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India is moving to Bharat Stage VI (BS-VI) from 2019 significantly lowering particulate mass (PM) , particle number (PN) and Nitrogen Oxides NOx emissions limits, as well as Carbon Dioxide CO2. BSVI’s particulate limits will require the use of diesel particulate filters (DPFs), which will need to operate properly under the driving conditions prevalent in India. Furthermore, NOx and CO2 emissions control will include advanced combustion modes with advanced fuel injectiontechnologies based on high pressure fuel injection and smaller injector holes, in combination with active NOx reduction measures. These advanced technologies will increase sensitivity to fuel quality, so will require tighter control of sulfur content, water contamination, fuel stability, lubricity and corrosion. These are real challenges for the robustness and durability of strategies developed for BS-VI and beyond.

Since Euro 5 standard, Diesel Particulate Filter (DPF) technology has been widely introduced in Europe and Fuel Borne Catalysts (FBC) provide a powerful solution to achieve regeneration in all driving conditions. Ongoing new emission regulation constraints of Euro 6.b (2014) and forthcoming Euro 6.c standard in 2017, that will reduce the gap between emissions during homologation and in real driving conditions, will demand the support of optimized FBC formulated with Deposit Control Additive (DCA). This paper presents the impact on DPF regeneration performance of advanced FBC with a sharp particle size distribution of reduced nanoparticle size diameter. Small particle size FBC gives enhanced DPF regeneration, allowing regeneration at lower temperature (i.e. improving fuel economy) but also lower dosing rates in fuel. Thus, this implies reduced filter ash content and an extended maintenance interval.

Diesel Particle Filters (DPFs) using a fuel-borne catalyst to assist filter regeneration provide a uniquely advantaged DPF technology. More than 5 million diesel passenger cars in the market today are equipped with this after-treatment system. Based on this extensive field experience, improvements have been made to the durability and maintenance requirements of this technology, and the total system cost has been optimized. Recently, a new fuel-borne catalyst, Eolys Powerflex™ (named new Fe-based FBC) has been developed to provide solutions that comply with current Euro 5 and forthcoming Euro 6 requirements that take into account both regulated emissions and optimization of CO₂ emissions. This paper presents the benefits of this optimized product. The soot oxidation activity of this new Fe FBC has been tuned to ensure fast and complete regeneration at low temperature and very low dosing rates in the fuel, thus reducing ash accumulation and improving the overall system durability.

Diesel urban buses as well as garbage trucks are part of the particulate emissions sources that affect the city air quality. Retrofit programs have developed Diesel particulate filters approaches in order to limit the particulate emissions in the cities. To fit the particular duty driving cycle requirements, a new active Diesel particulate filter (DPF) system is proposed to control the filters regeneration. The DPF system consists of: several particulate filter units; an oxidation catalyst placed in front of the filters; valves and jacks actuators allowing thermal insulation of the filters; control valves actuators; temperature and pressure sensors; and an electronic control unit and monitoring of the DPF system. Furthermore, in order to fully control the filters regeneration, an additional heat injection strategy, based on Diesel fuel injection over the oxidation catalyst, heats up the filters individually, according to the position of the insulation valves.

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.

Since the market introduction of the Diesel Particle Filter (DPF) system in serial applications in May 2000, more than 500,000 vehicles have been DPF-equipped. Tracking the serial production current situation, several themes for improvement have been identified, including system simplification to limit its total cost as well as proposition to optimize maintenance. The paper presents those upgrades that will be proposed in serial applications. Based on a DPF regeneration assisted by engine management systems in combination with the use of a Ceria-based fuel-borne catalyst, the first improvement is to limit the ash build up phenomenon of fuel-borne catalyst and then to limit the DPF clogging effect. In the first stage, catalytic activity of Ceria-based fuel-borne catalyst has been improved, by introducing Iron as a catalytic promoter.

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.

