On the radiative properties of soot aggregates part 1: Necking and overlapping

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DOIResolve DOI: http://doi.org/10.1016/j.jqsrt.2015.03.027
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Journal titleJournal of Quantitative Spectroscopy and Radiative Transfer
SubjectAbsorption spectroscopy; Aggregates; Carbon; Dust; Fractal dimension; Fractals; Global warming; Heat radiation; Morphology; Multiple scattering; Refractive index; Soot; Ultraviolet spectroscopy; Absorption and scatterings; Diffusion limited cluster aggregation; Discrete dipole approximation; Multiple scattering effect; Necking; Radiative properties; RDG-FA; Single scattering albedo; Agglomeration
AbstractThere is a strong interest in accurately modelling the radiative properties of soot aggregates (also known as black carbon particles) emitted from combustion systems and fires to gain improved understanding of the role of black carbon to global warming. This study conducted a systematic investigation of the effects of overlapping and necking between neighbouring primary particles on the radiative properties of soot aggregates using the discrete dipole approximation. The degrees of overlapping and necking are quantified by the overlapping and necking parameters. Realistic soot aggregates were generated numerically by constructing overlapping and necking to fractal aggregates formed by point-touch primary particles simulated using a diffusion-limited cluster aggregation algorithm. Radiative properties (differential scattering, absorption, total scattering, specific extinction, asymmetry factor and single scattering albedo) were calculated using the experimentally measured soot refractive index over the spectral range of 266-1064. nm for 9 combinations of the overlapping and necking parameters. Overlapping and necking affect significantly the absorption and scattering properties of soot aggregates, especially in the near UV spectrum due to the enhanced multiple scattering effects within an aggregate. By using correctly modified aggregate properties (fractal dimension, prefactor, primary particle radius, and the number of primary particle) and by accounting for the effects of multiple scattering, the simple Rayleigh-Debye-Gans theory for fractal aggregates can reproduce reasonably accurate radiative properties of realistic soot aggregates.
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AffiliationNational Research Council Canada (NRC-CNRC); Measurement Science and Standards
Peer reviewedYes
NPARC number21275835
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Record identifierde88b5b6-c98b-4544-8b04-cb2a11c3b514
Record created2015-07-14
Record modified2016-05-09
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