Simulation of viscous flow aerosol sintering by three dimensional computational fluid dynamics

摘要

Industrial nanoparticle synthesis in the gas phase is realised by many different production processes,e.g.hot-wall tubular,plasma and flame reactors.For determination of the overall process many different mechanisms,such as nucleation,coagulation,surface growth and sintering have to be taken into account.Sintering itself consists of several mechanisms,as there are surface,volume and grain boundary diffusion,evaporation and recondensation,and viscous flow.Silica is one of the materials of great interest in ceramic particle processing.It is generally accepted that the predominant sintering mechanism for silica is viscous flow (Rumpf 1976).Hiram and Nir (1983) numerically investigated the surface tension driven coalescence of two equally sized initial spherical particles for different ratios of surface tension and viscosity.They numerically solved the Navier-Stokes equation with surface tension as the driving force.Van de Vorst et al (1994) conducted simulations of larger particle structures by a boundary element method but only with cylindrical symmetry in two dimensions.In the present work the sintering kinetics of silica nanoparticles is investigated by computational fluid dynamics (CFD) simulations in three dimensions using the volume of fluid method.Starting with the sintering of single particle contacts,sintering process is studied on fractal aggregates of different size and morphologies.