Effect of C-N cross-reactions on combustion dynamics in ammonia binary blends

Zechang Liu, Xu He*, Guangyuan Feng, Chengyuan Zhao, Xiaoran Zhou, Zhi Wang, Qingchu Chen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

The application of ammonia (NH3) in the transportation sector presents a practical approach to steer the automotive industry towards a more eco-friendly and sustainable trajectory. The study examined the effect of C-N cross-reactions on laminar flame speed (LFS), ignition delay time (IDT), and species concentrations in binary NH3 blends using methane/ammonia (CH4/NH3), toluene/ammonia (C7H8/NH3), dimethyl ether/ammonia (DME/NH3), and n-heptane/ammonia (NC7H16/NH3) fuel mixtures. The research indicates that although C-N cross-reactions have a minimal impact on LFS of most blends, they significantly reduce the predictive precision of models for mixtures of C7H8/NH3. Furthermore, the existence of C-N cross-reactions diminishes the anticipated IDT of the combinations, and this influence becomes more pronounced as the initial temperature (T0) decreases. Furthermore, although C-N cross-reactions have a negligible impact on fuel species concentrations, they exert an impact on the concentrations of nitroic oxide (NO) and nitrous oxide (N2O). The mechanism by which C-N cross-reactions affect IDT and species concentrations is similar, mainly attributed to methyl (CH3) related C-N cross-reactions, which can be illustrated as: (1) C-N cross-reaction effects the concentration of CH3, which subsequently affects the concentration of CH3O. CH3O plays a vital role as a reactant for hydroperoxyl radical (HO2) generation in the intermediate temperature range (CH3O + O2 = CH2O + HO2), consequently exerting an impact on IDT; (2) the reaction NO + HO2 = NO2 + OH denotes the principal consumption reaction of NO, which is affected by HO2, consequently affecting the concentration of NO. (3) The H-abstraction reaction between NH2 and fuel promoted the primarily oxidation of fuel. This study concludes that limiting the inclusion to nine categories of reactions in C-N cross-reactions results in a considerable reduction in the complexity of the mechanism. This reduction significantly improves the predictive capacity of the model regarding combustion characteristics.

Original languageEnglish
Article number132061
JournalFuel
Volume373
DOIs
Publication statusPublished - 1 Oct 2024

Keywords

  • C-N cross reactions
  • Combustion characteristics
  • TRF/NH

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