Date of Award

2000

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

First Advisor

Tryfon T. Charalampopoulos

Abstract

Knowledge of optical properties and morphological characteristics of aggregated aerosols is important for pollution control, material synthesis through the aerosol route, oxidation of particulate matters, as well as understanding the mechanism of particulate formation and growth. However, the limitations of current light scattering theories as well as the lack of robust data inversion schemes render the complete characterization of the agglomerated structures difficult and time consuming. The objective of present work is to develop robust experimental and theoretical methods to characterize the aggregated aerosols from in-situ classical light scattering (CLS) as well as dynamic light scattering (DLS) measurements. In the context of classical light scattering, the following have been accomplished: (a) The theoretical formulation of light scattering for agglomerates consisting of Rayleigh particles developed by Lou and Charalampopoulos (LC) was evaluated through the use of reciprocity theorem and by comparison with the exact solution such as T-matrix method for aggregates; (b) A new robust criterion for determining the suitable number of orientations for calculating the averages of scattering properties has been introduced; (c) Based on the framework of LC, a data inversion scheme has been developed to infer the optical properties and the morphological parameters of combustion generated chain-like aggregates from classical light scattering measurements; (d) This methodology has been extended to incorporate the effect of polydispersity of the aggregates in the data inversion; and (e) Experimental investigations in iron pentacarbonyl seeded CO diffusion flames have been performed and good agreements with ex situ TEM analysis have been achieved using the data inversion scheme. In the context of dynamic light scattering, polarized and depolarized dynamic light scattering measurements have been conducted and the behavior of the experimental results has been analyzed. Moreover, the morphological parameters of chain-like agglomerates have been obtained from the measured diffusion coefficients of the agglomerates. It was demonstrated that the effects of the Gaussian term in the analysis of the measured correlation function may not be neglected.

ISBN

9780599906242

Pages

231

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