Emission Characteristics of Particle Number from Conventional Gasoline and Hybrid Vehicles

Abstract

Vehicular particle number (PN) emissions have garnered increasing attention. In this study, nine light-duty vehicles, involving conventional internal combustion engine gasoline vehicles (ICEVs) and hybrid electric vehicles (HEVs), underwent testing on a chassis dynamometer to elucidate key factors influencing PN emissions. We found that with more stringent emission standards Gasoline Direct Injection (GDI) vehicles exhibited a reduction in PN emission factors. Higher PN emissions for GDI vehicles than vehicles with Multi-Port Fuel Injection (PFI) engines were observed; meanwhile, HEV showed lower PN emissions than ICEVs. PN emissions for cold start consistently exceeded warm start across vehicles with different standards and technologies. Notably, China VI HEV exhibited a substantial 19.2-fold increase in PN emissions for cold start compared to warm start. Analysis on a second-by-second basis revealed that cold-start emissions concentrated in low speed, while warm-start emissions were prominent in extra-high speed. Concerning vehicle specific power (VSP), the lowest mean PN emission rate occurred during idle conditions. PN emissions for China IV-VI ICEVs with GDI engines would increase with the increasing VSP, whereas China VI ICEVs with PFI engines and HEV with GDI engines showed varied patterns of PN emissions, especially under cold start. Our study would further facilitate formulating effective strategies for vehicular PN emissions.