NO Formation during Ignition of One Dimensional Laminar Flamelets

NO formation during ignition of combustible mixtures has been calculated in non– stationary two-dimensional systems by coupling the fluid flow and chemical reactions using “interactive flamelets”. The fluid flow was calculated by the PISO (Pressure– Implicit with Splitting of Operators) method to solve the Navier–Stokes equations. Further a convection–diffusion equation for the mixture fraction Z(x, y, t) has been solved to calculate the scalar dissipation rate χ, needed for the flamelet calculations. The one dimensional flamelet code solves the flamelet equation in the mixture fraction space. The stiffness of the system of equations describing the 1D non–stationary flamelets requires a fully-implicit calculation. It has been shown in the past, that Newton’s method, damped and modified, is suitable to solve this class of equations. A backward difference scheme (BDF) with automatic order selection strategies is utilized. The grid resolving the 1D–flamelet supports high accuracy by using a moving grid method. Back transformation of the calculated species mass fractions from the flamelet space gives a two dimensional distribution of all chemical species included in the large chemical system.