Experimental observation and numerical study on flame structures, blowout limit and radiant efficiency of premixed methane/air in micro-scale planar combustors

•Planar, U-shaped and inclined flames are simulated in micro-planar quartz combustor.•Flame structure is greatly affected by inlet velocity.•Equivalence ratio has little effect on flame type but large impact on blowout limit.•Flame length of inclined flame relative to streamwise direction has a significant effect on blowout limit.•The flame structure and flame location are functions of combustor material.•Combustor with sufficiently large thermal conductivity possesses the broader blowout limit and the higher radiant efficiency. Three-dimensional numerical simulations of methane/air premixed combustion in micro-planar quartz combustor are performed with detailed chemical reaction mechanism. Three types of flame propagation modes including planar, U-shaped and inclined flames are observed with increasing inlet velocity. Numerical results show reasonable agreement with experiments. It is found that flame structure and location are greatly affected by inlet velocity. Meanwhile, the variation of blowout limit with respect to equivalence ratio is non-monotonous, i.e., it increases first and then decreases when the equivalence ratio ranges from 0.9 to 1.1. Further analysis on inclined flame shows that the shorter the flame length, the wider the blowout limit. Moreover, the effect of combustor material on flame structure, flame location and temperature distribution as well as radiant efficiency is studied and compared. Results indicate that thermal conductivity can not only affect the flame structure and flame location, but it can also determine the blowout limit, which is due to the heat recirculation along the streamwise direction. Among the investigated combustor materials, a broadest blowout limit, most uniform temperature distribution and highest radiant efficiency can be achieved in nickel combustor.