Differential diffusion effects inclusion with flamelet generated manifold for the modeling of stratified premixed cooled flames

CFD predictions of flame position, stability and emissions are essential in order to obtain optimized combustor designs in a cost efficient way. However, the numerical modeling of practical combustion systems is a very challenging task. As a matter of fact, the use of detailed reaction mechanisms is necessary for reliable predictions, especially for highly diffusive fuels. Unfortunately, the modeling of the full detail of practical combustion equipment is currently prohibited by the limitations in computing power, given the large number of species and reactions involved. The Flamelet Generated Manifold (FGM) method reduces these computational costs by several orders of magnitude without loosing too much accuracy. Hereby, FGM enables the application of reliable chemistry mechanisms in CFD simulations of combustion processes. In the FGM technique the progress of the flame is generally described by a few control variables. For each control variable a transport equation is solved during run-time. The flamelet system is computed in a pre-processing stage, and a manifold with all the information about combustion is stored in a tabulated form. In the present paper, the FGM model is implemented for the analysis of partially premixed non-adiabatic flames, including the effects of differential diffusion. Subsequently, a computational analysis of partially premixed non-adiabatic flames is presented. In this scope, a series of test simulations is performed using FGM for a two dimensional geometry, characterized by a distinctive stratified methane/air inlet, and compared with detailed chemistry simulations. The results indicate that detailed simulations are well reproduced with the FGM technique. Keywords Differential diffusion; Flamelet generated manifolds; Heat loss; Mixture fraction; Premixed