A triple flame is a partially premixed flame containing fuel-rich and fuel-lean premixed reaction zones and a nonpremixed reaction zone. The two premixed reaction zones form exterior wings and the nonpremixed reaction zone is established in between these two wings. The three reaction zones merge at a "triple point". The nonpremixed reaction zone is established in the region where excess fuel and oxidizer, from the rich and lean premixed reaction zones, respectively, mix in stoichiometric proportion. A fundamental understanding of triple flames is important from many scientific and practical considerations. Triple flames play an important role in the stabilization and liftoff of nonpremixed flames. They are also of fundamental importance in the reignition of turbulent mixtures. Triple flames might form when, after a local extinction due to excessive strain, the turbulence intensity decreases so that reignition can take place. In this investigation laminar triple flames that are stabilized on a Wolfhard-Parker slot burner are investigated. The flow consists of a rich mixture of methane and air emerging from the inner slot and a lean mixture from two symmetric outer slots. In this configuration the three reaction zones that characterize a triple flame can be clearly distinguished. Temperature measurements are performed using thermocouples, and C{sub}2{sup}*-chemiluminescence images are obtained. A detailed numerical model is employed to completely characterize the flame. It is based on a 17-species and 52-reaction mechanism. The numerical results are validated through comparisons with the experimental measurements. Our results focus on the detailed structure of a triple flame, the interaction between the three reaction zones, and the dependence of the flame structure on the initial velocities and mixture equivalence ratios. The dominant chemical pathways and the fuel-consumption efficiency are characterized. The lean premixed reaction zone (external wing) exhibits different features from the rich premixed reaction zone. In particular, it is characterized by strong HO{sub}2 formation and consumption reactions, and by relatively low CH{sub}4 consumption reactions.
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