Effects of the activation energy on the intrinsic instability of premixed flames (Flame Instability at Low Activation Energies)

The effects of the activation energy on the intrinsic instability of premixed flames were studied by two-dimensional unsteady calculations of reactive flows, based on the compressible Navier-Stokes equation including a one-step irreversible chemical reaction. A sinusoidal disturbance with small amplitude was superimposed on a planar flame to obtain the relation between the growth rate and the wave number, i.e. the dispersion relation, and the burning velocity of a cellular flame generated by intrinsic instability. When the Lewis number was less than unity, the growth rate and burning velocity decreased as the activation energy became lower, because of the decrease of the Zeldovich number. When the Lewis number was unity, the growth rate and burning velocity were almost constant, and they decreased slightly at sufficiently low activation energies. In addition, the dependence of the growth rate and burning velocity on the Lewis number became drastically weaker at sufficiently low activation energies.