• Citer

Buoyancy effect in sooting laminar premixed ethylene flame

par Pejpichestakul, Warumporn ;Cuoci, Alberto ;Frassoldati, Alessio;Pelucchi, Matteo;Parente, Alessandro ;Faravelli, Tiziano
Référence Combustion and flame, 205, page (135-146)
Publication Publié, 2019-04-12

Article révisé par les pairs

• Accès en ligne
• Détails
• Contenu
• Statistiques

Résumé :

Polycyclic aromatic hydrocarbons (PAHs) are known as soot precursors, but their formation/consumption is not fully understood. A recent comprehensive experimental study of premixed laminar ethylene flame [23] investigated the transition from gas-phase to soot particles. The complex fluid dynamics of this system is taken into account to compare model predictions with experimental measurements and thus further validate a detailed kinetic mechanism of soot formation. The relatively low inlet velocity and the large distance between the burner and the stagnation plate lead to significant influence of buoyancy, which requires a 2-D simulation. The observed constricted (necking) flame structure can be reproduced only using a comprehensive 2-D simulation, which includes buoyancy effects, radiative heat losses, and thermal diffusion. Predicted axial gaseous and PAH species profiles obtained from the CRECK mechanism are in good agreement with the measurements, especially even-carbon-number aromatics. Reasonable agreement of the predicted soot volume fraction profiles is also observed. Additionally, simulation results from different literature kinetic mechanisms are also discussed to highlight similarities and differences. The largest discrepancies among the predictions of the mechanisms are observed for phenylacetylene, a key-species representing the first building block of PAHs synthesis in flames. A comprehensive analysis of relevant physical sub-models is also carried out in 2-D simulations. Additionally, predicted profiles from 2-D and 1-D simulations are compared. Following the literature, a 1-D simulation with imposed mass flux from the 2-D model was carried out to account for buoyancy effects. This approach provides an axial predicted flame temperature profile similar to the 2-D case. However, the predicted mole fraction profiles are quite different, especially for hydrogen and aromatics species because of the failure in accounting for the interplay of enhanced diffusion due to Soret effect, flame stretch, and large radial velocities in the proximity of the stagnation plane.