Fundamental Study of GPF Performance on Soot and Ash Accumulation Over Artemis Urban and Motorway Cycles - Comparison of Engine Bench Results with GPF Durability Study on Road

Paper #:
  • 2017-24-0127

  • 2017-09-04
With the increasing number of engines utilizing direct fuel injection and the upcoming more stringent emission legislation, regulating not only particulate mass (PM) but particulate number (PN), emissions of Direct Injection Spark Ignition Engines (DISI) are becoming of increasing concern. Gasoline Particle Filters (GPF) represent a novel potential measure to reduce particle number emissions from DISI engines and are particularly effective in view of the tight particle number limits requirements at cold start and over RDE. Even if some learning from the development and application of particulate filters to diesel engines can be transferred to gasoline engines, the particulate consistence, the mass to number ratio and the temperature as well as the gas composition of gasoline engines are significant different to diesel engines. Therefore, there is the need to study the application of particulate filters to gasoline engines carefully. In addition to the filtration efficiency and backpressure behaviour of GPF, of great concern is the understanding of the ash accumulation mechanism and its negative impact on the backpressure over lifetime. This paper presents the results of the fundamental study of an uncoated ceramic GPF in the exhaust of a 1,6 liter turbo DISI. Data soot and ash accumulation applying two extreme drive cycle conditions (Artemis urban vs. Artemis Motorway) are reported. The drive cycles have been simulated on a dynamic engine bench and each cycle has been operated over 20tkm; PN emissions are measured over WLTC and NEDC cycle after 20tkm. The results are discussed with respect to the differences of each cycle on the ash formation and backpressure increase, but also with respect to the possibility to extrapolate the results to a more balanced driving pattern over 160tkm. Results from the engine-bench investigation are compared to a vehicle durability run, using the same engine and type of GPF in the under-floor (UF) location. Results show very good PN filtration efficiency of the GPF, above 70% fresh and above 90% with increasing mileage, low soot accumulation, low ash amount; ash is mainly related to the oil consumption of the engine and small differences were observed between the two Artemis cycles: however, the urban cycle showed higher ash amount over 20tkm (1,26 g/l) compared to the Artemis Motorway (0,4 g/l). These ash values from the engine bench well correlate with the findings of the vehicle durability run. Post mortem analysis of the GPF after engine bench and vehicle durability tests are also reported.
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