Effect of solid material on the blow-off limit of CH4/air flames in a micro combustor with a plate flame holder and preheating channels

It is challenging to achieve a wide operational range in micro combustors due to the increased heat loss. In the present work, a micro combustor with a plate flame holder and preheating channels is developed. Three kinds of solid materials (i.e., stainless steel, SiC and copper) are chosen to investigate the heat recirculation effect on the flame blow-off limit of this micro combustor. The results show that, even for very lean CH4/air mixtures, this micro combustor can achieve a very large flame blow-off limit, which confirms its excellent flame stabilization ability. Moreover, the copper combustor has a widest operational range while the SiC combustor has the poorest performance. The analysis reveals that a large blow-off limit is mainly attributed to a good heat recirculation effect, which relies upon both the thermal conductivity and the surface emissivity of the solid material. It is also demonstrated that the differences in the recirculation-zone lengths are small, which is not expected to be a dominant factor that responsible for the differences in the blow-off limits of the three combustors. In conclusion, to obtain a large flame blow-off limit, a solid material with a large thermal conductivity and a small emissivity is suggested to fabricate this kind of micro combustor.