-transfer reactions. Non-Maxwellian effects are shown to be unimportant for the prediction of steady-state electron number densities. The power requirements of DC discharges at atmospheric pressure can be reduced by several orders of magnitude using short repetitive high-voltage pulses. Between consecutive pulses, the plasma is sustained by the finite rate of electron recombination. Repetitive discharges with a 100-kHz, 12-kV, 10-ns pulse generator were demonstrated to produce over 1012 electrons/cm3 with an average power of 12 W/cm3, 250 times smaller than a DC discharge at 1012 cm­3.

Study of a non-equilibrium pulsed nanosecond discharge at atmospheric pressure using coherent anti-Stokes Raman scattering

“…As indicated in Fig. 3, the spectral bands detected by CARS are identified as the Q-branches of the vibrational transitions (0, 1), (1,2) and (2,3). The fine structure is made of the rotational line components of the Raman transitions.…”

“…One alternative method consists on modifying the chemical reaction kinetics by generating and sustaining large electron number densities, which results in a non-equilibrium excitation of the gas mixture. Better efficiency of population transfer within electronic and vibrational states can be obtained using pulsed nanosecond discharges which handle a reduced electric field [1][2][3]. However, the processes of energy transfer between the plasma and the gas medium are not properly known.…”

Numerical studies of nitric oxide formation in nanosecond-pulsed discharge-stabilized flames of premixed methane/air

“…The plasma kinetic mechanism used in this study is systematically reduced from the one proposed by Kossyi et al [18] for dry air and contains electron-impact excitation, dissociation, ionization of N 2 and O 2 , ion conversion, electron-ion recombination, quenching of excited states of N 2 (N * 2 ) by N 2 and O 2 , and other reactions between neutral species [19]. Since the discharge is in a combustible mixture, it will contain CH 4 , CO 2 and H 2 O as major components, and we include electronimpact dissociation, ionization of CH 4 , CO 2 and H 2 O, electron-ion recombination, and quenching of N * 2 by CH 4 and H 2 O. The complete plasma reaction mechanism is presented in table 1.…”

“…Recently, non-equilibrium plasmas have been used for flame holding [3]. Among these non-equilibrium plasma sources, nanosecond-pulsed repetitive discharges have been used because of their effectiveness in creating high-density plasmas with a lower required power budget when compared with other types of plasmas [4]. Studies have shown that these discharges are effective in shortening ignition delay times [5,6] and in flame holding [7][8][9].…”

An atmospheric pressure plasma source driven by a train of monopolar high voltage pulses superimposed to a dc voltage

“…In order to ignite an electrical discharge at atmospheric pressure and maintain the plasma in a regime appropriate to a specific application, various electrical supply schemes, including superposition of a e-mail: stoican@infim.ro a time-varying periodic voltage to a dc voltage, have been described in previous research [6][7][8][9][10]. For the atmospheric pressure plasma source presented in this paper, the high voltages pulses produced by a self oscillating flyback converter (FBC) are superimposed to a relatively low dc voltage.…”