Chemical kinetic study of lean-burn and NO/N2O behaviors on ethanol/ammonia cracked gas

Xiangyu Meng; Menglan Miao; Xuanrui Zhang; Yuqiang Li; Wuqiang Long; Mingshu Bi

doi:10.1016/j.scitotenv.2025.178587

Chemical kinetic study of lean-burn and NO/N₂O behaviors on ethanol/ammonia cracked gas

Sci Total Environ. 2025 Jan 23:964:178587. doi: 10.1016/j.scitotenv.2025.178587. Online ahead of print.

Authors

Xiangyu Meng¹, Menglan Miao¹, Xuanrui Zhang¹, Yuqiang Li², Wuqiang Long³, Mingshu Bi¹

Affiliations

¹ School of Chemical Engineering, Dalian University of Technology, Dalian, Liaoning 116024, China.
² School of Energy Science and Engineering, Central South University, Changsha 410083, China. Electronic address: [email protected].
³ Institute of Internal Combustion Engine, Dalian University of Technology, Dalian, Liaoning 116024, China.

PMID: 39862498
DOI: 10.1016/j.scitotenv.2025.178587

Abstract

Ammonia (NH₃) holds promise as a carbon-free fuel. Blending it with highly reactive fuels could efficiently alleviate issues such as slow burning rates and narrow flammability ranges. Ethanol (C₂H₅OH) offers the advantage of carbon neutrality and has a high-octane rating. Ammonia cracking is an efficient way to on-line hydrogen generation, mitigating storage and transportation concerns. This work aims to research the combustion of ammonia/ethanol blends with ammonia cracking. To achieve highly accurate predictions for these fuel blends, a detailed combustion chemical kinetic mechanism with 126 species and 1453 reactions for NH₃, C₂H₅OH, H₂, and their blends was developed. This mechanism underwent extensive validation against experimental measurements reported in the literature, including laminar burning velocity (LBV) at initial temperatures ranging from 298 to 473 K, pressures from 1 to 5 atm, and equivalence ratios from 0.5 to 1.6, as well as ignition delay time (IDT) at initial temperatures from 820 to 2500 K, pressures from 1.2 to 60 atm and equivalence ratios from 0.3 to 1. Additionally, a simplified mechanism containing 73 species and 449 reactions was developed using a couple of mechanism reduction methods. The effect of adding ethanol on LBV was investigated under laminar burning conditions, and the decoupling of thermal, chemical, and transport effects was studied. Considering the complexity of fuel composition for the blends, a modified Metghalchi-Kech power law formula was performed, which exhibits a highly linear correlation with LBVs of the blended fuels when coupled with the sum of maximum mole fractions for OH/O/H/NH₂. Furthermore, NO and N₂O behaviors were also investigated for various fuel blends and initial conditions. It was found that the a higher NH₃ cracking ratio tends to help to reduce the NO generation, and thermal NO is higher at elevated initial temperature and pressure. N₂O is easily produced under lean-burn condition.

Keywords: Ammonia cracking; Ammonia/ethanol/hydrogen; Chemical kinetic modeling; LBV behaviors; NO and N(2)O characteristics.