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The soot particle deposition in novel diesel particulate matter (DPM) catalyst structures was investigated on a lab-scale at a model test gas bench and in the exhaust system of a heavy duty diesel vehicle engine. Three different design approaches are compared. Under stationary conditions particle deposition is found to be caused by diffusional deposition, interception as well as particle transport to the structures' wall induced by exhaust flow accelerated around the corrugations. Diffusion leads to a pronounced deposition of small particles with mobility diameters smaller than 60 nm. The measured size-resolved filtration efficiency can be described by a phenomenological model derived from foam filtration.

The reduction of particulate emissions limits requires new tools for the tuning of engines and exhaust aftertreatment systems. Time-resolved monitoring of low soot emissions is a key feature for such developments. The paper describes an improved photoacoustic soot sensor, and presents its applications for the characterization of transient exhaust soot emissions before and after Diesel emission after-treatment systems. The detection limit of the unit is around 5 μg/m3 soot, which is two orders of magnitude better than conventional time-resolved transmission measurement. Additionally, a wide dynamic range of four orders of magnitude can be achieved without range switching. The photoacoustic signal is proportional to the soot mass, no significant cross-sensitivities to gaseous absorbers were detected.

The reduction of particulate emissions limits requires new strategies for the tuning of engines and exhaust after treatment systems. A non-blocking exhaust after treatment solution for HD vehicles to achieve the EuroIV emission limits has been developed which consists of a platinum oxidation catalyst and a stainless steel deposition structure with open channels for continuous soot storage and oxidation [1]. The significant advantages compared to standard particulate filters are caused by the open channel structure and characterized by a relatively low level of back pressure, selective separation of soot (EC) and penetrability for engine lubrication oil incineration ash. Extensive laboratory studies, including a screening of numerous promising deposition structure designs, led to a metal catalyst structure with microsphere coating. The processes dominating particle deposition could be determined, leading to a target-oriented optimization of the deposition structure.