Kim, K., Mital, R., and Higuchi, T., "An Investigative Study of Sudden Pressure Increase Phenomenon Across the SCR on Filter Catalyst," SAE Technical Paper 2016-01-2319, 2016, doi:10.4271/2016-01-2319.
In the previous research1), the authors discovered that the sudden pressure increase phenomenon in diesel particulate filter (DPF) was a result of soot collapse inside DPF channels. The proposed hypothesis for soot collapse was a combination of factors such as passive regeneration, high humidity, extended soak period, high soot loading and high exhaust flow rate. The passive regeneration due to in-situ NO2 and high humidity caused the straw like soot deposited inside DPF channels to take a concave shape making the collapse easier during high vehicle acceleration.It was shown that even if one of these factor was missing, the undesirable soot collapse and subsequent back pressure increase did not occur. Currently, one of the very popular NOx reduction technologies is the Selective Catalytic Reduction (SCR) on Filter which does not have any platinum group metal (PGM) in the washcoat. This work investigated the possibility of sudden pressure increase due to soot collapse in SCR on FilterAbsence of PGM prevented any in-situ NO2 formation in SCR on Filter. The passive regeneration in this case did not create the gap between the soot layers and filter wall that was observed previously with the catalyzed DPF. Consequently, the concave shape of soot under high humidity and subsequent soot collapse causing sudden pressure rise in the SCR on Filter were not observed.