Influence of Flame Front Instability on Flame Propagation Behavior

This paper discusses flame acceleration due to flame instability mechanisms. In particular, the diffusive-thermal instability and hydrodynamic instability mechanisms are considered. The Sivashinsky equation is used to compute two-dimensional flame propagation behaviors, and the influence of each instability mechanism is separately considered. The effect of flame size on flame speed (accelerated due to the instability mechanisms) is particularly investigated. It is found that the flame propagation velocity (V_f) is independent of flame size under the influence of diffusive-thermal instability, whereas V_f increases with flame size under the influence of hydrodynamic instability. The fractal nature of the flame under the influence of hydrodynamic instability is confirmed based on the dependence of V_f on flame size. Fractal dimension is then calculated as a function of volume expansion ratio, the parameter that controls the hydrodynamic instability mechanism. An FFT analysis is conducted to further understand the flame’s fractal structure.