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Diesel urban buses and refuse trucks are part of the particulate emissions sources that affect city air quality. In order to reduce particulate pollutant emissions, a development program has been carried out based on a Euro 4 engine with a DPF technology. Currently, for Euro 4 compliance, SCR is the favoured technology. To avoid a completely new development, the Exoclean™ DPF system was located after the SCR. Catalyst. The severe operating conditions and the location of the DPF necessitated the development of an active system based on the association of a DPF and a Fuel-Borne Catalyst. A Renault Trucks MD9 engine was used. This work was funded by ADEME (French Agency for Environment and Energy Management). Due to severe stop and go duty cycles and the interest to fit the DPF downstream of the SCR, this study shows the benefit of using an active DPF with an FBC to ensure full regeneration even at low temperatures.

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.

To comply with ever more stringent emission limits, engineers are studying and optimising gasoline engine start-up and warm-up phases. Secondary air injection (SAI) represents one option to reduce emissions by post-oxidizing products of a rich combustion like HC, CO and H2. With this approach, the faster catalytic converter light-off allowed by the increase in exhaust temperature leads to a significant HC emissions reduction. All the mechanisms involved in post oxidation downstream of the exhaust valve are not well-known. In order to achieve substantial improvements, various SAI strategies were studied with a conventional PFI gasoline engine. Tests have been carried out both on steady-state running conditions and on transient warm-up phases at engine test bench. Various specific experimental devices and methodologies were developed. For example, the use of fast HC and temperature measurements is coupled with exhaust gas flow rate modeled with system simulation.