Over the last decades, one of the main research fields for application of non-equilibrium plasma discharges has been the enhancement of combustion systems. The idea is to ignite or enhance flames with electrical discharges, by applying an electrical power negligible compared to the thermal power released by the combustion mechanisms. Industrial combustion systems, including IC engines, gas turbines, industrial burners or flares, usually operate at pressures ranging from atmospheric to 40 bar. For this range of pressures, in order to avoid thermal equilibrium of the plasma, different strategies to control the peak current can be used. Among them, nanosecond repetitively pulsed (NRP) discharges have shown promising results to assist combustion. In this study, NRP discharges in the glow regime have been used in order to promote chemical activation of the fluid instead of heating of the gas, as it can been obtained with the spark regime. On a canonical laminar premixed flame, the effect of these micro-discharges on the behavior of the combustion front has been investigated through the formalism of the flame-transfer function (FTF). Measurements of the response of the flame to plasma actuation has been carried out and compared to the response of the flame to acoustic forcing. These results show that the flame is more responsive to plasma actuation than to acoustic actuation. Based on comparisons with 2D simulations of the G-equation, modeling the temporal evolution of the flame front subjected to small perturbations, an explanation for this result is proposed. Results also show that the chemical actuation of the gas by NRP glow discharges could be a good candidate for control of thermoacoustic instabilities in gas turbines and aero engines.

Deanna Lacoste is an assistant professor of mechanical engineering at the King Abdullah University of Science and Technology (KAUST), in Saudi Arabia. She obtained her MS, PhD and Habilitation form the University of Poitiers – ENSMA, in France. She has been post-doctoral fellow and research engineer at the EM2C Laboratory, Ecole Centrale Paris, in France. In 2014, she joined the Clean Combustion Research Center at KAUST. Professor Lacoste’s research focus on plasma-assisted combustion, control of flame dynamics and development of dedicated optical diagnostics. She recently started to work on plasma-assisted detonation.