C–N–H chemistry, PAH growth and soot formation in non-premixed flames of ethylene/ammonia/hydrogen: A CFD study

• Mechanism comprising 125 species and 939 reactions for C 2 H 4 /NH 3 combustion. • Comprehensive validation against experimental data for ignition delay times, laminar flame speeds and species profiles. • Coupling of the mechanism with 2-D CFD to predict PAHs, soot and C–N–H species in diffusion flames. • Predictions of key pollutants and soot signals in non-premixed C 2 H 4 /NH 3 /H 2 flames alongside reaction pathway analysis. • Incorporation and predictions of previously missing nitrogenous species CH 3 CN and CH 2 CHCN formation in 2-D counterflow flame simulations. Ethylene/ammonia combustion in non-premixed flames presents critical challenges for predicting NO X , soot, and their precursors. This study elucidates fundamental mechanisms governing nitrogen oxide formation and soot pathways, essential knowledge for developing next-generation dual-fuel energy systems. To overcome these challenges, multidimensional computational fluid dynamics (CFD) simulations coupled with a kinetic mechanism comprising 125 species and 939 reactions are employed to reveal how pollutant formation is affected by the addition of NH 3 and H 2 fuels in ethylene flames. The mechanism is validated against experimental data, with C–N–H chemistry refined through sensitivity analysis. Additionally, a 2-D CFD model enhances prediction accuracy by capturing curtain flow effects absent in 1-D approaches, while the Moss-Brookes-Hall model predicts soot volume fractions under non-premixed ammonia and hydrogen doped flames. In 2-D co-flow flame simulations, the soot-inception-rate constant ( C a ) is identified for different cases to match predicted soot volume fractions. These improvements enable the first comprehensive predictions of CO, CH 4 , N-pollutants (NO, NO 2 ) and PAH/soot signals in non-premixed ethylene/ammonia/hydrogen flames, revealing essential C–N–H formation mechanisms.