EXPERIMENTAL STUDY ON SCR EMISSION DURING DPF ACTIVE REGENERATION.

Diesel particulate filter (DPF) active regeneration causes exhaust gas temperatures to be around 600°C, which not only affects the urea injections, but it also seriously affects the efficiency of the selective catalytic reduction (SCR), resulting in many difficulties in the control of tailpipe nitrogen oxides (NO_x) emission and ammonia leakage. In this research, the influence of DPF active regeneration on SCR was experimentally studied with a bench. The influence of the DPF active regeneration on the SCR temperature, ammonia storage, urea injection, tail exhaust NO_x, and ammonia leakage was quantitatively analyzed under the World Harmonized Transient Cycle (WHTC). The results showed that the average temperature of the SCR rose from 245°C to 502°C. The high temperature affected the SCR conversion efficiency, especially when the temperature exceeded 550°C. The SCR conversion efficiency decreased significantly, and the tail NO_x changed from 0.12 g/kw-h to 0.65 g/kw-h. The sensitivity of the SCR conversion efficiency to the temperature was reduced, and the sensitivity to the space velocity was increased. When the temperature rose sharply, the dynamic follow-up of the ammonia storage and the ammonia leakage of the tailpipe were difficult to control. The concentration of the ammonia leakage was positively correlated with the space velocity. The control research results could provide a reference for SCR size design, control, and diagnosis strategies. [ABSTRACT FROM AUTHOR]