Using Artificial Ash to Improve GPF Performance at Zero Mileage
To be published on April 2, 2019 by SAE International in United States
Gasoline particulate filters (GPF) with high filtration efficiency (>80%) at zero mileage are in growing demand to meet increasingly tight vehicle emission standards for particulate matter being implemented in US, EU, China and elsewhere. Current efforts to achieve high filter performance mainly focus on fine-tuning the filter structure, such as the pore size distribution and porosity of the bare substrate, or the washcoat loading and location of catalyzed substrates. However, high filtration efficiency may have a cost in high backpressure that negatively affects engine power. On the other hand, it has been widely recognized that very low amounts of ash deposits (from non-combustible residue in the exhaust) introduced by mileage accumulation during engine break-in can significantly increase filtration efficiency with a mild backpressure increase. This observation led to a potentially alternative approach to increase zero mileage particulate filtration by coating the filter with a small amount of very fine, thermally stable particles with sizes comparable to ash. In the present study, this new approach was investigated by loading a bare filter substrate with submicron alumina particles generated by an atomizer. The backpressure of this ash coated substrate was measured by a cold flow bench test. Particle mass and number emission were measured over FTP and WLTP test cycles using a 2.3L GTDI vehicle. The filter performance before and after coating with artificial ash will be compared and discussed.