NUMERICAL SIMULATIONS OF A PREMIXED TURBULENT CONFINED JET FLAME USING THE FLAMELET GENERATED MANIFOLD APPROACH WITH HEAT LOSS INCLUSION

摘要

In the present paper a computational analysis of a confined premixed turbulent methane/air jet flame is presented. In this scope, chemistry is reduced by the use of the Flamelet Generated Manifold (FGM) method, and the fluid flow is modeled in a RANS context. In the FGM technique the reaction progress of the flame is generally described by a few control variables, for which a transport equation is solved during runtime. 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 implementation the reaction evolution is described by the reaction progress variable, the heat loss is described by the enthalpy and the turbulence effect on the reaction is represented by the progress variable variance. The turbulence-chemistry interaction is considered through the use of a presumed pdf approach. A generic lab scale burner for high-velocity preheated jets is used for validation. It consists of a rectangular confinement, and an off-center positioning of the jet nozzle enables flame stabilization by recirculation of hot combustion products. The inlet speed is appropriately high, in order to be close to the blow out limit. Flame structures were visualized by OH~* chemiluminescence imaging and planar laser-induced fluorescence of the OH radical. Laser Raman scattering was used to determine concentrations of the major species and the temperature. Velocity fields were measured with particle image velocimetry. The important effect of conductive heat loss to the walls is included in the FGM chemistry reduction method in a RANS context, in order to predict the evolution and description of a turbulent jet flame in high Reynolds number flow conditions. Comparisons of various mean fields (velocities, temperatures) with RANS results are shown. The use of FGM as a combustion model shows that combustion features at gas turbine conditions can be satisfactorily reproduced with a reasonable computational effort.