Since May 2000, PSA Peugeot Citroën has commercialized a wide range of diesel vehicles of different sizes (Peugeot 807, 607, 406 and 307; Citroën C8 and C5) equipped with a Diesel Particulate Filter (DPF) system using a Ceria-based Fuel-Borne Catalyst (FBC). More than 250000 vehicles have been sold in Europe. Based on extensive in-service feedback, an opportunity to further improve and optimize the technology was identified which will facilitate its extension to smaller passenger vehicles. The use of a more active FBC was identified as one of the key areas for improvement: with increased catalytic activity the FBC dosing rate is reduced and thus the rate of ash-build up in the DPF is limited. This could significantly extend the DPF interval maintenance. A new Ceria-based FBC (Ce-FBC) has been developed which demonstrates enhanced catalytic activity with limited exothermal peaks during DPF regeneration. This property is essential in preventing mechanical failure of the DPF.

A novel method for the evaluation of fuel-borne catalysts effect on DPF regeneration temperature is presented. The method is simple and allows for the in-situ determination of the regeneration temperature. It consists of the engine and trap preconditioning, the trap loading cycle and the regeneration phase. The repeatability of the method is better than ±1% of average value measured. The method is capable of distinguishing very low concentrations of the metal catalyst. The application of the method with different concentrations of the same catalyst does not require the use of fresh traps. For the evaluation of different catalysts however it is recommended to use a fresh trap, since the prescribed preconditioning is not capable of eliminating the effects of the previous additive.

In May 2000, PSA Peugeot Citroën launched, the Peugeot 607 HDi (High pressure Direct Injection) luxury sedan, the first series-production diesel passenger vehicle equipped with a Diesel Particulate Filter (DPF). The elimination of diesel particulate emissions is achieved by sequential trapping followed by regeneration of the DPF, assisted by a Ceria-based Fuel-Borne Catalyst (Ceria-FBC). In order to ensure reliable and durable DPF regeneration under all driving conditions, including the most demanding such as prolonged periods of idling and low speed driving, active and integrated system approaches are used. This technology was subsequently transferred to the diesel versions of the Peugeot 406 and the newly-launched Peugeot 307 and Citroën C5. This paper presents the functional and technical characteristics of the Ceria-FBC to fulfil specification requirements.

The present paper reports the use of a cerium-based FBC in association with a DPF for delivery applications, with long series of stop and go sequences. Two different field trials totaling at least 10,000 km each were performed using delivery conditions with an average of 100 stop-and-go per day and standard diesel fuel (350ppm of sulfur). The US application was done with a medium-heavy duty engine and the European application with a light duty engine. The efficiency of the DPF was determined by measuring both soot and inorganic product emissions. After the trials, the DPF were dismantled and retained ashes were characterized and their localization in the filter analyzed.

A test protocol, allowing for the evaluation of diesel particulate filters of different materials and of different sizes, located at various distances from the engine was developed. A total of 13 filter configurations were tested on a Euro I naturally aspirated diesel light duty truck with a fully passive trap system, utilizing only cerium-based additive in the fuel. It was proved that regeneration under constant urban driving conditions was always possible, at an exhaust gas temperature at the trap inlet in the range of 250 - 350°C. On a gravimetric basis, the efficiency of the traps tested concerning PM was in the order of 45 - 80% over the NEDC, depending on trap material and location along the exhaust pipe and reflecting the specific composition of the PM generated by the vehicle. No major effect on gaseous emissions (HC, NOx and CO) was observed.

A particulate trap with combined regeneration has been developed for use in light duty vehicles with diesel engines. This new system was tested first on an engine test rig. On-road vehicle tests are going on since August 1998. The results obtained clearly demonstrate the feasibility of this system. With this system trap regeneration has to be ensured under worst case conditions (exhaust gas temperature<400° C). To meet this requirement electrical heating in combination with a fuel-borne catalyst is applied. Different filter materials such as cordierite wall flow and silicon carbide monoliths were tested on the engine test rig. The paper reports on results from the engine test rig as well as from on-road vehicle testing. An overview about pre-heating and regeneration examples are given and energy balances are presented.