Turbulent edge propagation speed of a lifted diffusion flame in turbulent mixing layer

Statistical properties of the leading fronts were investigated in a lifted diffusion flame established in a turbulent mixing layer in order to study the phenomenon of turbulent flame lift off. Evolution of the lifted flame stabilization process was numerically simulated by the flame hole dynamics model combined with the level-set method which enables us to trace the instantaneous flame edge location with the edge propagation speed given as a function of the local scalar dissipation rate. From the traced fronts of flame edges, temporal variations of the lift-off height, local flow velocity, and edge propagation speed were obtained to exhibit the statistical properties in the lift-off region. Based on these statistical results, a turbulent edge propagation speed was proposed as the average of propagation speed at the edges locally most protruding toward the upstream region and its temporal variation in the lifted flame is presented.