A Priori Testing of Flamelet Generated Manifolds for Turbulent Partially Premixed Methane/Air Flames |
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Authors: | W J S Ramaekers J A van Oijen L P H de Goey |
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Institution: | (1) Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94550, USA; |
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Abstract: | To reduce high computational cost associated with simulations of reacting flows chemistry tabulation methods like the Flamelet
Generated Manifold (FGM) method are commonly used. However, H2, CO and OH predictions in RANS and LES simulations using the FGM (or a similar) method usually show a substantial deviation
from measurements. The goal of this study is to assess the accuracy of low-dimensional FGM databases for the prediction of
these species in turbulent, partially-premixed reacting flows. It will be examined to what extent turbulent, partially-premixed
jet flames can be described by FGM databases based on premixed or counterflow diffusion flamelets and to what extent the chosen
molecular transport model for the flamelet influences the accuracy of species mass fraction predictions in CFD-simulations.
For LES and RANS applications a model that accounts for subgrid fluctuations has to be added introducing additional errors
in numerical results. A priori analysis of FGM databases enables the exclusion of numerical errors (scheme accuracy, convergence) that occur in CFD simulations
as well as the exclusion of errors originating from subgrid modeling assumptions in LES and RANS. Four different FGM databases
are compared for H2O, H2, CO, CO2 and OH predictions in Sandia Flames C to F. Species mass fractions will be compared to measurements directly and conditioned
on mixture fraction. Special attention is paid to the representation of experimentally observed differential diffusion effects
by FGM databases. |
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