Study on oscillatory extinction dynamics mechanism of dimethyl ether spherical diffusion flame

The oscillatory extinction mechanism of micro-gravitational dimethyl ether (DME) spherical diffusion flame in hot- and cool-flame conditions was studied by numerical modeling with detailed chemistry and transport model. The results show that a stable self-sustaining cold flame can be established under microgravity conditions, and the cold flame reaction can significantly expand the flammability limit of flameout. Oscillation existed prior to the steady-state extinction turning point of either hot or cool flame. The oscillatory extinction of DME hot flame was governed by a single oscillatory mode, and its frequency (1 Hz or so) was independent of the ambient oxygen mole fraction. By contrast, the cool-flame oscillatory extinction was governed by dual mode of oscillation with distinct frequencies, and the oscillation period of the high-frequency mode significantly increased when approaching the extinction limit. Moreover, the dual oscillatory modes showed strong coupling interaction, so the cool-flame extinction was more complicated than hot flames. The sensitivity analysis indicated that the hot flame extinction was controlled by the competition reactions of high-temperature exothermicity/endothermicity and chain-branching/termination involving small molecules, and the cool flame extinction was controlled by competition of low-temperature branching and termination reactions in the negative temperature coefficient regime. © All Right Reserved.