Effect of Developing Turbulence and Markstein Number on the Propagation of Flames in Methane-Air Premixture

Abstract

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 rms turbulence velocity as a function of time, estimated by integrating the nondimensional power spectrum density (psd) function for isotropic turbulence, is utilized to analyze the statistical distribution of flame front curvatures and turbulent burning velocities of flames propagating in methane-air premixtures. The distributions of flame front curvatures show these to become more dispersed as the effective turbulence velocity increases, and result 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.