Ignition and Development of Flame Kernel Formed by Nano-Second Repetitively Pulsed Discharges (NRPDs) in the Quiescent Lean Premixed Mixture

Abstract

To provide a better understanding of the ignition process using nanosecond repetitively pulsed discharges (NRPDs), ignition trials of quiescent lean propane-air mixtures (equivalence ratio of 0.7) in a constant volume combustion chamber were conducted. Both the post-discharge and the following flame kernel development were visualized and analyzed by high frame rate imaging of the chemiluminescence. NRPD produces a gas motion resulting in a jetting phenomenon and that influence on the time of flame kernel development. For fixed inter-electrode gap and constant total energy, the ignition time was minimized at a certain pulsation frequency, with higher pulse repetition ratio being detrimental and resulting in longer ignition delay times. The effect of energy deposition, pulse repetition frequency (PRF), and inter-electrode gap was attributed to the competition between characteristic recirculation time from the discharge-induced flow field and the inter-pulse time.