On flame-front instability at elevated pressures

Effects of pressure up to 3 atm on flame-front instability were numerically investigated for both linear and nonlinear growth stages at sub-unity and unity Lewis numbers. A sixth-order compact scheme and non-reflecting boundary conditions were used to capture the evolution of the flame front. Results show that in the linear instability growth stage, elevated pressure can extend the unstable range of flame-fronts and generate the fine flame cell structure. This effect can be qualitatively predicted by the theories when Le = 1.0; however the theories diverge at sub-unity Lewis numbers (e.g. Le = 0.7). In the nonlinear growth stage, the critical wave number (k(c)) from the linear dispersion relation can be used as a reference length scale for the evolution of the flame cell structure. Since elevated pressure increases the critical wave number, small flame cells appear over large flame cells (deep folds) at high ambient pressures. Furthermore, flame-front hydrodynamic instability is excited when the lateral domain is enlarged. (C) 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.