A numerical study on CH4 and air premixed combustion inside a small tube with a temperature gradient was undertaken to investigate the effects of inlet velocity, equivalence ratio and combustor size. The simulation results show that the inlet velocity has a significant influence on the reaction zone, and the flame front shifts downstream as the inlet velocity increases. The results also show that, the inlet velocity has no obvious effects on the flame temperature. The highest flame temperature is obtained if the equivalence ratio is set to 1. It is disclosed that the combustor size has a very strong effect on combustion characteristics. The smaller the combustor size is, the more difficult it is to maintain the steady combustion. The smallest combustor size that the stable flame can be sustained is determined mainly by the wall temperature of the microcombustor under the given conditions, and the higher the wall temperature is, the smaller the smallest combustor size. Therefore raising wall temperature is an effective way to realize flame stabilization for a given combustor size.

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