An experimental investigation of particulate emission characteristics of catalytic diesel particulate filters during passive regeneration

Abstract

The catalytic diesel particulate filter (CDPF) can effectively reduce diesel particulate emissions, but its outlet particulate emissions increase significantly during active and passive regeneration. Understanding the particle emission characteristics and oxidation mechanism during CDPF regeneration is a prerequisite for seeking improvement measures and achieving near-zero emissions from diesel engines. This study focused on the particle emission characteristics during passive regeneration not previously detailed in the engine literature dedicated to catalytic diesel particulate filters. The commercial carbon black (Printex-U, PU) was utilized to replace diesel soot and loaded onto the CDPF substrate here. Experimental tests were conducted to investigate the effect of regeneration temperature and soot load on the CDPF response to exhaust particles during passive regeneration. The results showed that the diesel oxidation catalyst (DOC) reduced the particle number (PN) upstream of the CDPF device. In addition, the regeneration temperature and soot load altered the ratio of penetrating particles (PP), secondary particles (SP), and blown-out particles (BP), resulting in a complex particle emission profile in terms of particle concentration and size at the CDPF outlet. Moreover, the higher regeneration temperature enhanced the oxidation of the particulate matter and raised the particle number, while increasing the particle load enhanced the capture effect of incoming particles but also led to enhanced catalytic oxidation and destruction of the microstructure of the particle layer, thus increasing the discharged particle emissions.