Comparative Shock-Tube Study of Autoignition and Plasma-Assisted Ignition of C$_{2}$-Hydrocarbons

The dynamics of pulsed picosecond and nanosecond discharge development in liquid water, ethanol and hexane Using a shock tube with a discharge cell, ignition delay time was measured in a lean ($\varphi \quad =$ 0.5) C$_{2}$H$_{6}$:O$_{2}$:Ar mixture and in lean ($\varphi \quad =$ 0.5) and stoichiometric C$_{2}$H$_{4}$:O$_{2}$:Ar mixtures with a high-voltage nanosecond discharge and without it. The measured results were compared with the measurements made previously with the same setup for C$_{2}$H$_{6}$-, C$_{2}$H$_{5}$OH- and C$_{2}$H$_{2}$-containing mixtures. It was shown that the effect of plasma on ignition is almost the same for C$_{2}$H$_{6}$, C$_{2}$H$_{4}$ and C$_{2}$H$_{5}$OH. The reduction in time is smaller for C$_{2}$H$_{2}$, the fuel that is well ignited even without the discharge. Autoignition delay time was independent of the stoichiometric ratio for C$_{2}$H$_{6}$ and C$_{2}$H$_{4}$, whereas this time in stoichiometric C$_{2}$H$_{2}$- and C$_{2}$H$_{5}$OH-containing mixtures was noticeably shorter than that in the lean mixtures. Ignition after the discharge was not affected by a change in the stoichiometric ratio for C$_{2}$H$_{2}$ and C$_{2}$H$_{4}$, whereas the plasma-assisted ignition delay time for C$_{2}$H$_{6}$ and C$_{2}$H$_{5}$OH decreased as the equivalence ratio changed from 1 to 0.5. Ignition delay time was calculated in C$_{2}$-hydrocarbon-containing mixtures under study by simulating separately discharge and ignition processes. Good agreement was obtained between new measurements and calculated ignition delay times.