Large Eddy Simulation Study on the Turbulence and Flame Characteristics under Analogical Integral Scale and Turbulence Intensity of Turbulent Premixed Flames

Bunsen burner is a typical geometry for investigating the turbulence-flame interaction. In most experimental studies, only turbulence intensity u′ and integral scale l0 are used to characterize the turbulent flow field, regardless of the perforation geometry of perforated plates. However, since the geometry influences the developing process and vortex broken, the plate geometry has to be considered when discussing the flame-turbulence interaction. In order to investigate conditions at the same l0 and u′ using different geometries, large eddy simulation of CH4/air flames with dynamic TF combustion model was performed. The model validation shows good agreement between Large Eddy Simulation(LES) and experimental results. In the non-reacting flows, the Vortex Stretching of circular-perforated plate condition is always larger than that of slot-perforated plate condition, which comes from the stresses in the flow fields to stretch the vorticity vector. In reacting flows, at the root of the flame, the Vortex Stretching plays a major role, and the total vorticity here of circular-perforated plate condition is still larger(53.8% and 300% larger than that of the slot-perforated plate at x/D=0 and x/D=2.5, respectively). More small-scale vortex in circular-perforated plate condition can affect and wrinkle the flame front to increase the Probability Density Function(PDF) at large curvatures. The 3D curvature distributions of both cases bias to negative values. The negative trend of curvatures at the instant flame front results from the Dilatation term. Also, the value of the Vortex Stretching and the Dilatation at the flame front of circular-perforated plate condition is obviously larger.