Effects of detailed kinetics and thermodynamics of DEE+NH2 reactions on the ignition of ammonia blended with DEE

Recently suggested strategies for ammonia-blended combustion promote the interest in oxygenated hydrocarbon fuels . The development of combustion models for blended fuels is challenging and the cross-reactions are critical to the performance of the models. In this work, comprehensive ab initio thermodynamic and kinetic studies targeting diethyl ether (DEE) and its cross-reactions with NH 2 were carried out. Energy decomposition analysis was performed to study the source of energy difference between conformations. Direct dynamics calculations used variational transition state theory with an interpolated single-point energy method. The kinetic studies took into account dual-level corrections, pressure limit model, multidimensional tunneling approximation, variational, multi-path and multi-structural effects. The roles of various factors in determining the rate constants are elucidated and combustion models are updated and re-evaluated. The results demonstrate that the multi-structural effect dominate DEE-related kinetics and thermodynamics. The thermodynamic results of multi-structural methods align closely with the experimental data, significantly outperforming single-structural methods. The rate constants for the H-abstraction reactions by NH 2 are increased by a factor of 1.5 to 3.5 at high temperatures under the influence of the multi-structural torsional anharmonicity . The dual-level corrections should not be ignored for accurately evaluating multidimensional tunnelling and variational effects. The cross-reactions are found without pressure dependence above room temperature by PEM and LPL models and the multi-path VTST shows little effect. The accurate thermodynamic and kinetic data determined in this work play indispensable roles in better prediction of ignition properties and fuel conversion pathways. The initial conversion pathway of DEE through NH 2 has been significantly underestimated before. Notably, ab initio kinetics avoid artificially reduced rate constants of cross-reactions DEE+NH 2 used in previous works and provide a theoretically rigorous and rational insight into combustion chemistry . The current study fills a literature gap by studying the DEE+NH 2 reactions that are critical to the rational development of NH 3 /DEE co-firing models through detailed and high-level theoretical thermodynamic and kinetic studies . The kinetic studies took into account dual-level corrections, pressure limit model, multidimensional tunneling approximation, variational, multi-path and multi-structural effects. The accurate thermodynamic and kinetic data determined in this work play indispensable roles in better prediction of ignition properties and fuel conversion pathways. Detailed kinetic studies of this key cross-reactions replaced the artificially adjusted rate constants in previous mechanisms to develop a more rational combustion model for NH 3 /DEE blends.