Effects of Iron Addition on the Collision of Polycyclic Aromatic Hydrocarbon Clusters: A Molecular Dynamics Study

Abstract

In this work, soot particle size distributions in iron-doped premixed ethylene flames are examined using scanning mobility particle sizer measurements. It is found that iron addition promotes the growth in soot particle size, and the enhanced particle coagulation is inferred to be an important reason. To support that, the influence of iron addition on the coagulation of polycyclic aromatic hydrocarbon (PAH) clusters, the analogue of incipient soot particles, is further investigated using molecular dynamics simulations. Based on the results of hundreds of binary head-on collision simulations, the collision between two coronene–Fe–coronene dimers is found to have a significantly higher coagulation efficiency than that between two coronene dimers. However, this enhancement effect weakens as the size of the PAH monomer increases. Although the coagulation efficiency can be increased by iron addition, the collision frequency is almost unaffected, as revealed from the binary off-central collision simulations. Moreover, the simulation results of coronene cluster growth via coagulation show that iron addition promotes coronene cluster growth, leading to larger cluster size, which may explain the larger soot particle size observed in iron-doped flames.

Combustion in a Sustainable World: From Molecules to Processes

“…The efficiency of carbon cluster growth from small polycyclic aromatic compounds can be enhanced by trace metals, such as iron, present in the combustion environment or in targeted combustion synthesis processes, as reported by Zhou et al for binary coronene collisions . The combination of two aromatics is an important step in particle inception mechanisms.…”

“…27,28 The efficiency of carbon cluster growth from small polycyclic aromatic compounds can be enhanced by trace metals, such as iron, present in the combustion environment or in targeted combustion synthesis processes, as reported by Zhou et al for binary coronene collisions. 29 The combination of two aromatics is an important step in particle inception mechanisms. In their theoretical investigation, Frenklach and Mebel explore the further transformations of a certain molecular structure, the E-bridge, which they have proposed as a key intermediate in the fusion of aromatic structures that precedes nucleation.…”

Molecular Dynamics Study on the Capture of Aluminum Particles by Carbon Fibers during the Propagation of Aluminum-Based Energetics

“…Reactive force field (ReaxFF), developed by van Duin and his coworkers, is employed in this work. ReaxFF offers a more realistic simulation of covalent bond formation and breaking while still being computationally tractable. − The potential energy E p of ReaxFF can be described by eq . E p = E bond + E over + E under + E lp + E val + E tors + E vdW + E coul in which the first six items are bond-order-dependent energy items: bond energy, overcoordination energy, under-coordination energy, long pair energy, valence angle energy, and torsion angle energy, respectively; the last two items are bond-order-independent items: van der Waals energy and Coulomb energy, respectively …”

Effect of Titania Nano-additives on Fine and Ultrafine Carbonaceous Emissions during Flame Combustion of Diesel

“…Additionally, there is better oxidation of soot particles at lower temperatures when fuel is blended with ferrocene additives. Similarly, soot particle size distribution for laminar pre-mixed burner-stabilized ethylene flames has been studied (Zhou et al, 2023). The experimental and computational study shows enhanced particle coagulation and the growth in soot particle size with the addition of ferrocene additives.…”