Behavior of methane flame in the channel type meso-combustors

Due to the abundant nature of hydrocarbon fuels, combustion of methane is very promising in the field of micro-combustion. In the current research, the channel type meso-combustors made of copper have been chosen to investigate the flame dynamics and the stability of a methane flame in different operating and geometric conditions. The combustors that have been investigated are as follows: a 20-mm 3-inlet, a 40-mm 3-inlet, and a 40-mm 5-inlet. Hydrogen-assisted methane flames and methane flames with pure oxygen are presented in the current research. It has been found that the methane flame cannot sustain with air as an oxidizer in the meso-combustor for a non-premixed mixture. The combustion of hydrogen-assisted methane combustion can be achieved for a very narrow range of mass flow rates and a very narrow range of overall equivalence ratios. For a hydrogen-assisted flame the stability of the 20-mm combustor is the lowest among all the combustors. The premixed methane-air-hydrogen with air as the oxidizer was found to be more stable than the other combustors. The 40-mm 3-inlet combustor was found to have improved stability compared to the 20-mm 3-inlet combustor. The ratio of hydrogen to methane is the key factor that controls the stability in this case of hydrogen-assisted methane combustion. The higher the ratio is, the higher the stability is for a given mass flow rate. The flame stability increases significantly when instead of air, O₂ is used as the oxidizer and the flame is highly stable for both 40-mm 5-inlet and 40 mm 3-inlet combustors for a wide range of equivalence ratios. The flames have been found to survive for both extreme lean and rich mixtures for a given mass flow rate for CH₄-O₂ combustion.