Regimes of an atmospheric pressure nanosecond repetitively pulsed discharge for methane partial oxidation

Abstract

Abstract The operation of a nanosecond repetitively pulsed discharge for partial oxidation of CH 4 is characterized at atmospheric pressure and room temperature. Two regimes are observed: diffuse and filamentary. The first is a low power regime, characterized by low rotational temperatures around 400 K. The second is much more energetic with rotational temperatures close to 600 K. Both have vibrational temperatures of at least 10 times their rotational temperatures. The average electron number density was determined to be <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mstyle displaystyle="false"> <mml:mn>8.9</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mn>15</mml:mn> </mml:mrow> </mml:msup> </mml:mstyle> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mstyle displaystyle="false"> <mml:mn>4.0</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mn>17</mml:mn> </mml:mrow> </mml:msup> </mml:mstyle> </mml:math> cm −3 , respectively, showing an increase in the ionization fraction in the more powerful filamentary regime. Results of CH 4 conversion to H 2 , CO, CO 2 and C 2 H 6 are presented for the filamentary regime, while the diffuse regime shows no measurable conversion ability. As expected, oxidative mixtures show higher conversion ability than pure CH 4 . A maximum conversion efficiency of 26.3% and a maximum energy efficiency of 19.7% were reached for the oxidative mixtures.