Nanoparticle filtration characteristics of advanced metal foam media for a spark ignition direct injection engine in steady engine operating conditions and vehicle test modes

In this study, the particle formation and reduction characteristics at the engine-out position, after a three-way catalyst (TWC) and a metal foam gasoline particulate filter (GPF), were evaluated for a gasoline direct-injection (GDI) engine under part-load operating conditions. The vehicle tests were performed under the Federal Test Procedure-75 (FTP-75) and the Highway Fuel Economy Test (HWFET) modes. Particle number (PN) concentrations, size distributions, and the filtering efficiency with the GPF were evaluated with a condensation particle counter (CPC) and a differential mobility spectrometer (DMS500). Under steady engine operating conditions, the PN concentrations at the engine-out position were 9.7 × 10⁵-2.5 × 10⁶ N/cc. While, the PN concentrations after the GPF were 9.2 × 10⁴-3.5 × 10⁵ N/cc, and the PN was reduced by 77%-96%. The PN filtering efficiency with the GPF-GDI vehicle reached approximately 58% in the FTP-75 and 62% in the HWFET mode. The PN concentration of the GPF-GDI vehicle was significantly reduced to 3.95 × 10¹¹ N/km for the FTP-75 and 8.86 × 10¹⁰ N/km for the HWFET mode. The amount of nucleation mode particles below 23 nm was substantially reduced with the GPF-GDI vehicle. The fuel economy, CO₂, and regulated emissions of the GPF-GDI vehicle were equivalent to those of the base GDI vehicle under the vehicle certification modes.