Synergistic effect of the warm plasma discharge and the flow field on the ammonia/air premixed combustion stabilization near the lean blowout limit

This work investigates the synergistic effect of the warm plasma discharge and the flow field on the ammonia combustion stabilization under different discharge powers and swirl numbers by a novel contribution analysis method that integrates the numerical simulation with a theoretical S-curve model. It demonstrates that the warm plasma discharge can change the ignition/extinction limits and thus the morphologies of the S-curves under the assistance of the swirling flow. As the normalized discharge power increases from approximately 5.2 % to 19.6 %, the residence time at the ignition limit decreases exponentially, while that at the extinction limit decreases linearly. As the swirl number increases from 0.25 to 1, the residence times corresponding to the ignition limit and the extinction limit both decrease exponentially, resulting in the S-curve gradually stretching. A theoretically fitting model considering the warm plasma effects and the energy recirculation was further established to predict the ignition/extinction limits and evaluate the respective contributions of the warm plasma discharge and the swirling flow. The results reveal that the ignition limit is mainly governed by the flow field, whose contribution outweighs that of the warm plasma discharge. The extinction limit is jointly governed by the warm plasma discharge and the flow field, with their contributions exhibiting a strong dependence on the swirl number. At low swirl numbers (<0.5), the impact of the flow field on the extinction limit dominates, whereas at higher swirl numbers the warm plasma dominates. The synergistic effect contributes 30 %-40 % to ignition/extinction limits, and its contribution increases with the discharge power and the swirl number for ignition but shows a non‑monotonic dependence on the swirl number for extinction.