2026/04/16 by Tullio Viola, Nabiha Chaumeix, Andrea Comandini
Chemical Engineering · Physics and Astronomy · Engineering · #Advanced Combustion Engine Technologies #Advanced Chemical Physics Studies #Heat transfer and supercritical fluids
paper · doi:10.1016/j.combustflame.2026.114989
Soot formation still remains a contemporary challenge for the combustion community. Over the years, various theories have focused on pathways involving polycyclic aromatic hydrocarbons (PAHs). Recently, interest has shifted towards the gas-phase mechanisms of polyyne growth, which, alongside the PAHs, are believed to contribute to particle nucleation and growth through fast polymerization processes. This work proposes a new chemical kinetic model that incorporates these mechanisms to predict soot formation from shock tube experiments on acetylene pyrolysis. Acetylene was chosen as a reference intermediate for high-temperature combustion and as a key precursor for polyyne growth. The model, generated by the Soot Mechanism Automated Generator (SMAuG) framework recently built at ICARE, is composed of: i) the comprehensive PAH chemistry from ICARE gas-phase model; ii) an updated gas-phase C 2 H 2 sub-mechanism including pyrolytic kinetic pathways of C 2n H 2 polyacetylene species; iii) a new aromatic formation chemistry from acetylene and polyyne precursors; iv) implementation of activated soot precursors from the polyyne routes; v) complete chemistry of particle nucleation and growth. The model was validated against pyrolytic shock tube data, covering temperatures T 5 1603–1980 K, pressures P 5 16.7–18.2 bar, and C 2 H 2 mole fractions of 0.245% and 0.35%. The model accurately predicts the time-history profiles of soot volume fractions within a factor 2.2, and also kinetic parameters such as induction delay times and soot growth rates. Additional extensive validations were performed against literature data over a wide range of conditions. Kinetic analyses clarify the mechanisms behind acetylene soot formation, highlighting the conventional role of PAH pathways versus the newly proposed pathways under different conditions, as well as the influence of polyyne chemistry on particle growth.