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In urban areas, particulate emission from Diesel engines is one of the pollutants of most concern. As a result, particulate emission control from urban bus Diesel engines using particulate filter technology is being introducing in La Rochelle. The Diesel Particulate Filter (DPF) introduction on the existing urban bus fleet has been initiated by the CDA La Rochelle through a voluntary retrofit program. The class of urban bus to be retrofitted is based on EURO 1 and EURO 2 Diesel engines, using a standard European Diesel fuel with 300ppm of Sulphur content. In that case, the appropriated technology for DPF regeneration requires a very flexible strategy for DPF regeneration, such as the use of the Ceria-based Fuel-Borne Catalysts. The paper describes the practical approach developed to install and optimize the DPF System on the urban buses.

The impact of fuel hydrotreatment on Diesel exhaust emissions is investigated. Several fuels are formulated in a refining pilot unit. By progressively increasing the hydrotreatment severity, sulfur reduction is first achieved, followed by aromatic reduction and cetane enhancement. The operating conditions and the effect on fuel characteristics are detailed. The influence of this hydrotreatment on exhaust emissions of a light-duty prechamber engine is studied under both steady-state and transient conditions. In steady-state operation, a slight effect of fuel on CO and HC emissions appears which increases when the injection timing is retarded. No evidence of fuel influence on particulate emissions is found except for a sharp increase due to sulfate contribution for fuels with high sulfur content. The transient operation enhances the influence of fuel characteristics on pollutants.

This paper presents the main properties of a SiC diesel particulate filter bonded with specific ceramic oxides at a markedly lower sintering temperature than normal pure SiC DPF. The elasticity of the bond has been studied to have a good behavior to thermal shock permitting a larger cross section element and a reduction of the number of cement joints in the final monolith. That new product, manufactured at present is composed of seven square elements. Endurance tests have been carried out by laboratory bench testing in two commercial automobile diesel engines. The DPF pore size has been adjusted so that it may be catalyzed or impregnated.

In a few months, small two-stroke engines, which are used in two-wheel vehicles, will require the use of catalysis to achieve more stringent standard levels of emissions in the European Union. Such a kind of severe emission levels already exists in some countries and different catalytic gas after-treatment systems have already been studied. But in the most of cases, the principal aim was to fit in the existing exhaust lines of the corresponding vehicles. Thus, the catalyst parameters were chosen through criteria which were not mainly ‘catalytical’ criteria. Indeed, the performances of a catalytic system depend on many parameters, which are for example the position in the exhaust line, the dimensions of the monolith (diameter, length and cell density), the material (ceramic or metallic, thickness) or the precious metal formulation. An engine bench was equipped with a two-stroke engine and different configurations of the catalyst were considered.