Investigation on hydrogen/ethanol intrinsic flame instability

Abstract

The instability of laminar premixed hydrogen–ethanol flame was studied under different initial pressure, hydrogen ratio, and equivalence ratio conditions by using a constant volume combustion bomb. The unstable laminar premixed flame was measured using its thermal expansion ratio, flame thickness, effective Lewis number, and logarithmic growth rate of perturbation. The results demonstrated that the thermal expansion ratio and effective Lewis number were insensitive to initial pressure variation, but hydrogen ratio variation was significantly affected. The linear stability analysis indicated that when the hydrogen ratio increased, the premixed flame became hydrodynamically unstable; thermal diffusion effects later stabilized the flame as the hydrogen ratio increased. The critical radius and Peclet number decreased with the increased equivalence ratio of a 20% hydrogen mixture, but both parameters increased with an increased equivalence ratio under an 80% hydrogen ratio. Finally, the growth rate of perturbation decreased when the equivalence ratio increased.