Theoretical investigation of nitrogenated intermediates in ammonia/cyclopentane combustion via integration of a C₅-NH₂ mechanism reaction pathway

The NOx emissions of ammonia/hydrocarbon fuels are notably affected by C-N reactions. In this work, an updated C₅-NH₂ sub-mechanism was proposed and integrated into the kinetic model for ammonia (NH₃)/cyclopentane (C₅H₁₀) mixtures. The oxidation of C₅H₁₀/NH₃ was numerically investigated in a perfectly stirred reactor (PSR) over a temperature range of 300–2000 K. Two kinetic mechanisms were compared: a base mechanism and an updated version incorporating the new C-N sub-mechanism. The updated mechanism predicted a 16 % reduction in peak mole fractions of N₂O and a 5.4 % decrease in HCN levels compared with the base mechanism. Conversely, the mole fraction of NH₃ is anticipated to increase by 8 %. Reaction pathway analysis indicates that the updated mechanism exerted a higher inhibition effect on the production of N₂O than NO. Notably, the inhibitory effect of the C-N reactions on NO and N₂O formation is more pronounced at temperatures between 1000 and 1400 K. The generation pathways of NO/N₂O and HCN are analyzed with the rate of production (ROP) results, respectively. The formation of NO/N₂O is predominantly governed via the sequential reactions of NH₃ → NH₂ → NH → NO → N₂O and NH₃ → NH₂ → HNO → NO → N₂O.