Zhou, Zhichao, Chen, Danan, Zhang, Junqing, Lin, Shusen, Li, Xing, Valera Medina, Agustin  ORCID: https://orcid.org/0000-0003-1580-7133 and Li, Jun
2026.
Preheat-enhanced laminar burning velocity and nitrogen-chemistry interactions of ammonia/n-heptane/air flames.
Applied Thermal Engineering
303
(3)
, 132402.
10.1016/j.applthermaleng.2026.132402
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Abstract
Co-combustion of ammonia with hydrocarbons introduces complex carbon‑nitrogen (Csingle bondN) chemical interactions that critically govern flame propagation and pollutant formation, yet the underlying kinetic mechanisms remain poorly elucidated due to a scarcity of reliable experimental data under elevated temperature. This study aims to resolve these Csingle bondN interactions by integrating laminar burning velocity (LBV) measurements with a purpose-built skeletal kinetic model that explicitly captures the cross-reactivity between carbonaceous and nitrogenous species. LBV of n-heptane/ammonia/air mixtures were experimentally determined using the externally heated divergent channel (EHDC) method over a wide parameter space: preheat temperatures of 400–500 K, equivalence ratios of 0.8–1.2, and ammonia fractions up to 70%. The updated skeletal mechanism incorporating a refined NH2 sub-mechanism and Csingle bondN coupling chemistry performs well under high ammonia blending ratios and elevated temperature conditions, achieving a 5% improvement in predictive accuracy for LBV. With increasing ammonia fraction, the LBV undergoes a two-stage reduction, declining near-linearly below 50% ammonia and transitioning to exponential decay at higher fractions. This shift is mechanistically linked to the changing kinetic dominance from carbon-driven to nitrogen-driven pathways. The LBV peaks under slightly rich conditions (Φ = 1.1), owing to the synergistic effects of adiabatic flame temperature and enhanced radical pooling involving carbon and nitrogen species. Raising the preheat temperature from 400 K to 500 K enhances the LBV by approximately 50%. Reaction pathway analysis further identifies HCN as the pivotal intermediate bridging the carbon and nitrogen chemistry, with its formation route switching from carbon-involving to nitrogen-dominated pathways as the equivalence ratio increases. By establishing a direct connection between macroscopic combustion parameters and the underlying kinetic interactions, this work provides both an experimental benchmark and a validated kinetic framework for advancing ammonia–hydrocarbon dual-fuel combustion models.
| Item Type: | Article |
|---|---|
| Date Type: | Publication |
| Status: | Published |
| Schools: | Schools > Engineering |
| Additional Information: | RRS applied |
| Publisher: | Elsevier |
| ISSN: | 1359-4311 |
| Date of First Compliant Deposit: | 10 September 2026 |
| Date of Acceptance: | 13 July 2026 |
| Last Modified: | 10 Sep 2026 13:00 |
| URI: | https://orca.cardiff.ac.uk/id/eprint/188317 |
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