Size-resolved engine exhaust aerosol characteristics in a metal foam particulate filter for GDI light-duty vehicle

The particulate emissions generated from a side-mounted 2.4 L gasoline direct injection (GDI) engine were evaluated using a metal foam-type gasoline particulate filter (GPF), placed on the downstream of a three-way catalyst. An ULEV legislation-compliant light-duty vehicle was tested under the new European driving cycle (NEDC) and at constant-speed driving conditions. Particle number (PN) concentrations, particulate size distribution and the filtration efficiency of the GPF were evaluated with the condensation particle counter (CPC) and the differential mobility spectrometer (DMS). The PN emissions for the entire NEDC were 1.17E+12 N/km for the base GDI vehicle and 4.99E+11 N/km for the GPF-equipped GDI vehicle, and the filtration efficiency of the GPF was 57%. In particular, the number of sub-23 nm particles formed in the GDI vehicle was substantially reduced, with 97% efficiency. The pressure drop in the metal foam-type GPF was constrained to be below 1.0 kPa at a 120 km/h vehicle speed, and as a result, the fuel economy and the CO2 emission for the GPF-applied vehicle were equivalent to those for the base vehicle.