• Journal of the Korean Institute of Gas
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• v.13 no.3
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• pp.33-42
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• 2009

A numerical analysis of reactive flow in a liftoff flame is accomplished to elucidate the characteristics of liftoff flame. To verify reliance of numerical calculation, the liftoff heights of liftoff flame for various fuel exit velocities are compared between the existing experimental research results and the present calculation results. The flame propagation velocity is conducted at the flow redirection point which is on a stoichiometric line ahead of flame front. This point was selected constant distance from triple point regardless of fuel exit velocity at the previous research. This causes considerable errors for the flame propagation velocity and scalar dissipation rate. The main issue of the present research is to establish the resonable method to select the redirection point and so that to clarify the relationship between flame propagation velocity and scalar dissipation rate, which is the core properties in a triple flame stability.

• 한국연소학회:학술대회논문집
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• 2004.11a
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• pp.85-90
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• 2004

We have presented characteristics of a transitional behavior from a premixed flame to a triple flame in a lifted flame according to the change of equivalence ratio. The experimental apparatus consisted of a slot burner and a contraction nozzle for a lifted flame. As concentration difference of the both side of slot burner increases, the shape of flame changed from a premixed flame to a triple flame, and the liftoff height is decreased to the minimum value and then increase again. Around this minimum point, it is confirmed a transition regime from premixed flame to triple flame. Consequently, the experimental results of the liftoff height, flame curvature and luminescence intensity showed that the stabilized laminar lifted flame regime is categorized by regimes of premixed flame, triple flame and critical flame. In the visualization experiment of smoke wire, the flow divergence and redirection reappeared in premixed flame as well as triple flame. Thus we cannot express the flame front of lifted flame has a behavior of triple flame with only flow divergence and redirection. To differentiate triple flame and premixed flame, ${\Phi}$ value of partially premixed fraction is employed. The partially premixed fraction ${\Phi}$ was constant in premixed flame. In critical flame small gradient appears over the whole regime. In triple flame, typical diffusion flame shape is obtained as parabolic distribution type due to diffusion flame trailing.