The effect of fuel oxidation on electron swarm properties and nanosecond discharge characteristics in combustible mixtures
The results of the calculations of electron transport and rate coefficients in oxidized methane:O2, propane:O2 and H2:O2 mixtures were presented for different temperatures and reduced electric fields E/N from 1 to 3 × 103 Td. The calculations were made for various oxidized fuel fractions. It was shown that fuel oxidation led to a drastic decrease in the average electron energy, electron drift velocity and attachment coefficient for E/N < 60 Td. At higher reduced electric fields, the effect of fuel oxidation on the average electron energy and electron drift velocity was small, whereas the attachment coefficient increased with increasing oxidation degree. In addition, in the hydrocarbon-containing mixtures for E/N ∼ 30 Td, the electron drift velocity varied nonmonotonously with the oxidation degree increase. The critical reduced electric field at which the average rate of electron production in the mixture was equal to the average attachment rate increased with fuel oxidation due to the increased attachment rate and decreased detachment rate. The effect of intermediate species on the electron transport and rate properties in partially oxidized mixtures was small. The calculated results were used to self-consistently simulate fuel oxidation and plasma characteristics for high-voltage nanosecond repetitive discharges in combustible mixtures. Zero-dimensional simulation in a H2:O2 mixture showed that the reduced electric field at the instant when the deposited energy peaked was close to the critical values of E/N and increased with increasing oxidized fuel fraction.