Characteristics of methane combustion in a micro combustor with heat insulation

The characteristics of a micro Swiss-roll combustor were studied by burning premixed CH₄/air in the combustor to obtain combustion limits at various methane flow rates and to analyze combustion products. The results show that premixed CH₄/air can stably combust in the combustor with the flame kept in the center of the combustor. Flammability limits are only extended if the heat transfer between the combustion products and the unburned gas exceeds upper and lower unsymmetrical limits of the stoichiometric equivalence ratio (ER) of air to CH₄. The large fuel-lean limit sustains stable combustion in the combustor at large air flow rates. The highest wall temperature occurs in the combustor center where the ER is a little larger than 1, with the flame temperature gradually decreasing with increasing air flow rate. If the ER is larger than 1, the CH₄ is completely oxidized, but if the ER is less than 1, excess CH₄ is converted to CO and H₂ which produces less combustion heat; thus, destabilizing the combustion.