Influence of the engine drop-to-idle process on regeneration temperature, filtration and morphology characteristics of diesel particulate filters

Abstract

As emission regulations become more stringent, the durability of diesel aftertreatment system is a concern in addition to its purification capacity. Under extreme circumstances, the engine may drop-to-idle (DTI) sharply, which can cause the diesel particulate filter (DPF) cracking and melting during active regeneration due to the excessive soot combustion heat. This study investigated the regeneration performance of cordierite DPFs during the DTI process, including temperature and emission characteristics. The temperature distribution is nonuniform, with the peak temperature occurring in the middle ring of the DPF monolith’s rear end. As the soot load reached 7 g/L, extensive DPF cracks were observed and the particle number (PN) emission exceeded the regulatory limit. The study also examined the evolution of the DPF's porous wall’s macro morphology and micro pore structure, finding that microcracks formed and the wall surface became rougher. The substrate’s bulk density, average pore diameter, and permeability decreased while the total pore volume, total pore area, tortuosity, and porosity increased. By analyzing temperature, filtration and morphology characteristics, this work provides a recommended soot mass limit (SML) for cordierite DPF, which is essential for developing a reliable regeneration strategy in diesel vehicle control systems. The findings also help with the optimization design of substrate and catalysts for manufacturers in terms of substrate material, filter geometry, cell density and catalyst coating.