Kinetic Effects of Non-Equilibrium Plasma on Partially Premixed Flame Extinction

The kinetic effects of plasma assisted fuel oxidization on the extinction of partially premixed methane flames was studied at 60 Torr by blending 2% CH4 into the oxidizer stream. The experiments showed that the non-equilibrium plasma can dramatically accelerate the fuel oxidization at low temperature. The prompt fuel oxidization resulted in fast chemical heat release and extended the extinction limits significantly. The O production and the products of plasma assisted fuel oxidation were measured, respectively, by using twophoton absorption laser-induced fluorescence (TALIF) method, Fourier Transform Infrared (FTIR) spectrometer, and Gas Chromatography (GC). The product concentrations were used to validate the plasma assisted combustion kinetic model. The comparisons showed the kinetic model over-predicted the CO, H2O and H2 concentrations and under-predicted CO2 concentration. The O concentration prediction from the kinetic model intersected with experimental results. A path flux analysis showed that O was majorly generated by the discharge and dictated the plasma assisted fuel oxidization. So the deviation between experiments and simulations was caused by the inaccurate prediction of O. This is due to missing reaction pathways, such as those involving excited species (e.g. excited O) and the validity of radical consumption reactions with hydrocarbon species at low temperature range.