Structure of High Intensity Turbulent Premixed Flames.

Abstract

Direct numerical simulations of hydrogen-air turbulent premixed flames propagating in two-dimensional homogeneous isotropic turbulence are conducted to investigate the effects of turbulence intensity on the structure of turbulent premixed flames. Detailed kinetic mechanism including 12 reactive species and 27 elementary reactions is used to simulate H2-O2-N2 reaction in turbulence. DNS are conducted for the cases of turbulent intensities of 10.0, 20.0 and 30.0 times of the laminar burning velocity. Turbulent burning velocity increases with the increase of turbulence intensity. The flame fronts for the case of lowest turbulence intensity can be classified in the regime of 'wrinkled laminar flame', whereas those for the cases of higher turbulence intensities show the characteristics of 'distributed reaction zone'. The mean flame thickness increases and the mean heat release rate decreases with the increase of turbulence intensity. However, for the higher intensity cases, variances of local flame thickness and heat release rate become large where the minimum local flame thickness decreases and the maximum local heat release rate increases with the increase of turbulence intensity. The local flame thickness and local heat release rate are well correlated with the tangential strain rate at the flame front.