Abstract
Current developments in exhaust gas aftertreatment led to a huge mistrust in diesel driven passenger cars due to their NOx emissions being too high. The selective catalytic reduction (SCR) with ammonia (NH3) as reducing agent is the only approach today with the capability to meet upcoming emission limits. Therefore, the radio-frequency-based (RF) catalyst state determination to monitor the NH3 loading on SCR catalysts has a huge potential in emission reduction. Recent work on this topic proved the basic capability of this technique under realistic conditions on an engine test bench. In these studies, an RF system calibration for the serial type SCR catalyst Cu-SSZ-13 was developed and different approaches for a temperature dependent NH3 storage were determined. This paper continues this work and uses a fully calibrated RF-SCR system under transient conditions to compare different directly measured and controlled NH3 storage levels, and NH3 target curves. It could be clearly demonstrated that the right NH3 target curve, together with a direct control on the desired level by the RF system, is able to operate the SCR system with the maximum possible NOx conversion efficiency and without NH3 slip.
Highlights
Since 2015, the exhaust gas aftertreatment for diesel engine driven vehicles has been of particular interest in the realm of politics, society, and media
Slip causes a decrease in apparent NOx conversion and the latter does not represent the real x conversion); (e) the dosed NH3 concentration calculated by the NOx sensor signals up- and realNO
The storage curves right to the dashed line
Summary
Since 2015, the exhaust gas aftertreatment for diesel engine driven vehicles has been of particular interest in the realm of politics, society, and media. The NH3 -SCR is the only current DeNOx strategy for light and heavy-duty diesel engines with the capability to meet the current and upcoming emission legislations [1,2,3]. In this technique, aqueous urea solution of 32.5 wt % in water (diesel exhaust fluid = DEF, AdBlueTM , or AUS32 = aqueous urea solution) is injected into the exhaust to reduce toxic nitric oxides (NOx = NO + NO2 ) on special SCR catalysts. The formed ammonia adsorbs on the active sites of the SCR catalyst
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