A numerical study of soot aggregate formation in a laminar coflow diffusion flame

Journal Article · Sun Mar 15 00:00:00 EDT 2009 · Combustion and Flame

DOI:https://doi.org/10.1016/J.COMBUSTFLAME.2008.10.022· OSTI ID:21147122

Zhang, Q; Thomson, M J ^[1]; Guo, H; Liu, F; Smallwood, G J ^[2]

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1. Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario, M5S 3G8 (Canada)
2. Institute for Chemical Process and Environmental Technology, National Research Council of Canada, Building M-9, 1200 Montreal Road, Ottawa, Ontario, K1A 0R6 (Canada)

Soot aggregate formation in a two-dimensional laminar coflow ethylene/air diffusion flame is studied with a pyrene-based soot model, a detailed sectional aerosol dynamics model, and a detailed radiation model. The chemical kinetic mechanism describes polycyclic aromatic hydrocarbon formation up to pyrene, the dimerization of which is assumed to lead to soot nucleation. The growth and oxidation of soot particles are characterized by the HACA surface mechanism and pyrene-soot surface condensation. The mass range of the solid soot phase is divided into thirty-five discrete sections and two equations are solved in each section to model the formation of the fractal-like soot aggregates. The coagulation model is improved by implementing the aggregate coagulation efficiency. Several physical processes that may cause sub-unitary aggregate coagulation efficiency are discussed. Their effects on aggregate structure are numerically investigated. The average number of primary soot particles per soot aggregate n{sub p} is found to be a strong function of the aggregate coagulation efficiency. Compared to the available experimental data, n{sub p} is well reproduced with a constant 20% aggregate coagulation efficiency. The predicted axial velocity, OH mole fraction, and C{sub 2}H{sub 2} mole fraction are validated against experimental data in the literature. Reasonable agreements are obtained. Finally, a sensitivity study of the effects of particle coalescence on soot volume fraction and soot aggregate nanostructure is conducted using a coalescence cutoff diameter method. (author)

• OSTI ID: 21147122
• Journal Information: Combustion and Flame, Journal Name: Combustion and Flame Journal Issue: 3 Vol. 156; ISSN CBFMAO; ISSN 0010-2180
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
AEROSOLS
AIR
COALESCENCE
COMBUSTION KINETICS
DIFFUSION
DIMERIZATION
EFFICIENCY
ETHYLENE
LAMINAR FLAMES
Laminar diffusion flames
MATHEMATICAL MODELS
NANOSTRUCTURES
NUCLEATION
NUMERICAL ANALYSIS
OXIDATION
POLYCYCLIC AROMATIC HYDROCARBONS
PYRENE
SENSITIVITY ANALYSIS
SOOT
SURFACES
Sectional aerosol dynamics model
Soot aggregate formation
Soot coagulation efficiency
Soot coalescence
TWO-DIMENSIONAL CALCULATIONS
VELOCITY