Evaluation of Low Mileage GPF Filtration and Regeneration as Influenced by Soot Morphology, Reactivity, and GPF Loading 2019-01-0975

As European and Chinese tailpipe emission regulations for gasoline light-duty vehicles impose particulate number limits, automotive manufacturers have begun equipping some vehicles with a gasoline particulate filter (GPF). Increased understanding of how soot morphology, reactivity, and GPF loading affect GPF filtration and regeneration characteristics is necessary for advancing GPF performance. This study investigates the impacts of morphology, reactivity, and filter soot loading on GPF filtration and regeneration. Soot morphology and reactivity are varied through changes in fuel injection parameters, known to affect soot formation conditions. Changes in morphology and reactivity are confirmed through analysis using a transmission electron microscope (TEM) and a thermogravimetric analyzer (TGA) respectively.

Evaluations regarding the impact of these varied soots on GPF performance is accomplished through monitoring of GPF filtration efficiency as a function of soot loading and monitoring of soot oxidation rates during GPF regeneration events. Size-dependent filtration efficiency across the GPF is determined with a Scanning Mobility Particle Sizer (SMPS). Soot oxidation during regeneration events is determined using a radio frequency (RF) sensor and periodic weighing of the GPF on a high-resolution scale.

Findings from this work show that soot reactivity and morphology are dependent on fuel injection conditions. Additionally, this work suggests GPF filtration is dependent on particle morphology, with higher filtration efficiency observed for particles formed at the late start of injection condition. These particles were noted to have more dendritic structures and smaller primary particle sizes. These particles may be more likely to catch onto nearby pores within the filter substrate as they follow the tortuous air flow path through the porous filter walls.

Finally, this work indicates good correlations can be made between TGA isothermal tests and GPF regeneration events across large variations in soot reactivity.