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A particulate trap with additive supported regeneration is a very effective way of reducing soot emissions of diesel exhaust gas. Particulate traps presently available on the market clearly show that the regeneration process is the most important detail in particulate trap technology. In this specific case of particulate traps, active rare earth oxides are added into the fuel to produce an initial and almost continuous regeneration without external burners, resistance heating, etc., as is well known from other systems. It should not be forgotten that an externally initiated regeneration will always produce a temperature peak inside the soot collecting filter media which may destroy them. Such damage can be avoided by catalytically supported regeneration of particulate traps. In the presence of an active catalyst, an inorganic cerium compound, regeneration temperature will decrease from 550 to 600 deg. C normally to about 350 to 400 deg. C.

The paper reports on the results of a joint research program performed at Rhône-Poulenc and AVL concerning a passive trap system with Cerium (Ce) as a new patented fuel additive in conjunction with an engine management control system to increase the exhaust gas temperature for initiating regeneration under practically all engine application conditions. Investigations were carried out on a 12L DI/TCI HD diesel engine which meets the US94 emission standards. From the work done the most effective combination of the engine control measures has been established as an apprepriate solution to increase the exhaust gas temperature up to 400 deg. C. at minimum penalty with respect to emissions and fuel consumption. Furthemore, the influence of Cerium on engine-out emissions and fuel consumption has been investigated. It could be shown that by using Cerium, the fuel consumption improves on average by about 2 percent.

In the past, concentrated efforts were directed at developing a cost effective and reliable particulate trap, assisted by mechanical (burners) or electrical (heating elements) regeneration means. Although ceramic monolith filter developments have been straightforward, regeneration systems have proven to be problematic and costly. Therefore, these development efforts led to disappointing results. Using catalytic fuel additives to promote regeneration in a trap through lowering the incineration temperature of collected soot is an attractive alternative. This passive form of regeneration could be technically and economically advantageous for diesel applications by eliminating complex sensors and controllers required for regeneration systems in new installations as well as retrofitting older vehicles. A cerium based fuel additive was used to assist in regenerating particulate traps in diesel exhaust aftertreatment.

Exhaust gas recirculation (EGR) has long been used in gasoline and light-duty diesel engines as a NOx reduction tool. Recently imposed emission regulations led several heavy-duty diesel engine manufacturers to adopt EGR as part of their strategy to reduce NOx. The effectiveness of this technology has been widely documented, with NOx reduction in the range of 40 to 50 percent having been recorded. An inevitable consequence of this strategy is an increase in particulate emission, especially if EGR was used in high engine load modes. Selective catalytic reduction (SCR), a method for NOx reduction, is widely used in stationary applications. There is growing interest and activity to apply it to mobile fleets equipped with heavy-duty diesel engines. Results of this work indicate that SCR has the potential to dramatically reduce NOx in diesel exhaust. Reductions greater than 70 percent were reported by several including the Institute's previous work (SAE Paper No. 1999-01-3564).

The diesel engine has long been the most energy efficient powerplant for transportation. Moreover, diesels emit extremely low levels of hydrocarbon and carbon monoxide that do not require post-combustion treatment to comply with current and projected standards. It is admittedly, however, difficult for diesel engines to simultaneously meet projected nitrogen oxides and particulate matter standards. Traditionally, measures aimed at reducing one of these two exhaust species have led to increasing the other. This physical characteristic, which is known as NOx/PM tradeoff, remains the subject of an intense research effort. Despite this challenge, there is significant evidence that heavy-duty highway engine manufacturers can achieve substantial emission reductions. Many development programs carried out over the last five years have yielded remarkable results in laboratory demonstrations.

The invisible nanoparticles (NP)*) from combustion processes penetrate easily into the human body through the respiratory and olfactory pathways and carry numerous harmful health effects potentials. NP count concentrations are limited in EU for Diesel passenger cars since 2013 and for gasoline cars with direct injection (GDI) since 2014. The limit for GDI was temporary extended to 6 × 1012 #/km, (regulation No. 459/2012/EU). Nuclei of metals as well as organics are suspected to significantly contribute especially to the ultrafine particle size fractions, and thus to the particle number concentration. In the project GasOMeP (Gasoline Organic & Metal Particulates) metal-nanoparticles (including sub 20nm) from gasoline cars are investigated for different engine technologies. In the present paper some results of investigations of nanoparticles from four gasoline cars - an older one with MPI and three newer with DI - are represented.