Experimental study on the effect of loading and regeneration for an optimized management of the DPF

Limits imposed by worldwide emission regulations on particulate emission from diesel engine exhaust resulted in the employment of filters to cut down pollutants to acceptable values after they are produced into the cylinders. The management of the entire system engine + aftertreatment demonstrated to play a fundamental role in order to ensure compliance with the increasingly stringent emission limits. This paper is devoted to investigate in detail the role of the engine operative conditions on the filter behavior during the loading phase and to analyze how the regeneration strategy affects the filter efficiency and its pressure drop during the subsequent loading phase. These aspects retain a relevant role in the light of the new limits for particle emission from the tailpipe related not only to the number of particles but also to the cut point for PN measurement, which will be lowered from the current 23 nm-10 nm (PN10). Testing was performed on a Euro6 engine; the results highlight that the specific engine operation deeply af-fects the filter loading process, with differences in the pressure drop trend (both in the shape and in the values) and in the DPF efficiency. The filter efficiency, once the regeneration event is completed, depends on the regeneration strategy: when the clean filter condition is restored, a slow increase of filtration efficiency is observed; when the regeneration event does not restore the clean filter status, the subsequent loading process is characterized by better filtration properties. The obtained findings represent additional useful information to account for in the procedure devoted to define the optimal strategy to manage the engine: the regeneration events should be planned not only by considering the pressure drop across the filter but accounting also for the filtration performance once the regeneration is completed, thus to define the optimal strategy to manage the engine + aftertreatment able to comply with the new stringent limits on tailpipe particles and to reduce fuel consumption and oil dilution.