Comprehensive linear stability analysis for intrinsic instabilities in premixed ammonia/hydrogen/air flames
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arXiv
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| Autores principales: | , , , , , , |
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| Formato: | Preprint |
| Publicado: |
2024
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| _version_ | 1866915195154071552 |
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| author | Lehmann, Terence Berger, Lukas Howarth, Thomas L. Gauding, Michael Girhe, Sanket Dally, Bassam B. Pitsch, Heinz |
| author_facet | Lehmann, Terence Berger, Lukas Howarth, Thomas L. Gauding, Michael Girhe, Sanket Dally, Bassam B. Pitsch, Heinz |
| contents | Two-dimensional direct numerical simulations of planar laminar premixed ammonia/hydrogen/air flames are conducted for a wide range of equivalence ratios, hydrogen ($\rm H_2$) fractions in the fuel blend, pressures, and unburned temperatures to study intrinsic flame instabilities (IFIs) in the linear regime. For stoichiometric and lean mixtures at ambient conditions, a non-monotonic behavior of thermo-diffusive instabilities with increasing ($\rm H_2$) fraction is observed. Strongest instabilities occur for molar ($\rm H_2$) fractions of 40%. The analysis shows that this behavior is linked to the joint effect of variations of the effective Lewis number and Zeldovich number. IFIs in ammonia/hydrogen blends further show a non-monotonic trend with respect to pressure, which is found to be linked to the chemistry of the hydroperoxyl radical $\rm HO_2$. The addition of $\rm NH_3$ opens new reaction pathways for the consumption of $\rm HO_2$ resulting in a chain carrying behavior in contrast to its chain terminating nature in pure $\rm H_2$/air flames. Theoretically derived dispersion relations can predict the non-monotonic behavior for lean conditions. However, these are found to be sensitive to the different methods for evaluating the Zeldovich number available in the literature. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2410_11466 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Comprehensive linear stability analysis for intrinsic instabilities in premixed ammonia/hydrogen/air flames Lehmann, Terence Berger, Lukas Howarth, Thomas L. Gauding, Michael Girhe, Sanket Dally, Bassam B. Pitsch, Heinz Fluid Dynamics Two-dimensional direct numerical simulations of planar laminar premixed ammonia/hydrogen/air flames are conducted for a wide range of equivalence ratios, hydrogen ($\rm H_2$) fractions in the fuel blend, pressures, and unburned temperatures to study intrinsic flame instabilities (IFIs) in the linear regime. For stoichiometric and lean mixtures at ambient conditions, a non-monotonic behavior of thermo-diffusive instabilities with increasing ($\rm H_2$) fraction is observed. Strongest instabilities occur for molar ($\rm H_2$) fractions of 40%. The analysis shows that this behavior is linked to the joint effect of variations of the effective Lewis number and Zeldovich number. IFIs in ammonia/hydrogen blends further show a non-monotonic trend with respect to pressure, which is found to be linked to the chemistry of the hydroperoxyl radical $\rm HO_2$. The addition of $\rm NH_3$ opens new reaction pathways for the consumption of $\rm HO_2$ resulting in a chain carrying behavior in contrast to its chain terminating nature in pure $\rm H_2$/air flames. Theoretically derived dispersion relations can predict the non-monotonic behavior for lean conditions. However, these are found to be sensitive to the different methods for evaluating the Zeldovich number available in the literature. |
| title | Comprehensive linear stability analysis for intrinsic instabilities in premixed ammonia/hydrogen/air flames |
| topic | Fluid Dynamics |
| url | https://arxiv.org/abs/2410.11466 |