Assessment of gaseous, particulate, and unregulated emissions from diesel compression ignition and LPG direct injection spark ignition minibus vehicles under the world harmonized vehicle cycle on a chassis dynamometer

Construction of harmful emission inventory from conventional and sustainable low carbon fueled vehicles is important issues to improve urban air quality and human health. In this study, the gaseous, nanoparticle, and unregulated gaseous emission formation behavior from a medium-duty minibus were investigated using the World Harmonized Vehicle Cycle (WHVC). The state-of-the-art diesel and turbocharged direct-injection liquefied petroleum gas (LPG) vehicle were tested on a chassis dynamometer. The after-treatment system of the 3.9-L diesel engine was composed of the DOC, DPF and SCR, which satisfy the Euro 6 emission regulation. The 3.3-L stoichiometric spark ignition direct injection LPG engine was a TWC-only system. The formation of harmful emission components from the light-duty minibus operation was closely related to powertrain types, combustion mechanisms, after-treatment devices, and physicochemical properties of the tested fuels. Additionally, the chemical composition and low heating value (or energy content) of the respective fuels substantially affected the vehicle CO₂ emissions and fuel economy performance. Compared to LPG vehicle, the THC and NOx emissions from diesel vehicle were 63% and 511%. Similar PN concentrations were measured with each powertrain, but 2–3 times higher nucleation mode particles were released with diesel vehicle. Two vehicles showed comparable CO₂ emissions, while fuel economy from diesel and LPG vehicle were 6.81 km/L and 4.60 km/L. The proportions of N₂O and CH₄ emissions with ozone forming potential (OFP) were 1.2% (diesel) and 0.3% (LPG), which showed the potential to mitigate the CO₂-equivalent emissions from LPG minibus.