Three-dimensional DNS with a pseudo-spectral, constant density code and simple (1-step) chemistry reproduced the previous findings that ignition occurs at the most-reactive mixture fraction (Mastorakos et al, Combustion and Flame, 1997, vol 109, p. 198) and at low scalar dissipation rates. The images below are results from simulations where initially, a thin slab of cold fuel at x=0.5 was exposed to hot air from both sides. The iso-surfaces of xMR are shown coloured according to local value of the temperature (left) and the scalar dissipation rate (right) and it is evident that a negative correlation exists. Further simulations are underway with complex chemistry.

Figure 1.  Temperature along xMR

Figure 2.  Scalar dissipation rate along xMR