Thermophoretic Effects on Particles in Counterflow Laminar Diffusion Flames

Abstract

Abstract Thermophoresis, meaning particle drift down a local gas temperature gradient, is now known to be important to many combustion-related technologies. Until now, however, no direct experimental determinations of primary and aggregated particle thermophoretic diffusivities, αT D, in high temperature combustion environments have been reported. To perform such measurements, we selected a seeded laminar counterflow diffusion flame (CDF) operated at low strain-rate as a well-defined combustion system, offering at the same time a low velocity and high temperature gradient environment. We established a CH4/ O2Inert opposed jet diffusion flame in which the gaseous fuel/oxygen ratio, and the diluent flow rates were adjusted to obtain a flat, stable flame, approximately coincident with the gas stagnation plane (GSP). Particles fed to or formed on either or both sides of the GSP move toward this plane until the local axial velocity is exactly counterbalanced by the thermophoretic velocity. As a result of this ...