Kinetic development of low-temperature propane oxidation in a repetitively-pulsed nanosecond discharge

The kinetics of plasma assisted low temperature oxidation of $C_3{H}_8/O_2/Ar$ mixtures have been studied in a wide specific deposited energy with the help of nanosecond repetitively pulsed discharge. Two types of nanosecond pulsed plasma sources, the nanosecond capillary discharge (nCD) and dielectric barrier discharge (DBD) combined with the synchrotron photoionization mass spectrometry are investigated. The electron impact reaction rate of propane dissociation and some combustion chemical reactions rate constants are updated according to the nCD and DBD experiment results, and uncertainty of the reactions are analyzed in detail. Compared to the existing model, the updated model’s prediction accuracy has great improvement in species $H_{2}O$, $C{O}_2$, $C{H}_4$, $C{H}_{2}O$, $C{H}_{3}OH$, $C_2{H}_2$, $C_2{H}_6$, $C_2{H}_{5}OH$, $C_2{H}_{5}OOH$, $C_3{H}_4$-$A$, $C_3{H}_4$-$P$, $C_2{H}_{5}CHO$, $i$-$C_3{H}_{7}OH$ and $C_3{H}_{7}OOH$. The propane oxidation processes assisted by DBD and nCD were compared under different single pulse deposited energy (SPDE) conditions while maintaining the same total deposited energy. The reduced electric field in nCD is concentrated at 150-200 Td and 450-500 Td, whereas in DBD it ranges from 1-100 Td and 260-380 Td. Notably, for nCD at different voltages with a similar reduced electric field distribution, SPDE shows minimal influence on the $C_3{H}_8$ oxidation process, which is primarily governed by total deposited energy. nCD is more effective discharge form for contribute to $C_3{H}_8$ dissociation compared to DBD.

Novelty and significance statement

The study of plasma assisted fuel conversion and efficient combustion requires precise data on plasma chemistry and combustion chemical reaction kinetics. However, the computational complexity of excited state reaction kinetics data based on first principles is enormous, resulting in a scarcity of relevant basic data. Propane, as a relatively large molecule, is an important object for studying its low-temperature oxidation pathway in plasma ignition and combustion assistance. The research that was lacking in the early stage mainly used analogy estimation and limited experimental research on a few reactions. In this work we revised the reaction kinetics mechanism of propane low-temperature oxidation reaction by constructing two independent experiments, and discussed the general effects of energy deposition and electric field (which are the key parameters of a plasma system) on propane plasma low-temperature oxidation. This study can serve as a foundation and reference for studying plasma pyrolysis of macromolecular fuels.