How does the dielectrophoresis affect the soot dendrite growth on resistive sensors?

Abstract

The European standards “Euro” limit the emission of several pollutants from thermal engine vehicles. The particle number (PN) and particulate mass (PM) emissions are specifically limited since 2011, hence modern Diesel engines are equipped with a Diesel particulate filter (DPF). On-board diagnostic (OBD) regulations impose to perform the self-diagnostic of the DPF. Nowadays, this diagnostic is done through a very simple backpressure monitoring, but the forthcoming steps will probably require a more sophisticated system, such as a resistive soot sensor. The aim of this study is to investigate the mechanisms leading to the formation of bridge-like soot deposits brought to light by scanning electron microscopy. A 2D model taking into account the aerodynamic transport and the electrostatic effects was used to improve our understanding of the soot deposition process. The model presented in this paper includes a force that has been neglected so far in previous works about resistive soot sensors: the dielectrophoresis. In this theoretical frame, this force affects particles motion in such a way that they tend to numerically build the bridge-like structures that are observed experimentally. Simulation shown that the dielectrophoresis mainly impact large particles – over 150 nm diameter.