EVALUATION OF UNAGED GPF FILTRATION AND REGENERATION AS INFLUENCED BY SOOT MORPHOLOGY, REACTIVITY AND GPF LOADING 2019-01-0975
As European tailpipe emission regulations for gasoline light-duty vehicles require reductions in particulate number, automotive manufacturers have begun equipping some vehicles with a gasoline particulate filter (GPF). Increased understanding of how soot morphology, reactivity and GPF loading interact and affect GPF filtration and regeneration characteristics is necessary for advancing GPF filtration performance. This study leverages changes in fuel injection parameters (likely to affect soot formation) to generate soot with variations in morphology and reactivity. Furthermore, this work sets out to explore the impact morphology, reactivity, and filter soot loading have on GPF filtration and regeneration.
Soot morphology is explored using a transmission electron microscope (TEM), and soot reactivity is evaluated using a thermogravimetric analyzer (TGA) and isothermal oxidation events. Given the concern that discrepancies may exist between real world soot oxidation on a gasoline particulate filter and laboratory TGA systems, soot reactivity is also evaluated using select conditions during a temperature-controlled regeneration event with the engine and an uncoated GPF. Loss of soot mass in the GPF during the regeneration event is evaluated using a radio frequency (RF) sensor.
GPF filtration efficiency is evaluated as a function of soot loading for two of the reviewed operating conditions, late start of injection and low injection pressure, as these conditions exhibited strong differences in soot morphology. The level of soot loading on the filter is determined with an RF sensor and further validated through periodic weighing of the gasoline particulate filter on a high-resolution scale. Size-dependent filtration efficiency across the GPF is determined with a Scanning Mobility Particle Sizer (SMPS).
Findings from this work suggest that soot reactivity and morphology are dependent on the engine operating condition. Additionally, this work suggests GPF filtration is dependent on particle morphology, and therefore engine operating condition, and reactivity differences observed with a TGA may be correlated to real world oxidation of soot on a GPF.
Jordan Elizabeth Easter, Angela Fiano, Stanislav Bohac, Kiran Premchand, John Hoard
FCA US LLC, University of Windsor, University of Michigan