Impact of Plasma Actuation on the Stability of a Co-Flow Premixed Methane-Air Flame under Lean Conditions

The present work shows a preliminary investigation of the impact of plasma actuation on lifted flame stabilization in a methane CH4-air Bunsen burner at ambient conditions. A high voltage (HV)/high frequency sinusoidal signal has been considered for the investigation. Also, different plasma actuator configurations have been tested, which differently ionized the flame detachment region immediately outside the Bunsen outlet and affected the flame behavior and reattachment. Experimental investigations were complemented by a numerical study, which allowed explaining the effect of each actuator configuration on the flow. Therefore, once the best actuator configuration was selected, the efficiency of the plasma actuation has been evaluated in terms of flame anchoring capability and actuator dissipated power (while keeping the fuel-to-air equivalence ratio Phi fixed around 0.035). In particular, iorder to change the actuator power dissipation, different peak-to-peak voltages V-pp were tested, while the actuation frequency was kept equal to 20 kHz. Results showed that the plasma actuation allowed reattaching the flame with a negligible dissipated power (about 0.05 W). Other equivalence ratios were then tested by increasing the air flow rate and keeping constant the fuel flow rate. Results showed that we can operate at very lean conditions (Phi around 0.021) with a power dissipation lower than 0.1 W.