Custer, N., Kamp, C., Sappok, A., Pakko, J. et al., "Lubricant-Derived Ash Impact on Gasoline Particulate Filter Performance," SAE Int. J. Engines 9(3):1604-1614, 2016, doi:10.4271/2016-01-0942.
The increasing use of gasoline direct injection (GDI) engines coupled with the implementation of new particulate matter (PM) and particle number (PN) emissions regulations requires new emissions control strategies. Gasoline particulate filters (GPFs) present one approach to reduce particle emissions. Although primarily composed of combustible material which may be removed through oxidation, particle also contains incombustible components or ash. Over the service life of the filter the accumulation of ash causes an increase in exhaust backpressure, and limits the useful life of the GPF. This study utilized an accelerated aging system to generate elevated ash levels by injecting lubricant oil with the gasoline fuel into a burner system. GPFs were aged to a series of levels representing filter life up to 150,000 miles (240,000 km). The impact of ash on the filter pressure drop and on its sensitivity to soot accumulation was investigated at specific ash levels. Ash deposits and interactions with the filter substrate were studied using x-ray micro computed tomography (CT), focused ion beam milling (FIB), cross section ion milling (CSIM), scanning electron microscope imaging (SEM), and energy dispersive x-rays (EDX). This extensive post-mortem dataset was used to quantify the extent of the substrate-ash interactions. The results highlight the importance of understanding ash impacts on the backpressure and soot loading of GPFs over their full useful life.