Developing Turbulence on the Propagation of Flames in Methane-Air Premixture

In spark ignition engines, initial flame kernel is wrinkled by a progressively increasing bandwidth of turbulence length scales until eventually the size of the flame kernel is sufficient for it to experience the entire turbulence spectrum. In the present study, an effective r.m.s. turbulence velocity as a function of time, estimated by integrating the non-dimensional power spectrum density function for isotropic turbulence, is utilized in the analysis of the statistical distribution of flame front curvatures and turbulent burning velocities of flames propagating in methane-air premixtures. The distribution of flame front curvatures shows these to become more dispersed as the effective turbulence velocity increases, and results in increased burning of premixtures. A decrease in the Markstein number also results in a further increase in curvature dispersion and enhanced burning, in line with the flame stability analysis.