Numerical study of the effect of wall temperature profiles on the premixed methane–air flame dynamics in a narrow channel

Abstract

Time-accurate simulations of premixed CH₄/air flame in a narrow, heated channel are performed using the DRM-19 reaction mechanism. The effect of different wall temperature profiles on the flame dynamics is investigated for three different inflow velocity conditions. At a low inflow velocity of 0.2 m s⁻¹, the flame shows instabilities in the form of spatial oscillations and even flame extinction. With the increase of the inflow velocity, flames are prone to showing more stability at a medium inflow velocity of 0.4 m s⁻¹, and eventually show flame stabilisation at a high inflow velocity condition of 0.8 m s⁻¹ for all the wall temperature profiles examined. The total chemical heat release rate and total gas–solid heat exchange rate are found to have a combined effect on the flame propagation speed that determines flame behaviours. Since the flame behaviours in terms of the oscillation frequency and amplitude for spatially oscillating flames, or the stream-wise stabilisation location for steady-state flames, are very sensitive to the chosen wall temperature profile, a “real” conjugate heat transfer model is recommended in order to capture all of the relevant combustion physics accurately.