Investigation of exhaust gas dispersion in the near-wake region of a light-duty vehicle

Abstract

The air pollution induced by urban traffic has addressed much attention in recent years as the rapid urbanization and the fast increase of vehicle number in urban area. In this study, we attempted to investigate the dispersion behavior of exhaust gas from exhaust pipe using computational fluid dynamics approach. The time-averaged CO 2 concentration, velocity and temperature profiles along the centerline of the vehicular exhaust plume were simulated in varied situations. The computational results showed good agreement with the experimental data and the numerical model was validated to be an effective method to investigate the pollutant dispersion in the near-wake region of a vehicle. Based on it, the numerical simulations were extended to explore the impacts of the emit concentration, the emit direction and the incoming velocity on the flow dynamics and CO 2 dispersion. The outputs indicated that the emit concentration could change the pollution level in the near-wake region of a vehicle and the emit direction may alter the spreading direction of the vehicular exhaust plume. The incoming velocity was found to have dominant influence on the dispersion of pollutant due to induced vortices and turbulence behind the vehicle. These findings are expected to provide important insight into evaluating the design and control strategies for alleviating mobile source emissions.

Temporal Evolution of Vehicle Exhaust Plumes in a Congested Street Canyon Environment

“…Computational fluid dynamics (CFD) models have been employed to simulate exhaust gas dispersion from vehicle exhaust pipes [39][40][41][42]. Studies [43][44][45][46] have examined the effects of initial emission concentration, exit velocity, exit direction, and crosswind intensity on exhaust plume dispersion, both experimentally and numerically. CFD studies of street canyons have offered valuable insights into wind fields and pollutant transport [47,48],…”

“…The concentration gradients within this heterogeneous environment were found to be steep [29], so it can be hard to estimate pedestrian exposure [28]. Moreover, the majority of studies have focused on experiments in relatively ideal microenvironments, such as wind tunnels [57] and controlled lab-like environments [43][44][45]. There is a scarcity of research addressing real-world kerbside measurements.…”