Enhanced burning rates in hydrogen-enriched turbulent premixed flames by diffusion of molecular and atomic hydrogen

Rieth, Martin; Gruber, Andrea; Williams, Forman A.; Chen, Jacqueline H.

doi:10.1016/j.combustflame.2021.111740

Cited by 75 publications

(31 citation statements)

References 41 publications

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“…This is because the spread of the source terms increases as the amount of ammonia is decreased, so while the average might seem lower than the cases with more ammonia, the maximum values are significantly higher (≈5 to 6 times). Moreover, for all lean cases, the consumption of hydrogen is higher for positive curvature due to the enhanced equivalence ratio in these regions, as detailed by Rieth et al [16]. However, this trend is flipped when the global equivalence ratio is increased.…”

Section: Curvature Effects On Flame Chemistrymentioning

confidence: 56%

“…Equations ( 4) and ( 5) are OH production reactions which involve H radicals and are enhancedfor positive curvature for the highest amount of ammonia, while the opposite is observed when the amount of ammonia is reduced. Although we know that hydrogen radicals are focused at the flame front with negative curvature values [16], the contradictory behaviour observed for the most amount of ammonia could be due to the fact that the H radical pool in the cases with the most ammonia is sufficiently low such that it is consumed before any diffusion processes enable focussing of the radical in the negatively curved flame front. Since the H radical is produced more in the flame fronts with positive curvature, due to the increase in the local equivalence ratio, the OH-producing reactions involving H radicals are higher for a positive curvature.…”

Section: Curvature Effects On Flame Chemistrymentioning

confidence: 97%

“…However, their study did not investigate cases with very high amounts of hydrogen (by mole fraction). Rieth et al [16] also studied curvature effects on the burning rates of hydrogen/ammonia/air flames. They concluded that the fast diffusing hydrogen radicals and molecules significantly impact the flame chemistry with respect to flame curvature.…”

Section: Introductionmentioning

confidence: 99%

“…Further research is required to quantify some of these effects and to study possible consequences in practical applications. Additionally, similarly to Rieth et al [16], the effect of diffusion parameters of molecular and atomic hydrogen needs to be studied for higher amounts of hydrogen in the fuel mixture to study the impact on the flame chemistry. The effect of explicitly including Soret and Dufour diffusion effects on the flame chemistry is also needed to understand implications of various diffusion models on the accuracy of current numerical models.…”

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confidence: 99%

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DNS Study of Spherically Expanding Premixed Turbulent Ammonia-Hydrogen Flame Kernels, Effect of Equivalence Ratio and Hydrogen Content

Mukundakumar

Bastiaans

2022

Energies

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In this study, 3D premixed turbulent ammonia-hydrogen flames in air were studied using DNS. Mixtures with 75%, 50% and 25% ammonia (by mole fraction in the fuel mixture) and equivalence ratios of 0.8, 1.0 and 1.2 were studied. The studies were conducted in a decaying turbulence field with an initial Karlowitz number of 10. The flame structure and the influence of ammonia and the equivalence ratio were first studied. It was observed that the increase in equivalence ratio smoothened out the small scale wrinkles while leading to strongly curved leading edges. Increasing the amount of hydrogen in the fuel mixtures also led to increasingly distorted flames. These effects are attributed to local increases in the equivalence ratio due to the preferential diffusion effects of hydrogen. The effects of curvature on the flame chemistry were studied by looking at fuel consumption rates and key reactions. It was observed that the highly mobile H2 and H species were responsible for differential rates of fuel consumption in the positively curved and negatively curved regions of the flame. The indication of a critical amount of hydrogen in the fuel mixture was observed, after which the trends of reactions involving H radical reactions were flipped with respect to the sign of the curvature. This also has implications on NO formation. Finally, the spatial profiles of heat release and temperature for 50% hydrogen were studied, which showed that the flame brush of the lean case increases in width and that the flame propagation is slow for stoichiometric and rich cases attributed to suppression of flame chemistry due to preferential diffusion effects.

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Section: Curvature Effects On Flame Chemistrymentioning

confidence: 56%

Section: Curvature Effects On Flame Chemistrymentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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DNS Study of Spherically Expanding Premixed Turbulent Ammonia-Hydrogen Flame Kernels, Effect of Equivalence Ratio and Hydrogen Content

Mukundakumar

Bastiaans

2022

Energies

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“…Rendering and 10 atm in a temporally-evolving shear layer configuration [39]; A CT scan of a chameleon [28] (Chameleon); A mechanical hand converted from surface meshes (MechHand); The SuperNova is provided by astrophysicists at the Oak Ridge National Laboratory. They are trained using GPU-based method and colored with green in Table 2.…”

Section: Volume Accuracymentioning

confidence: 99%