Combustion Science and Technology, Vol.162, 223-234, 2001
Flame velocity of cellular flames at low Lewis numbers
The flame velocity of cellular flames at low Lewis numbers is numerically studied, based on the compressible Navier-Stokes equation including a one-step chemical reaction. The flame velocity of a cellular flame is always larger than that of a plane flame and increases as the Lewis number becomes lower. When the Lewis number is unity, the flame velocity is proportional to the surface area. When the Lewis number is lower than unity, on the other hand, the increment of the flame velocity is greater than that of the surface area. The local flame velocity increases (decreases) at a convex (concave) flame front with respect to the unburned gas. The increase in the flame velocity at a convex flame front exceeds the decrease at a concave one, which is due to the Arrhenius nonlinearity. Thus, the flame-velocity increment is greater than the surface-area increment at Lewis numbers lower than unity.