Development of a reduced multi-component combustion mechanism for a ammonia /diesel dual fuel engine by cross-reaction analysis

This study develops a four-component reduced mechanism with 333 species and 1934 reactions to predict combustion and emission characteristics of ammonia–diesel dual-fuel engines. The reduction process employed directed relation graphs (DRG), DRG with error propagation (DRGEP), and full species sensitivity analysis (FSSA). The reduced mechanism was validated using experimental data from the literature, including ignition delay times (IDT) and laminar flame speeds (LFS). Reaction pathway and species yield analyses were then conducted to explore how cross-reactions between ammonia and diesel affect diesel oxidation. The mechanism was further evaluated under RCCI combustion conditions, with ammonia energy substitution ratios of 20 % and 40 %. Results show that cross-reactions significantly influence ignition behavior, particularly at low-to-intermediate temperatures and with higher ammonia substitution. Moreover, cross-reactions notably alter the decomposition pathways of n-dodecane. At lower temperatures, including cross-reactions improves predictions of intermediate species from both fuels, while at higher temperatures, they have limited influence on species reactivity. The developed mechanism improves understanding of ammonia behavior in complex fuel systems by incorporating cross-reactions with key diesel surrogates. Striking a balance between accuracy and computational cost, it enables 3D CFD simulations of ammonia–diesel dual-fuel combustion, aiding in injection strategy design and emission control.