Research on SPN10 and SPN23 emission characteristics of HEVs: Effect of gasoline particulate filter (GPF) on range-extended electric vehicle (REEV).

Driven by ever-tightening fuel consumption and exhaust emission regulations worldwide, research on the ultrafine particle characteristics of hybrid vehicles becomes necessary. This study tested a REEV and a plug-in hybrid electric vehicle (PHEV) over the Worldwide Harmonized Light Vehicles Test Cycle (WLTC) and compared their SPN23 and SPN10 emissions. In addition, the influences of GPF installation and catalyst temperature on the particulate emissions from the REEV were also analyzed. It is found that the particle emissions from both vehicles increased, particularly SPN10, during each engine start and under high‑load operation. More than 95% of exhaust-borne particles were formed during engine cold-start and warm-up stages, though this short period only accounted for 13% of the cycle time. On a cycle-average, SPN10 emissions were 32.2% and 48.1% higher than SPN23 of the PHEV and REEV. Engine-out SPN10 emissions under high loads ascended more sharply for the REEV, inferring a unique risk related to this hybrid architecture. Highly transient engine speeds, which may be attributed to fuel-efficient engine control strategy, could also cause deteriorated particle emissions during low- to mid-speed stages. After the installation of GPF, the SPN removal efficiency increased from less than 50-76.5% and 86.6% for SPN23 and SPN10. The removal efficiency for SPN10 under mid- and extra-high-speed stages surged more pronouncedly.