Near-wall dynamics of premixed methane/air flames

This work focuses on sidewall quenching (SWQ) for premixed methane/air flames that are forced by a periodic oscillatory inflow with excitation frequency f = 100 Hz. The effects of steady-state and transient flame stretch on the near-wall flame dynamics are evaluated using two-dimensional direct numerical simulation (2D-DNS) and the GRI 3.0 reaction mechanism. The velocity fluctuations lead to significant changes in flame speed and flame stretch, as well as the associated Markstein numbers. The phenomenon of SWQ is analyzed using flame quenching distance, wall heat flux and heat release rate. For steady-state conditions, there is a strong correlation between the maximum wall heat flux (WHFmax) and the flame quenching Peclet Number (Peq), as well as between the flame speed and the flame stretch; for transient conditions, the flame quenching distance (dq) increases continuously from phase angles of 1/4f-1 to 3/4f-1 in one cycle as time progresses, and the fluctuation of the quenching distance (Delta dq) decreases gradually with increasing equivalence ratio ( null ). The flame stretch changes from negative to positive in the process from 1/4f-1 to 3/4f-1, while the heat release rate and fuel reaction rate near the wall gradually decrease. Furthermore, the FWI region is dominated by negative flame stretch while positive flame stretch is present at the base of the flame. Moreover, the methane/air flame has a nearly twofold increase in the consumption speed during the oscillation from phase angle 3/4f-1 to the next cycle at 1/4f-1 at null = 0.5 and null = 1.0. These results show that flow field perturbations are not negligible in elucidating the effects of flame-wall interactions.