Study on repetitive extinction-ignition characteristics of methane/oxygen combustion in micro tube combustor

The FREI dynamics of methane/oxygen mixture were observed experimentally in a micro quartz tube combustor. A 2-D model was used to predict propagation features of FREI flame and the simulation results are in good agreement with the experimental results. According to the flame velocity and the wall heat flux obtained from simulation data, four stages of flame front propagation were revealed, namely accelerating stage, decelerating stage, reverse propagating stage and weak reaction stage. Further investigation on flame front propagation were taken in the view of radical analysis and heat release rate (HRR) analysis. Main elementary reactions that contributed to the HRR were acquired. Results revealed that the regeneration of CH4 behind the flame front and the reducing consumption of the overall quantity of methane caused the deacceleration of the flame. The extinction of the flame was due to the negative HRR in the combustor. After the extinction of the flame, the consumption of methane tended to exist along the combustor wall owing to the high wall temperature.