Kinetic mechanism of plasma recombination in methane, ethane and propane after high-voltage nanosecond discharge

Abstract

The results of the experimental and numerical study of high-voltage nanosecond discharge afterglow in pure methane, ethane and propane are presented for room temperature and pressures from 2 to 20 Torr. Time-resolved electron density during the plasma decay was measured with a microwave interferometer for initial electron densities in the range between 5 × 10 10 and 3 × 10 12 cm −3 and the effective recombination coefficients were obtained. Measured effective recombination coefficients increased with gas pressure and were much higher than the recombination coefficients for simple molecular hydrocarbon ions. The properties of plasma in the discharge afterglow were numerically simulated by solving the balance equations for charged particles and electron temperature. Calculations showed that electrons had time to thermalize prior to the recombination. The measured data were interpreted under the assumption that cluster hydrocarbon ions are formed during the plasma decay that is controlled by the dissociative electron recombination with these ions at electron room temperature. Based on the analysis of the experimental data, the rates of three-body formation of cluster ions and recombination coefficients for these ions were estimated.

The Effects of Pulse Shape on the Selectivity and Production Rate in Non-oxidative Coupling of Methane by a Micro-DBD Reactor

“…Also, due to a high reduced electric field, they can generate high densities of charged particles at low values of specific deposited energy, which leads to higher energy efficiencies. All the above-mentioned features can be controlled by a wide range of adjustable parameters of pulsed power supply such as pulse repetition frequency, pulse shape, pulse rise time, pulse fall time, pulse width, and pulse voltage amplitude [16,21,[32][33][34].…”

The effect of electron heating on plasma decay in H2:O2 mixture excited by a repetitively pulsed nanosecond discharge

“…The electron density was determined from the phase shift between these waves [28]. The experimental error of the electron density measurements was around 30% [29].…”

Kinetics of charged species in non-equilibrium plasma in water vapor- and hydrocarbon-containing gaseous mixtures

“…Therefore, it is difficult to use the data presented in table 5 for simulating hydrocarbon plasma kinetics. As a zero approximation for considering the kinetics of hydrocarbon cluster ions, the kinetics of plasma decay in some hydrocarbons and hydrocarbon-containing mixtures was experimentally studied and simulated on the basis of simplified assumptions about ion composition [69,70]. It was assumed that the ion composition of hydrocarbon plasmas is dominated by several sorts of simple molecular ions and one sort of cluster ions.…”

“…These values are comparable with the values presented in table 5 for specific hydrocarbon cluster ions. This simplified model allows the simulation of plasma decay after a high-voltage nanosecond discharge under various conditions [69,70] (see also section 4.2).…”

“…Table 9 presents the effective rate coefficients for formation of cluster ions in methane, ethane, propane, ethylene, and dimethyl ether. These coefficients were obtained from electron density measurements during the plasma decay after a highvoltage nanosecond discharge in pure hydrocarbons [69,70] without specifying the ion composition. The measurements were performed in a wide (1-20 Torr) range of gas pressure and allowed estimating the association rate coefficients under the assumption that all hydrocarbon cluster ions are characterized by the same values of association rate coefficients and the same values of dissociative recombination with electrons.…”