Unsteady modelling of a piloted methane/air jet flame based on the Eulerian particle flamelet model

Abstract

A piloted methane/air jet flame is numerically simulated by using both steady and unsteady flamelets. Unsteady calculations are performed in a postprocessing stage using Eulerian transport equations for passive scalars to describe the temporal evolution of the scalar dissipation rate, conditional on the stoichiometric mixture fraction. The influence of the number of particles, and the initial conditions of the fluid particle transport equations and unsteady flamelet equations on the predicted Favre-average species mass fractions are investigated. It is shown that the predictions obtained using unsteady flamelets are in closer agreement with the experimental data than the steady flamelet predictions, both for the minor and for the major species. Initialization of the probability of finding fluid particles over the fuel rich region and initialization of the unsteady flamelet profiles based on a piecewise-linear interpolation of the boundary conditions at the fuel, pilot flame and air inlets yield good agreement between the predicted and the experimental data. However, the OH and the NO mass fractions are overestimated.