Characteristics of on-road particle number (PN) emissions from a GDI vehicle depending on a catalytic stripper (CS) and a metal-foam gasoline particulate filter (GPF)

Particle number (PN) emissions must be below 9.0 × 10¹¹ #/km according to the Euro 6d regulation with a conformity factor (CF) of 1.5 during a real driving emissions (RDE) test, including the cold start phase. Thus, the object of this study is to analyze the on-road PN emissions characteristics under a cold start condition of a gasoline direct injection (GDI) vehicle depending on a catalytic stripper (CS), a gasoline particulate filter (GPF), the cold start phase, and the trip section using a corona charger type particle sensor, a CS, and an exhaust flow meter. Because the fuel-rich mode and retarded injection timing were applied to compensate for engine instability and caused incomplete combustion and deterioration of fuel vaporization during the cold start phase, PN emissions during the cold start phase accounted for a significant portion of the total PN. On-road PN emissions for the total trip were 2.71 × 10¹² (without CS and GPF), 1.72 × 10¹² (with CS and without GPF), 1.47 × 10¹² (without CS and with GPF) and 9.50 × 10¹¹ (with CS and GPF) #/km for cases A, B, C and D, respectively. The average CS effects on the decrease of PN emissions were 35.4% and 32.2% in the urban, 52.2% and 63.4% in the rural, 22.8% and 88.6% in the motorway, and 36.5% and 35.6% in the total trip sections without and with GPF, respectively. The average GPF effects on the reduction of PN emissions were 42.7% and 39.9% in the urban, 58.2% and 68.0% in the rural, 27.9% and 89.3% in the motorway, and 45.6% and 44.8% in the total trip sections without and with CS, respectively.