Enhancement of Blowout Limits in Lifted Swirled Flames in Methane-Air Combustor by the Use of Sinusoidally Driven Plasma Discharges

This study focuses on the effects of continuous volumetric discharge of sinusoidal plasma actuator at 20 kHz coupled directly with methane-air premixed flame in the near field of the injector exit. A plasma actuator composed of a needle-type electrode placed at the center of the nozzle, connected with high-voltage, while the nozzle was acted as a grounded electrode with different input electrical power values was designed to enhance lean blowout performance in a swirl model combustor. The ionic wind induced by the electrical body force given by the flow ionization leads to velocity disturbance and subsequently affects the flame. To investigate the possible mechanism of the combustion control by the plasma through the aerodynamic effect high speed flow visualization was analyzed under quiescent conditions. Flow visualizations showed that the plasma discharge affects the flow dynamics near the burner exit. It was observed that by increasing the electrical power used for the actuation a recirculation zone is formed in the non-reacting flow field. Furthermore, comparative experiments between conventional and plasma-assisted combustion were carried out to analyze the combustion enhancement in terms of lean blowout performance. The effect of the input electric power of the plasma actuator was studied, and it was seen that at coupled plasma powers corresponding to less than 1% of the thermal output power, there is a significant improvement in the blow-out limit.