Dispersion behaviors of exhaust gases and nanoparticle of a passenger vehicle under simulated traffic light driving pattern

• Published in: The Science of the total environment 2020-10, Vol.740, p.140090-140090, Article 140090
• Main Authors: Deng, Banglin, Chen, Yangyang, Duan, Xiongbo, Li, Di, Li, Qing, Tao, Da, Ran, Jiaqi, Hou, Kaihong
• Format: Article
• Language: English
• Subjects: CFD; environment; human health; Nanoparticle; pipes; Pollutant dispersion; pollutants; Traffic light; turbulent flow; ventilation systems; wind speed
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.140090

In the present study, the flow structure and pollutants dispersions were investigated by experiment and simulation on a typical passenger vehicle under simulated traffic light driving pattern. Some important findings were achieved: 1) gaseous pollutants diffuse drastically during first 0.3–0.6 m distance depending on wind velocity, at 1.25 m/s wind speed which is the similar level of exhaust gas, the pollutant concentration rises suddenly at ~0.6 m because exhaust plume is twisted by bottom gas flow, and a low velocity zone is produced; 2) as wind speed increases, the vehicle-induced turbulence is more and more important on pollutant dispersion pattern than exhaust plume dynamics. For instance, at 1.25 m/s and 4.17 m/s wind speeds, pollutants decrease to zero at ~1.6 m behind tail pipe, but at 0 m/s condition, pollutant relative fraction is still at ~0.12 level even at very long distance; 3) solid particle has larger attenuation rate than gaseous pollutants, only after ~0.6 m the particle number (PN) and diameter are very close to background values. Solid particle can diffuse to farther distance in vehicle transverse direction, when a car passes through the pedestrians with a 3 m distance, pedestrians expose to 2.6–3 times higher PN relative to atmosphere with diameters of 28–33 nm, this is very hazardous for human health; 4) exhaust pollutants disperse difficultly when followed by a car with a commonly waiting distance. At free dispersion scenario only behind ~0.6 m, PN decreases to 5800 #/cm3 (background value), but in-cabin PN of the following car (behind 0.8 m) rises to 3.5 × 104 #/cm3 (even after 2–3 times decay through ventilation system). This study provides implications for future studies on transport planning. [Display omitted] •Gaseous pollutants diffuse drastically during first 0.3–0.6 m distance depending on wind velocity.•With wind speed increasing, pollutant dispersion is more and more determined by vehicle-induced turbulence.•Particles degrade into background at ~0.6 m while gaseous pollutants at least keep at 0.12 fraction till far.•When a vehicle passes with 3 m, pedestrians expose to 2.6–3 times higher PN than atmosphere value with diameters of 28–33 nm.•Exhaust pollutants disperse difficultly when followed by a car with a commonly waiting distance (0.8 m).