Large Eddy Simulation Of Turbulent Partially-Premixed Flame Based On Redim Chemistry Table

In last two decades,large eddy simulation(LES)has become a promising tool in turbulent reacting flows investigation.However,LES of turbulent partially-premixed flame is still a challenging task.Recently,a new type of burner was designed by University of Sydney and Sandia National Laboratory to experimentally study turbulent partially-premixed flame,where fuel/air mixing pipe was recessed before main jet exit plane to provide inhomogeneous inlets.This burner emulates the key features of most of the practical systems,namely multi-stream mixing and existence of multiple combustion modes with addition of better flame stability with inhomogeneous inlets.The present study addresses the capabilities of REDIM-PFDF and m DTF-REDIM sub-grid scale(SGS)combustion models for this complex Sydney inhomogeneous burner flame cases.These two SGS models are based on the reaction-diffusion manifold(REDIM)technique,where modeling for turbulent-chemistry interaction is achieved with presumed filtered density function(PFDF)method and modified dynamic thickened flame(m DTF)approach in REDIM-PFDF and m DTF-REDIM SGS combustion models,respectively.The detailed chemical kinetics is reduced into a two-dimensional REDIM chemistry table which is using the mass fractions of CO₂(Y_CO2)and N₂(Y_N2)as the reduced coordinates.The top-hat FDF shape for Y_N2 is found to be a suitable option to deal with multi-stream mixing problem.In the m DTF-REDIM SGS model,on contrary to the classical DTF(c DTF)model,an additional lookup table is stored for the laminar flame thickness and flame speed parameters,which are the functions of corresponding mixture fraction values at flame locations.From the available database,FJ200-5GP-Lr75-57(FJ57),FJ200-5GP-Lr75-103(FJ103)and FA200-5GP-Lr75-45(FA45)flame cases are chosen for REDIM-PFDF model assessment,and the FJ57 flame case is chosen for simulation using m DTF-REDIM model.The main findings of the current work are as follows:The comparison between LES and experimental data shows the good agreement of mixture fraction,mass fractions of several species and temperature with the experimental data for REDIM-PFDF combustion model.Scatter plots and flame index analysis exhibit stratified premixed combustion near jet exit plane for inhomogeneous type of flame case(FJ57),augmenting the flame stability,while in near-homogeneous type of flame case(FA45)the diffusion type of combustion dominates near jet exit plane.Quantitative assessment of REDIM-PFDF SGS model for all the considered flame cases are done by the Wasserstein metric analysis.The Wasserstein metric calculations exhibited modeling error close to one standard deviation with respect to measurement for all the flame cases,showing the good performance of REDIM-PFDF combustion model.The FJ103 flame case in the experiments was observed close to local-extinction phenomenon.The instantaneous OH specie based distribution field and scatter plots analysis display the significant capture of local extinctions by REDIM-PFDF model.In the simulation of FJ57 flame case,the m DTF-REDIM SGS combustion model predicts a slight improvement for the mixture fraction,mass fractions of several species and temperature,compared to c DTF-REDIM model.Additionally,the Wasserstein metric analysis is conducted and shows m DTF-REDIM modeling error is less than one standard deviation with respect to measurement,demonstrating the good accuracy of it.