Abstract:

Diesel oxidation catalyst (DOC) upstream of catalyzed diesel particulate filter (CDPF) with additional diesel injection (hydrocarbon injection, HCI) were used to control the particulate matter (PM) emissions to meet stringent emission regulations for heavy-duty diesel vehicles. This study optimized the location of injector
upstream of DOC by evaluating the uniformity of HC distribution on the entrance of DOC. An HCI was used in active regeneration to enhance the exothermic heat of CDPF to initiate the soot regeneration. Numerical analysis was established for the combination of after-treatment technology DOC-CDPF, and a spray model for HCI was implemented into a commercial CFD code named AVL FIRE. Different locations and orientations of the injector were tested. The results show that injector location has a significant effect on the optimal mixing between the exhaust gas and injected hydrocarbon (HC). Optimum injector location is the injector located farthest from DOC, while the long distance between injector and DOC allows enough time for injected HC to form secondary droplets, as it mixes well with exhaust gas downstream. Using HCI upstream of DOC causes the exhaust gas temperature to increase and reaches 550 ℃ at the entrance of CDPF, which is enough to initiate active DPF regeneration.

Key words: vehicle exhaust emission, particulate matter (PM), hydrocarbon injection (HCI), catalyzed diesel particulate filter (CDPF), diesel oxidation catalyst (DOC), active regeneration