Particle Size-Dependent Filtration Efficiency and Pressure Drop of Gasoline Particle Filters with Varying Washcoat Volumes

Gasoline particulate filters (GPFs) are an effective means of reducing particle emissions from gasoline direct injection (GDI) engines. This paper explores the filtration efficiency and pressure drop of three GPFs with varying in-wall washcoat volumes through three parameters: particle size, flow rate of gas through the GPF, and amount of soot accumulation. The three GPFs are tested on a custom filtration efficiency test rig with a miniature inverted soot generator used as a particle source at three space velocities of: 32, 000, 97, 000, and 161, 000 h−1. A scanning mobility particle sizer (SMPS) is used to measure the filtration efficiency and amount of soot accumulated on the GPF. The GPFs are loaded with soot until the average filtration efficiency reached > ~ 98%. Results show that the filtration efficiency is a function of particle size, soot loading, and space velocity. With increasing soot loading on the GPF, the filtration efficiencies increase significantly and become less sensitive to mobility diameter. Filtration efficiency is generally found to decrease with increasing space velocity. For clean filters, the GPF without washcoat has the same or higher filtration efficiency than the GPFs with washcoat. At high amounts of soot accumulation, the GPFs with a washcoat have the highest filtration efficiency. The coated filters have a much higher rate of filtration efficiency and pressure drop increase compared to the bare filter. The mechanisms leading to the observed trends in filtration efficiency and pressure drop are also discussed.