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Porous honeycombs filters have been widely used for diesel particulates filtration in passenger cars applications. In all current DPF applications, filter lifetime and design are dictated by the need to store non combustible ash generated at the exhaust. Therefore, improving the ash storage capacity of a filter appears as a major step towards the development of maintenance free DPF systems. This paper describes a new filter design that was developed to optimize ash storage volume. Numerical simulations and roller bench tests have been performed in order to compare the performances of this new filter to commercial honeycomb filters.

Ceria-based fuel-borne catalysts have been used to promote regeneration of the DPF, by lowering the soot-combustion temperature and favoring propagation of the combustion process throughout the soot layer, and thus to ensure durability of DPF efficiency over the EURO 4 standard limits. Since the market introduction of the PSA Peugeot Citroën DPF System for series applications, extensive works have been done to improve and simplify the DPF technology. A new enhanced ceria-based fuel-borne catalyst has been designed and developed to limit the DPF system maintenance. This paper proposes comparative studies of two different Ceria-based fuel-borne catalysts for DPF regeneration, particularly focussing on the enhanced catalytic activity of soot combustion: correlation between soot combustion and oxygen buffering is proposed to explain difference in catalytic activity, while catalytic activity on NOx species is not affected.

EHC design and engine operation requirements for a battery powered EHC-cascade were investigated using flow rig, engine dynamometer and vehicle evaluations. Low mass and Pd-coated heater elements and light-off converters are recommended for optimum light-off performance. Raising the heating power improves light-off. However, battery powered systems are limited to 1.5 kW. Rich engine operation combined with an excess of secondary air results in high exothermic energy output. The benefit of additional heating and the impact of cascade position (close coupled or underfloor) are closely related to the test cycle. ULEV limits were achieved using a MY 91 vehicle without upgrades in engine control.

The unsteady flow effects of a Close-Coupled Converter (CCC) are investigated. The aim is to improve the catalytic efficiency by uniformly utilizing the entire converter volume. Experimental and computational methods were used to evaluate the differences between unsteady and steady-state flow. Catalytic converters placed close to the engine have individual inflow pipes from each cylinder and suffer extreme filling and emptying processes. There is severe interaction of the pulsating exhaust flows. A wide range of engine operating points were studied at different engine speeds and load conditions. Also described is the influence of the gas pulsation on the conversion characteristics.

The “Multiple Disc Converter” is an innovative concept. In comparison to conventional catalytic converters, it is significantly less expensive and more compact, at identical conversion efficiency and durability. The catalytic substrate consists of 4 to 5 cylindrical ceramic discs with 62 cells/cm2 (400 cells/inch2). These are assembled in a sheet metal casing, without gaps between the discs, and angularly offset to each other. The flow through the channels is interrupted at the contact surfaces of the individual discs. Hence, the restarted turbulent flow intensifies the transverse mass transfer. Further, the uniformity of the exhaust gas flow is improved, particularly in the first discs. Thus, the conversion of emissions is improved and the durability extended. When the conversion is maintained at the level of conventional converters, then the converter volume can be substantially reduced using the same specific catalyst loading.