A numerical study of the stabilization mechanism of an autoignited laminar methane/hydrogen lifted jet flame in heated coflow

Abstract

A temporal evolution of methane/hydrogen mixtures in the laminar heated coflow jet is numerically simulated using laminarSMOKE with 30-species skeletal methane/air kinetic mechanism. The result shows that an ignition kernel first develops at the far downstream of the final stabilization location, and it propagates upstream until the overall flame structure exhibits the stationary lifted flame. From the calculation of displacement speed of flamebase at each different time, it is verified that an autoignition is dominant during the early stage of flame development right after the ignition kernel generation, and the flame propagation becomes dominant when the lifted flame is stabilized by balancing with the local flow velocity. In addition, the 1-D laminar flame speed calculation with various upstream temperature conditions supports that flame propagation is a key stabilization mechanism in lifted flame by showing that density weighted displacement speed of flamebase at steady state is within the range of the calculated 1-D laminar flame speed.