Particle aggregation with simultaneous surface growth

Abstract

Particle aggregation with simultaneous surface growth was modeled using a dynamic Monte Carlo method. The Monte Carlo algorithm begins in the particle inception zone and constructs aggregates via ensemble-averaged collisions between spheres and deposition of gaseous species on the sphere surfaces. Simulations were conducted using four scenarios. The first, referred to as scenario 0, is used as a benchmark and simulates aggregation in the absence of surface growth. Scenario 1 forces all balls to grow at a uniform rate while scenario 2 only permits them to grow once they have collided and stuck to each other. The last one is a test scenario constructed to confirm conclusions drawn from scenarios 0-2. The transition between the coalescent and the fully-developed fractal aggregation regimes is investigated using shape descriptors to quantify particle geometry. They are used to define the transition between the coalescent and fractal growth regimes. The simulations demonstrate that the morphology of aggregating particles is intimately related to both the surface deposition and particle nucleation rates.

Numerical simulations of soot aggregation in premixed laminar flames

“…Recent studies, using numerical simulations of singleparticle trajectories [22,23] and of "lumped" properties with the method of moments [2], suggested a critical importance of interplay among all these individual processes-nucleation, coagulation, and surface growth. Moreover, these results suggested that the transition of spherical, coalescent growth into fractal-like objects is linked directly to the nucleation, as it supplies the abundance of very small primary particles.…”

“…In the present study we combine two techniques, the efficient stochastic particle collision algorithm [3,10] and the sterically-resolved collector-particle simulations [22,23]. In the following, we describe the numerical model, test the accuracy and authenticity of model predictions, and then perform a series of numerical simulations of time evolution of soot particles and their size distribution.…”

“…In recent applications of this general approach, particle dynamics were formulated in terms of one or two state variables like total particle volume and surface area [3,10,25,24]. In another development, a collector-particle technique was applied to investigate the transition between coalescent and aggregate growth [22,23], with the results incorporated [2] into the method of moments [6].…”

Reaction Dynamics of Carbon‐Centered Radicals in Extreme Environments Studied by the Crossed Molecular Beam Technique

“…36,37 These models suggest that the synthesis of small carbon-bearing molecules together with their radicals is linked to the formation of PAHs and to the production of soot and possibly fullerenes in hydrocarbon flames. [38][39][40][41][42][43] Various mechanisms have been postulated; those currently in favor are thought to involve a successive buildup of hydrogen-deficient carbon-bearing radicals and molecules via sequential addition steps of small hydrogen-deficient species such as carbon atoms (C), carbon clusters (C 2 , C 3 ), and carbon-bearing doublet radicals including ethynyl (C 2 H), cyano radicals (CN), and phenyl radicals (C 6 H 5 ). [44][45][46][47][48][49][50][51][52][53][54][55][56][57] Upon reaction with closed-shell hydrocarbons and their radicals, these elementary reactions do not only form more complex, closedshell hydrocarbons, but also extremely stable resonantly stabilized free radicals (RSFRs) and aromatic radicals (ARs) [1][2][3][4][5][6][14][15][16][58][59][60][61] In RSFRs, such as in the propargyl radical (C 3 H 3 ), the unpaired electron is delocalized and spread out over two or more sites in the molecule.…”

“…These high concentrations make them important reactants to be involved in the formation of soot and PAHs. [38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] Here, we review contemporary developments on crossed molecular beam studies that lead to the formation of highly hydrogen-deficient molecules acting as precursors to PAH-like species. In detail, crossed molecular beam reactions of carbon atoms (C), carbon clusters (C 2 , C 3 ), and carbon-bearing doublet radicals including ethynyl (C 2 H), cyano radicals (CN), and phenyl radicals (C 6 H 5 ) will be discussed.…”