Particle number and size distribution in hybrid electric vehicles using Low-Level Methanol–Gasoline blends

• First study to investigate methanol-blended fuels on particle number emissions from HEVs. • Emission characteristics analyzed across cold-start, hot running, and aggressive driving modes. • Real-time changes in particle size distribution evaluated during engine restart in HEVs. As part of decarbonization strategies in the transportation sector to mitigate global warming, the use of methanol-blended gasoline is gaining attention. Despite extensive research on particle number (PN) emissions in conventional vehicles, studies on their impact in hybrid electric vehicles (HEVs), which are gaining market share, remain limited. This study evaluates the influence of low-concentration methanol-blended fuels (M10 and M20) on particulate emissions in HEVs. Two HEV types, equipped with direct injection (DISI) and port fuel injection (PFI) engines, were tested under FTP-75 (four bags), HFED, and US06 driving modes, and PN 23 and size distributions were measured. Results show that the DISI HEV exhibited an overall decline in PN 23 emissions with increasing methanol content, with decreases in nuclei-mode particles under cold conditions and in accumulation-mode particles under warmed-up conditions. In contrast, the PFI HEV showed an increasing trend in PN 23 emissions with higher methanol content, particularly during cold restarts, driven by a rise in nuclei-mode particle emissions.