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This paper presents a new metallic catalyst substrate design that allows an integrated mixing behaviour and flow homogenisation within the substrate. In addition it offers a high mass transfer from the flow to the interior substrate surface. The design consists of corrugated walls with crosswise orientation of adjacent layers. The walls are permeable so that their high specific surface is directly accessible for the flow and consequently the length for diffusion is reduced and the mass transfer is enhanced. The crosswise corrugated design causes the intensive internal mixing of the flow within the substrate. Thereby local differences in velocity as well as in temperature and in concentration are equalized. Thus the new metallic substrate design concept offers homogeneous reaction conditions throughout the entire substrate. It allows a compact design and in case of a Diesel oxidation catalyst an additional soot reduction due to the design with permeable walls.

Published investigations on the calculation of pressure drop of diesel particulate filters consider the contribution of substrate, soot, channel flow and inertial effects at the inlet and outlet of the channels. The model presented in this work considers further contributions as the oil ash and additive ash and their effects on the DPF pressure drop. It is shown that different types of ash deposit which are caused by different driving cycles and different regeneration modes, will result in a significantly different pressure drop even at the same total amount of ash. It will be shown that in the case without soot load the ash deposit at the wall will result in a higher pressure drop than the same amount of ash being deposited at the rear end of the channels. It is also shown that at a higher soot load this behaviour will be inverted. In addition this work considers a variable permeability of the soot layer varying with the soot load of the filter.

A new concept for achievement of homogeneous flow distributions in catalytic converters and particulate traps is presented. New applications such as NOx-adsorbers, SCR-catalysts and diesel particulate filters call for more homogeneous flow distributions. The new concept of the progressive spin inlet serves for homogeneous flow distribution within a short inlet cone. A spin is imposed on the flow at the outer radius of the catalyst inlet using helical-type flow elements. It is essential that the centre part of the flow is almost free of spin. Best results can be obtained when the spin elements are designed to impose a progressive spin. The combination of a progressive slope angle and a progressive height serves for a relative minimum in pressure drop. It is shown, that the progressive spin element also proves very good results with eccentric arrangements of the catalyst inlet cone. The parameters are optimised using CFD-calculations.

Temperature control is essential for lean NOx-catalysts due to their limited maximum working temperature and their fast aging at high temperatures. Therefore, under high load efficient cooling is necessary. On the other hand light-up has to be fast, and cooling under low load has to be small. This can be achieved by switching the exhaust flow between an insulated tube at low temperatures and a cooling element at high loads. Conventional systems consisting of a valve with actuator are expensive and might fail during life-time operation. Therefore, a purely passive flow switch without moving parts was designed. At low exhaust velocities the exhaust gas moves through an insulated central tube, whereas at high exhaust velocities the exhaust gas flows through an outer tube which acts as a cooling element. The switching is characterized by the relative mass flow through the two ways as a function of total mass flow and temperature.