Extinction of Wrinkled Laminar Flame and Existence of Distributed Reaction Zone

The existence of two distinctly different combustion regimes are shown by the extinction limit. The effective Karlovitz number KaS was proposed to predict extinction. Using measured data, coming from the counterflow laminar flames, the laminar flame thickness and burning velocity were assessed. This flame thickness is much larger than the Zel'dovich characteristic length. Four different calculation methods of extinction Karlovitz number were presented. At the state of extinction of laminar flame, the effective Karlovitz number ranged around unity. On the other hand, in the opposed jet burner, impinging jets produce a strong tufbulence with small scale. In this burner, a stable annular turbulent flame is established at the stretch rate of 20 times greater than that of the laminar flame extinction. Although the distributed reaction zone is produced by extremely small scale eddies compared to the laminar flame thickness, there remains unclear how the transition occurs from the wrinkled laminar flame to the distributed reaction zone. In the present paper, a new model that includes the real flame property was suggested.