Two approaches to the simulation of silica particle synthesis

Abstract

In this paper, the flame synthesis of silica particles is studied. A model is presented that combines the detailed kinetics of gaseous species including the SiO2 precursor and the coagulation process of silica particles in a regime governed by Brownian motion. To describe the particle dynamics of the aerosol synthesis, two different numerical techniques are studied: first, the method of moments (MoM), and second, a new stochastic particle method (SPM), which results in a complete representation of the evolution of the particle size distribution function (PSDF). Both methods are economical regarding CPU time, which makes them attractive for modeling. This exact stochastic particle method is used to quantify the numerical error introduced by the closure of the moment evolution terms in the method of moments. It is found that the first three moments obtained with the MoM are in good agreement with the results from the SPM. The numerical error increases for moments of higher order. For validation of the model, a low pressure flame of H2/O2 diluted with Ar and doped with a SiH4 precursor is simulated and the results are compared with measurements. This comparison shows fair agreement, and a results from the literature obtained by a sectional method could be confirmed. Finally, the PSDF obtained from the SPM was used to produce a presumed shape fit of a lognormal distribution. Although based on one parameter only, the fit shows very good agreement with the exact PSDF.