Experimental investigation of the role of soot volatile organic fraction in the regeneration of diesel filters

Abstract

This paper involves an experimental investigation of the role of the volatile organic fraction (VOF) adsorbed on the diesel particulate, in the initiation of regeneration of a SiC diesel filters installed on a modern diesel engine, run on catalytic additive-doped fuel. VOF adsorption-desorption and oxidation behaviour is mainly determined by performing a thermogravimetric analysis (TGA) of samples collected directly from a SiC filters installed on the engine running under low- and medium-speed and low- and medium-load conditions, as more representative of city driving. Based on the TGA analysis results, the percentage VOF content in soot was calculated and mapped as a function of engine speed and load in the range of investigation. The effect of adsorbed hydrocarbons on the regeneration behaviour was assessed by comparing regeneration experiments with the stepwise load increase for a filter loaded with soot at different VOF concentration levels. The appearance of a number of incidents of stochastic regeneration behaviour during loading at low exhaust temperatures with a relative high VOF content was observed and discussed. An effort was made to correlate regeneration rate with the VOF content in soot and the prevailing engine operation point during loading. This work aims at better understanding of diesel filter behaviour with modern diesel engines and also aims to support improved modelling of fuel-additive assisted regeneration by use of fuel additives at low temperatures (150-400 °C).