Methane-air partially premixed flame behaviors in a micro plate slit

The size of the combustion space has a significant effect on the flame behavior in the micro combustor. In this paper, the structures and dynamics of laminar partially premixed methane/air were experimentally investigated as the combustion space gradually decreases. In the experiment, five flame regimes were observed in sequence: the stable flame, transient oscillating flame, extinction, flame with repetitive extinction and ignition (FREI), and quenching. The effects of the mixture flow rate, primary equivalence ratio, and separating distance of plates on the different flame behaviors were analyzed. It was revealed that increasing the mixture flow rate could improve the flame's stability while increasing the primary premixed air, and the flame tended to become unstable. Moreover, in the FREI regime, the larger the separating distance, the lower the frequency of the FREI flame; meanwhile, the FREI frequency increased as the primary equivalent ratio decreased. The FREI frequency exhibited a non-monotonic change with the mixture flow rate and peaked at 1.06 m/s. Furthermore, it was demonstrated that the smaller the primary equivalent ratio, the smaller the quenching distance. The mixture flow rate had no significant effect on the quenching distance. The research is helpful to the design of the micro combustion device.