Plasma-chemical kinetic study for low-temperature oxidation of hydrogen

Plasma assisted combustion has been extensively investigated for the last couple of decades. Non-thermal plasmas, in particular, have been found to improve ignition characteristics and promote detonation. However, due to a lack of fundamental understanding of the plasma-chemistry involving hydrocarbons, modeling of the plasma kinetics as predictive tool development is running behind as compared to physical modeling of the plasma. Here, we present a kinetic study for H₂/O₂/(Ar) mixtures to establish a foundation for plasma-assisted hydrocarbon combustion systems. We used a temperature-controlled dielectric barrier discharge (DBD) reactor and a gas chromatography to obtain experimental data; we developed a chemical kinetic platform to simultaneously calculate electron-induced chemistry (ZDPlaskin) and thermally induced chemistry (ChemKin). Through systematically varying the reaction temperature, the equivalence ratio of the mixture, and the discharge power, we discovered somewhat negative temperature behavior for the H₂ conversion in a temperature range of 600–750 K. However, this behavior was found to be influenced not only by the gas temperature but also by the reduced field intensity, indicating the importance of electron-induced chemistry. Additionally, we found the inevitable and undesirable chemical effect of a balance gas (Ar, He, N₂) on the plasma-chemical kinetics, showing significant role of excited (metastable) states on the dissociation of H₂ and O₂ in a highly diluted system. This clearly shows that future kinetic studies for plasma assisted combustion should be conducted using a practical balance gas.

 

Acknowledgements: The research reported in this presentation was funded by King Abdullah University of Science and Technology (KAUST), under award number BAS/1/1384-01-01.