| Summary: | 碩士 === 國立中山大學 === 機械與機電工程學系研究所 === 104 === Flame behaviors in a mesoscale one-stepped sudden-expansion channel are numerically investigated by a two-dimensional model without symmetry assumption at centerline. The channel expansion ratio β is equal to 2. The isothermal wall boundary condition (300K) is set to eliminate the wall-flame thermal interaction. It is found four flame behaviors: the steady mushroom-shaped flame, the steady tulip-shaped flame, the simple periodically oscillating flame and the complex periodic oscillating flame. The tulip-shaped flame is a transition among the steady and unsteady flame, and it is stable due to the wall-quenching effect. As the velocity of inlet raise, the simple periodic oscillating flame is caused by Landau-Darrieus flame instability. Meanwhile, the flame period time becomes longer with the mean velocity increase, and the flame axial length also longer. The existence of complex periodic flame is due to the interaction between Landau-Darrieus instability and hydrodynamic instability. I also change expansion ratio to find out flame behaviors under various mean velocity of inlet, and investigate the flame existence limit. In addition, another flame behavior, unsteady shaking flame, is observed. In this study, the flames exists because of the mean velocity if inlet, wall-quenching effect, flame instability and symmetry of the flowfield.
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