Real driving particle number (PN) emissions from China-6 compliant PFI and GDI hybrid electrical vehicles.

Abstract In this paper, the real driving particle number (PN) emissions from two China-6 compliant hybrid electrical vehicles (HEVs) were measured using a certification-level portable emission measurement system (PEMS) and strict adherence to the regulatory procedures for real driving emission (RDE) testing. The results show that the trip-averaged PN emission factors for the port fuel injection (PFI) HEV and the gasoline direct injection (GDI) HEV were 1.15E+12 and 1.71E+12#/km respectively, much higher than the engine-only counterparts and failing the existing RDE limits. Enriched air-fuel mixtures and probably lowered catalyst conversion efficiencies as a result of more frequent engine stop-and-goes of the HEVs are found to be the underlying reasons for the extra PN emissions. The test results also suggest the necessity to amend the power management strategy currently widely used in HEVs to deal with the PN issue. Highlights • Real-word PN emissions of two China-6 HEVs were tested following RDE procedures. • The RDE PN for the PFI and GDI-HEVs were 1.15E+12 and 1.71E+12#/km respectively. • Fuel-rich and low TWC efficiency since frequent engine-starts caused HEVs' more PN. • The power management strategy of HEVs may need amending to cope with high PN. [ABSTRACT FROM AUTHOR]