Dynamic behavior of splitting flames in a heated channel
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Flame-propagation dynamics with dual peaks in a heated microchannel is predicted by employing a thermal-diffusive model taking into account two reactants. After auto-ignition, the flame immediately splits into two reaction fronts with different luminosities. One front propagates upstream, whereas the other moves downstream, and finally they both extinguish. After some delay, the process is repeated, and reignition of the fuel-air mixture is induced by hot walls. It is also shown that the commonly used infinitely thin reaction zone model, which has no reactant concentration dependence, is not capable of capturing this phenomenon. The splitting flame dynamics with dual fronts is confirmed by photographs taken with a high-speed digital video camera in experimental investigations with a propane-air mixture. The experiments reveal interesting details, namely, coexistence of triple reaction peaks during the process of propagation of splitting flames is observed, and the flame splitting phenomenon occurs twice in one extinction-ignition period.
Key wordsmicroscale combustion splitting flames repetitive extinction and ignition
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