Autoignition-affected stabilization of laminar nonpremixed DME/air coflow flames

The structure and stabilization mechanism of laminar nonpremixed autoignitive DME/air coflow flames were investigated. Computations were performed at 30 atmospheres with uniform inlet velocities of 3.2 m/s for both streams, and the coflow air boundary temperatures were 700, 800, 900, and 1100 K. The heat release rate and species profiles were examined for each case. Further investigation with Chemical Explosive Mode Analysis (CEMA) and Lagrangian Flamelet Analysis (LFA) were performed to identify the controlling chemistry and elucidate the dominant combustion mode and stabilization mechanism. At 700-900 K, autoignition was observed to be the dominant stabilization mechanism, and NTC chemistry determines the stabilization point in mixture fraction space. Conversely, at 1100 K, the kinematic balance between the premixed flame propagation velocity and the incoming flow velocity becomes the dominant stabilization mechanism, and the classical triple flame structure was observed. Extended stabilization regimes, in terms of increasing boundary temperature, are therefore identified, including frozen flow, kinetically stabilized, autoignition-propagation-coupled stabilized, kinematically stabilized, and burner stabilized regimes.