Taking diesel oxidation catalyst (DOC)

catalyzed diesel particulate filter (CDPF)

selective catalytic reduction (SCR) catalyst

and ammonia slip catalyst (ASC) as objects

the performances of DOC-CDPF-SCR-ASC and DOC-SCR-CDPF aftertreatment system configurations were compared on an engine test bench with several test cycles

including NOx onversion efficiency

NH3 slip

N2O emission

particle mass (PM) and particle number (PN) emission

and CDPF passive regeneration. The results show that these two kinds of configurations almost have the same effect of PM and PN emission reduction. The DOC-CDPF-SCR-ASC configuration has a better NOx conversion efficiency and CDPF passive regeneration performance. For this configuration

the CDPF has a regulating effect on the NO2 / NOx ratio at the inlet of the SCR catalyst

which can improve the SCR conversion efficiency

and the mean temperature of the SCR catalyst of this configuration is very close to that of the DOC-SCR-CDPF configuration due to the heat release of passive regeneration and NO oxidation in the CDPF. For the DOC-SCR-CDPF configuration

the CDPF can play a role of ASC and lead a lower NH3 slip

but it will produce a certain amount of NO2 and N2O emission.