Investigations Regarding Deposit Formation on Diesel Oxidation Catalysts 2020-01-1432
Deposit formation on components in the exhaust aftertreatment system is critical since RDE limits must be observed at any time. Besides, uncontrolled oxidation of carbonaceous deposits might damage the affected exhaust gas component. To comply with current and future emission standards diesel engines are usually operated with high EGR rates which leads to increased soot and hydrocarbon emissions what makes formation of carbonaceous deposits on EAT components more likely.
With this background, a research project was carried out that investigates influencing parameters and mechanisms of deposit formation on DOCs. Within the project a reference driving cycle was developed in order to create deposits within short time. In further endurance runs the driving cycle was modified and the changes of the deposits’ properties were analyzed. Furthermore, the engine was operated using different fuels, monoliths and engine operation modes. The thermal stability of the deposits is highly affected be the engine operation mode and the engine load within the driving cycle. On the other hand the thermal stability of the deposits does not change in a single endurance run within the periods covered by the investigations.
A sequence of typical stages of deposit formation could be found. Deposit formation is initiated at the catalyst inlet. This result is supported by 1D simulations and destructive testing of drill cores. Over the time there is an output or migration of existing deposits in single channels of the DOC, whereas growth of existing deposits occurs in other channels. In a later stage compact deposits may be built along the whole channel. These deposits consist mainly of separated soot particles.
Kevin Friese, Peter Eilts, Bernhard Lüers
Technical University of Braunschweig, FEV Europe GmbH