Investigation of Adsorption Characteristics and Influencing Factors for Diesel Engine Exhaust Particles

Abstract

The adsorption process of diesel exhaust particles has a great influence on the particles. A single-cylinder diesel exhaust particle collection system was established to collect particle samples with different adsorption environment conditions, and the adsorption capacity of the samples was analyzed and characterized by an isothermal adsorption test; the change patterns of particle characteristics were investigated by the scanning electron microscope and thermogravimetric analyzer, correlation analysis of the factors influencing the adsorption process was performed. The results show that the particles have adsorption capacity and belong to the type of multilayer adsorption on porous media; the pore diameter is continuously distributed in the range of 8–80 nm with multiple peaks, which is the category of mesoporous and macroporous; the adsorption capacity of the sample particles increase with the increase of engine speed. Compared with the particles at the inlet of the exhaust pipe, the box-counting dimension (DB) of particles at the outlet increased, the content of water and soluble organic fraction (SOF) increased, the activation energy (E) decreased. Among the parameters affecting the adsorption process, the increase of hydrocarbons concentration contribute to the increase of particle adsorption and E reduction; the increase of the average temperature of the exhaust pipe inhibit the increase of the DB, and the increase of the temperature difference between the inlet and outlet facilitate the adsorption of water and SOF by the particles; the decrease of the adsorption time is one of the main reasons for the slowdown of the increase in DB; the average pore diameter had the greatest positive correlation with the amount of variation in the DB; the increase in specific surface area and pore volume of the sample particles was the dominant cause of the increase in adsorption capacity as well as the decrease in E.