Large eddy simulation on the respective roles of integral length scale and turbulence intensity on turbulent premixed combustion

The effects of integral length scale () and turbulence intensity (^? ) on premixed combustion are studied using large eddy simulation. Three groups of lean CH4/air flames are carried out using the thickened flame model combined with a two-step reduced chemical mechanism. Two groups vary at constant ^? and the other group increases ^? from low to high while keeping unchanged. One of the cases is validated to available experimental data, showing good agreement for the flame-brush structure. The numerical results show that the increase in or ^? leads to a decrease in flame-brush height and an increase in flame-brush thickness and volume. The turbulent flame speed () will be enhanced by these two factors within the scope of our study. All the flame-brush structure data, including height, thickness, volume and area, and also collapse onto a single line when the turbulent Reynolds number is used as abscissa. The probability density function distributions of filtered thickened flame front curvature show that will be increased by and ^? through increasing the amount of large-scale and small-scale wrinkling structures respectively.