Investigations on the Impact of Urea-Dosing on Particulate Number Measurement for Heavy-Duty Applications
摘要
This paper addresses the influencing parameters of the generation of urea-based nano-particulates on top of engine-based soot emissions. Steadystate and transient engine operation studies show that the urea mass-flow and the exhaust temperature have the most significant impact on the formation of those extra particles. The number of those particulates correlates proportionally to the injected urea mass-flow with a major share of diameters below 23 nm. Injection parameters such as pressure or nozzle geometry show only a minor influence on the particle formation. To some extent the emissions are influenced by the aftertreatment layout with parameters like catalyst volume, cell density and technology selection. Various parameters associated with the urea injection show limited influence on the increase of particulate number. In a WHTC, the specific tailpipe particulate emissions increase up to a level of 2300% compared to a reference state without urea dosing. This needs to be critically considered especially in view of stricter exhaust emission regulations scheduled post Euro VI.