Fine Flame Structure and Combustion Mechanism of Lean Turbulent Premixed Flames.

We observed the interaction between turbulence and combustion reaction near the lean flammability limit of a premixed flame supported by a hot burnt-gas stream, and elucidated the change in the fine flame structure with Damkohler number. A typical wrinkled laminar flame appeared when the equivalence fuel-to-air ratio of the mixture was 0.6, whereas for an equivalence ratio below the lean flammability limit (e. g., φm=0.4), the structure which looked like a distributed reaction zone was observed. This structure showed features similar to the distributed reaction zone, which was observed in a strongly turbulent shear layer, in many aspects of the statistics of fluctuating properties, such as temperature, ion current, and radical chemiluminescence.