Regime Transitions of a Pulsed Nanosecond Discharge Driven by Dynamic Flame Instabilities

Pulsed Nanosecond Discharges are being investigated for suppressing dynamic flame instabilities of lean flames. In this dynamic environment, the gas condition is changing significantly in both composition and temperature at the timescales of the pressure oscillations. This changes the ionization characteristics of the gas, due to different ionization thresholds/cross sections as the reaction progresses, as well as by changes to the reduced electric field as the temperature rises. This contribution will report on the experimental characterization of a discharge used for stabilization of dynamic flame instabilities in a 14kW swirl-stabilized combustor. The discharge properties, in terms of its regime and energy deposition, are a strong function of where the flame is in its instability cycle. Understanding the causes of this transition and the two-way coupling between the plasma and the gas is critical for designing the plasma actuation and control scheme. The presentation will focus on experimental demonstration of the flame's effect on the plasma and discussion of the methods of interaction and the implications for designing the plasma actuation strategy.