Laboratory studies of thermophoretic deposition for the reduction of diesel particulate emissions

摘要

Diesel exhaust particles emitted by modern heavy duty verhicle diesel engines are typically in the size range from about 10 to 300 nm.The deposition behaviour of these ultrafine soot particles is significantly influenced by thermophoresis in temperature gradients as they can be established in exhaust gas systems.In theoretical studies the thermophoretic coefficient K_(th) was predicted to be nearly independent of agglomerate particle size (Rosner and Khalil,2000).To avoid the well known disadvantages of conventional soot particle filter systems - high pressure drop and clogging by engine oil ash - filterless particle removal based on thermophoresis might be a suitable solution.The reduction of particulate emission based on temperature gradients in filterless deposition devices was up to now only numerically studied (Sasse and Nazaroff,1994).This study presents experiments on the thermophoretic deposition behaviour of agglomerated soot particles under well defined temperature gradient and flow conditions.Furthermore new model deposition structures whose particle removal efficiency is mainly caused by thermophoresis are experimentally characterized.