LES-FGM modelling of non-premixed auto-igniting turbulent hydrogen flames including preferential diffusion
Tabulated chemistry methods are a well-known strategy to efficiently store the flows thermochemical properties. In particular, the Flamelet-Generated Manifold (FGM) is a widely used technique that generates the database with a small number of control variables. In order to build such a manifold, the...
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| Main Authors: | , , , |
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| Format: | Journal Article |
| Language: | English |
| Published: |
13-11-2024
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| Subjects: | |
| Online Access: | Get full text |
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| Summary: | Tabulated chemistry methods are a well-known strategy to efficiently store
the flows thermochemical properties. In particular, the Flamelet-Generated
Manifold (FGM) is a widely used technique that generates the database with a
small number of control variables. In order to build such a manifold, these
coordinates must be monotonic in space and time. However, the high diffusivity
of hydrogen can prevent such requisite.
To avoid the non-monotonicity of control variables (the progress variable, in
particular), one practical workaround is to perform the tabulation on
zero-dimensional (0D) reactors rather than on one-dimensional (1D) flamelets.
Various works already implemented and tested such 0D-based manifold, but mainly
in the context of spray engines, where most of the composition is lean and
information past the flammability limit is not relevant. The present work aims
at investigating, for the first time, the applicability of a tabulation based
on homogeneous reactors to study auto-igniting turbulent hydrogen jets.
It is shown that a combined use of homogeneous reactors at the lean side and
an extrapolation with 1D flamelets on the richer side is required to capture
both chemistry and diffusive effects accurately in pure hydrogen flames. Then,
this manifold is coupled to Large-Eddy Simulation (LES) of three-dimensional
turbulent mixing layers and evaluated against direct numerical simulation with
detailed chemistry. Good agreement is found, in terms of both ignition delay
and the following steady-state burning process. Further analyses are carried
out on statistics and modelling. In particular, the sensitivity of the LES
solution to filter width, turbulence-chemistry interaction and multidimensional
flame effects is investigated to provide new relevant insights on modelling
non-premixed auto-igniting turbulent hydrogen flames. |
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| DOI: | 10.48550/arxiv.2411.08505 |