Intrinsic Instability of Premixed Flames at Sufficiently Low Activation Energy

Abstract

The intrinsic instability of premixed flames at sufficiently low activation energy was 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 wave number, i.e. the dispersion relation, and the average local burning velocity of a cellular flame. When the Lewis number was smaller (larger) than unity, the growth rate and the average local burning velocity decreased (increased) as activation energy became lower, because of the decrease of the Zeldovich number. When the Lewis number was unity, the growth rate decreased slightly at sufficiently low activation energy, and the average local burning velocity was almost constant. In addition, the dependence of the average local burning velocity on the Lewis number became weaker at sufficiently low activation energy.