The Effects of the Activation Energy on the Intrinsic Instability of Adiabatic and Non-Adiabatic Premixed Flames

抄録

The effects of the activation energy on the intrinsic instability of adiabatic and non-adiabatic premixed flames were studied by two-dimensional unsteady calculations of reactive flows based on the compressible Navier-Stokes equation. A sinusoidal disturbance 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 Le = 1, the activation energy had no effects on the instability of adiabatic flames. In non-adiabatic flames, the growth rate and burning velocity decreased as the activation energy increased, because the reduction of temperature at the flame front had a great influence on the flame instability at large activation energies. When Le < 1, the activation energy had much effects on both adiabatic and non-adiabatic flames. As the activation energy increased, the growth rate and burning velocity increased drastically, because of the increase of the Zeldovich number. In addition, the unstable behavior of cellular-flame fronts was observed at large activation energies. When Le > 1, on the other hand, the growth rate and burning velocity decreased as the activation energy increased. This was because that the stabilizing influence of diffusive-thermal effects became larger. The obtained results showed that the activation energy played an important role in the intrinsic instability of adiabatic and non-adiabatic premixed flames.