Dynamics of premixed CH4/air flames in a micro combustor with a plate flame holder and preheating channels

It is challenging to achieve a wide flammable range in micro combustors due to the increased heat loss. In the present work, the flammable range based on equivalence ratio for a novel micro combustor is investigated, and some interesting dynamic flame behaviors are observed, which include the flame blow-off, pulsating flame and the flame with repetitive flashback and pulsating (FRFP). Our analysis indicates that the above flame behaviors mainly depend on the competition of the burning velocity and flow speed. For the lean fuel, a higher equivalence ratio leads to a faster burning velocity and a higher preheating temperature. A higher preheating temperature further elevates the burning velocity as well as the flow speed of incoming gas mixture. The faster burning velocity makes the flame shift upstream, but the bigger flow speed pushes the flame downstream. In such a way, the increase of equivalence ratio gives rise to the increase of burning velocity and flow speed, and the burning velocity increases faster than the flow speed. In addition, the flame dynamics distributions are almost symmetrical with respect to the stoichiometric ratio, i.e., the flame behaviors under lean and rich fuel are the same basically.