An experimental and kinetic modelling study of NH3 + H2 + N2 + O2 flames : Laminar burning velocity under unconventional conditions and a novel approach for flammability limit determination
(2027) In Fuel 428.- Abstract
Ammonia (NH3) is a promising carbon-free fuel, and hydrogen (H2) enrichment is frequently employed to enhance its low reactivity. This study investigates the laminar burning velocity (SL), a fundamental combustion property, of NH3 + H2 flames under ultra-lean and ultra-rich conditions via oxygen (O2) enrichment strategy at 1 atm and 298 K. Experimental measurements and simulations using five kinetic models (namely Konnov, Stagni, Han, NUIG, and KAUST) were carried out, where both H2 and O2 enrichment significantly enhance the reactivity of NH3, enabling SL determination at extreme equivalence ratios (from ϕ = 0.3 to 1.7). It was... (More)
Ammonia (NH3) is a promising carbon-free fuel, and hydrogen (H2) enrichment is frequently employed to enhance its low reactivity. This study investigates the laminar burning velocity (SL), a fundamental combustion property, of NH3 + H2 flames under ultra-lean and ultra-rich conditions via oxygen (O2) enrichment strategy at 1 atm and 298 K. Experimental measurements and simulations using five kinetic models (namely Konnov, Stagni, Han, NUIG, and KAUST) were carried out, where both H2 and O2 enrichment significantly enhance the reactivity of NH3, enabling SL determination at extreme equivalence ratios (from ϕ = 0.3 to 1.7). It was found that the model by Han reproduces the experimental data best across all conditions investigated. A novel method for identifying flammability limits (FL) using non-adiabatic flame simulations is proposed, based on deviations from the linear relationship between lnSL and 1/Xu, where Xu represents the sum of mole fractions of fuel and O2 in the unburnt mixture. This approach proves to be computationally robust as it can find FL easily with low computational uncertainty, achieved through intrinsic error attenuation by a factor Xu,limt2≪1. The methodology was applied to NH3 + H2 + N2 + O2 flames over a wide range of conditions, yielding FL predictions consistent with experimental data from the literature. It is also noticed that the variations in FL determination due to kinetic model selection were significantly smaller than discrepancies in SL predictions, and brute-force reaction sensitivity analysis also reveals FL sensitivities are approximately 12 % of those for SL. An uncertainty assessment framework was developed, considering the computational noise and the uncertainties from kinetic model selection, e.g., a ϕ = 0.3 flame (60 %NH3 + 40 %H2 + O2 + N2) exhibited a total relative FL uncertainty of 2.1 % using the Han’s model. Recommendations were provided to improve FL determination accuracy, and the proposed methodology is expected to be broadly applicable to other fuel systems as a computational tool for FL prediction in combustion research.
(Less)
- author
- Han, Xinlu LU ; Wang, Zhihua and Konnov, Alexander A. LU
- organization
- publishing date
- 2027-01-15
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Ammonia, Flammability limit, Hydrogen enrichment, Laminar burning velocity, Ultra-lean
- in
- Fuel
- volume
- 428
- article number
- 140292
- publisher
- Elsevier
- external identifiers
-
- scopus:105041519288
- ISSN
- 0016-2361
- DOI
- 10.1016/j.fuel.2026.140292
- language
- English
- LU publication?
- yes
- id
- 49c06942-92f6-4796-874d-3f7ce0e758bf
- date added to LUP
- 2026-09-02 12:29:37
- date last changed
- 2026-09-02 12:30:02
@article{49c06942-92f6-4796-874d-3f7ce0e758bf,
abstract = {{<p>Ammonia (NH<sub>3</sub>) is a promising carbon-free fuel, and hydrogen (H<sub>2</sub>) enrichment is frequently employed to enhance its low reactivity. This study investigates the laminar burning velocity (S<sub>L</sub>), a fundamental combustion property, of NH<sub>3</sub> + H<sub>2</sub> flames under ultra-lean and ultra-rich conditions via oxygen (O<sub>2</sub>) enrichment strategy at 1 atm and 298 K. Experimental measurements and simulations using five kinetic models (namely Konnov, Stagni, Han, NUIG, and KAUST) were carried out, where both H<sub>2</sub> and O<sub>2</sub> enrichment significantly enhance the reactivity of NH<sub>3</sub>, enabling S<sub>L</sub> determination at extreme equivalence ratios (from ϕ = 0.3 to 1.7). It was found that the model by Han reproduces the experimental data best across all conditions investigated. A novel method for identifying flammability limits (FL) using non-adiabatic flame simulations is proposed, based on deviations from the linear relationship between lnS<sub>L</sub> and 1/X<sub>u</sub>, where X<sub>u</sub> represents the sum of mole fractions of fuel and O<sub>2</sub> in the unburnt mixture. This approach proves to be computationally robust as it can find FL easily with low computational uncertainty, achieved through intrinsic error attenuation by a factor Xu,limt<sup>2</sup>≪1. The methodology was applied to NH<sub>3</sub> + H<sub>2</sub> + N<sub>2</sub> + O<sub>2</sub> flames over a wide range of conditions, yielding FL predictions consistent with experimental data from the literature. It is also noticed that the variations in FL determination due to kinetic model selection were significantly smaller than discrepancies in S<sub>L</sub> predictions, and brute-force reaction sensitivity analysis also reveals FL sensitivities are approximately 12 % of those for S<sub>L</sub>. An uncertainty assessment framework was developed, considering the computational noise and the uncertainties from kinetic model selection, e.g., a ϕ = 0.3 flame (60 %NH<sub>3</sub> + 40 %H<sub>2</sub> + O<sub>2</sub> + N<sub>2</sub>) exhibited a total relative FL uncertainty of 2.1 % using the Han’s model. Recommendations were provided to improve FL determination accuracy, and the proposed methodology is expected to be broadly applicable to other fuel systems as a computational tool for FL prediction in combustion research.</p>}},
author = {{Han, Xinlu and Wang, Zhihua and Konnov, Alexander A.}},
issn = {{0016-2361}},
keywords = {{Ammonia; Flammability limit; Hydrogen enrichment; Laminar burning velocity; Ultra-lean}},
language = {{eng}},
month = {{01}},
publisher = {{Elsevier}},
series = {{Fuel}},
title = {{An experimental and kinetic modelling study of NH<sub>3</sub> + H<sub>2</sub> + N<sub>2</sub> + O<sub>2</sub> flames : Laminar burning velocity under unconventional conditions and a novel approach for flammability limit determination}},
url = {{http://dx.doi.org/10.1016/j.fuel.2026.140292}},
doi = {{10.1016/j.fuel.2026.140292}},
volume = {{428}},
year = {{2027}},
}