The use of Diesel engines has strongly increased during the last years and now represents 30% of the sales in Europe and up to 50% of the number of cars in circulation for some countries. This success is linked not only to the economical aspect of the use of such vehicles, but also to the recent technological improvements of these engines. The new technical solutions (high pressure direct injection, turbocharging…) have indeed allowed the increase of these engine performances while decreasing their fuel consumption, pollutant emissions and noise level.
From an environmental point of view, Diesel engines are nevertheless penalized by their particulate and NOx emissions. The study and the treatment of the particulate, highly criticized for their potential impact on health, are the subject of numerous works of characterization and developments.
PSA Peugeot-Citroën has recently launched its particulate filter technology on several types of vehicles. In order to evaluate the durability of this technology over a long period of time, a study program has been set-up by ADEME (French environmental agency), IFP Powertrain, PSA Peugeot-Citroën and G7 (a Parisian taxi company). The objective is to study the evolution of several taxis and their after-treatment system performances over 80 000 km mileage in hard urban driving conditions, which corresponds to the recommended mileage before the first DPF maintenance.
More specifically, the following evaluations are being performed at regular intervals (around 20 000 km):
Regulated gaseous pollutant emissions on NEDC cycle (New European Driving Cycle)
Particulate emissions, by mass measurement on NEDC but also by particle number and size measurement with SMPS (Scanning Mobility Particle Sizer) technique on NEDC and on unconventional steady-state running points.
Unregulated pollutant emissions (hydrocarbons speciation C1-C13, oxygenated compounds)
The results obtained until now have not shown any degradation of the particulate filter efficiency. This paper presents the methodology setup and the explanation of the first results obtained. Indeed, a more specific study has shown that most of the aerosols measured with SMPS are composed of liquid fractions, mainly sulfates due to sulfur coming from the fuel, but also from the lubricant. The impact of sulfates stored on the catalyst surface during low temperature running phases and removed during high temperature running phases has also been outlined.