A numerical study on the methane flame in a rapidly mixed tubular flame burner

The rapidly mixed tubular flame generally provides a well controlled premixed laminar flame without hazards of flame flash back even for reactants with high burning velocity. In this study, the open-source software OpenFOAM was used to simulate the methane combustion diluted by N2/CO2 in a rapidly mixed tubular flame burner by the Large Eddy Simulation. The main objective is to obtain fundamental characteristics of the flame structure, velocity, temperature, and products. The flow fields of methane/air mixture under cold flow and combustion conditions were discussed. The results show that under cold flow condition, the radial and tangential velocity increased almost linearly with radial distance, reached their peaks, and gradually decreased. For the combustion, the velocities distributions varied significantly with those of cold flow inside the flame front, whereas their distributions were almost same outside the flame front. The intense reverse flow observed in the cold flow became weak in the flame owning to so called vortex bursting. The temperature was almost evenly distributed along the radial direction, and the wall temperature near the tangential inlet was relatively low. The oxy-methane flame with oxygen concentration of 0.5 shows almost the same flow field, however yields less CO and NO emissions.