An experimental study of particulate matter and volatile organic compounds (VOCs) emissions was conducted on a direct injection gasoline (DIG) engine and a port fuel injection (PFI) engine which both were produced by Chinese original equipment manufacturers (OEMs) to investigate the impact of fuel properties from Chinese market on particulate and VOCs emissions from modern gasoline vehicles. The study in this paper is just the first step of the work which is to investigate the impact of gasoline fuel properties and light duty vehicle technologies on the primary and secondary emissions, which are the sources of particulate matter 2.5 (PM2.5) in the atmosphere in China. It is expected through the whole work to provide some suggestions and guidelines on how to improve air quality and mediate severe haze pollution in China through fuel quality control and vehicle technology advances.
In this paper, two testing fuels with different aromatics were blended to investigate the influences of high aromatics gasoline fuels in the current Chinese market on vehicle emissions. A DIG and a PFI engine were selected for emission testing with the measurements of primary particulate emissions as well as regulated gaseous emissions and VOCs emissions. For primary particulate emissions, particle mass (PM), particle number (PN), size distribution and compositions are all included in the measurement. The test results demonstrated that fuel compositions have significant impact on particulate and VOCs emissions for both DIG and PFI engine. Higher aromatics content in gasoline from the current China market resulted in much higher PM and PN of DIG as well as much higher VOCs emissions of PFI.
Comparing the testing results of PFI and DIG engine, it was showed that the particulate compounds of DIG engine mainly consisted elemental carbon (EC), organic matter (OM) and small amount of inorganic ions. In contrast, particulates emitted from PFI engine mainly consisted OM and small amount of EC and inorganic ions.
The VOCs emissions were mainly composed of alkanes (39%-51%), alkenes (22-31%), aromatics (18%-27%), oxygenated VOCs (≈3%) and alkynes (≈1%) compounds. The VOCs emissions of PFI engine showed up to 100 times higher than that of DIG engine under the same engine operating conditions. Similar to the particulate emissions, higher aromatics content in gasoline tend to increase the aromatics content in VOCs emissions of PFI engine.
As both particulate and VOCs are the main contributors to PM2.5 formation, a suggestion was made based on the results that the investigation of fuel properties’ and vehicles’ influences on PM2.5 in China should focus on not only the impact of fuel properties on the primary particulate emissions of DIG but also that on the VOCs emissions and secondary particulate formation of PFI engine.