Kinetics in gas mixtures for problem of plasma assisted ignition

Experiments and numerical modelling of ignition of hydrocarbon-containing mixtures under the action of pulsed nanosecond discharge have been performed. The experiments were carried out using a shock tube technique in a set of stoichiometric mixtures C_nH_2n+2: O₂ (10%) diluted by Ar (90%) for hydrocarbons from CH₄ to C₅H ₁₂. The temperature behind the reflected shock wave (T₅) varied from 650 to 2000 K, and the pressure (P₅) was 0.2 to 1.0 atm. For each set of experimental parameters, the ignition by the discharge was compared with autoignition. Numerical simulation was divided into two steps. First, we calculated production of active species of a stage of the discharge and its nearest afterglow. At this stage, experimentally obtained dependencies of electric field and energy input vs time were used to calculate gas excitation by the discharge. In early afterglow immediately after discharge electronically excited species, like Ar, were quenched giving an additional production of atoms and radicals. Second, the obtained density of atoms and radicals was taken as an initial parameter for calculations of chemical kinetics in a microsecond time scale. As a result, the shift of the ignition delay time for all investigated mixtures has been obtained and compared with the experimental data.