In November 2015, the PM and PM particulate matter (PM) levels in platforms, station halls, and rail areas of the Shangcheng and Jiashan Road Station were monitored to investigate air pollution in the Shanghai subway system. The results revealed that in subway stations, PM and PM concentrations were significantly higher than those in outdoor environments. In addition, particle concentrations in the platforms exceeded maximum levels that domestic safety standards allowed. Particularly on clear days, PM and PM concentrations in platforms were significantly higher than maximum standards levels. Owing to the piston effect, consistent time-varying trends were exhibited by PM concentrations in platforms, station halls, and rail areas. Platform particle concentrations were higher than the amount in station halls, and they were higher on clear days than on rainy days. The time-varying trends of PM and PM concentrations in platforms and station halls were similar to each other. Activities within the station led to most of the inhalable particles within the station area. The mass concentration ratios of PM and PM in platforms were within 0.65-0.93, and fine particles were the dominant components.
Many epidemiological studies have shown that long-term exposure to high PM2.5 concentrations can significantly increase the morbidity and mortality of different diseases. Air cleaners are effective in removing PM2.5. In the present research, different filter units were tested to determine their PM2.5 filtration efficiency. The filter face velocity was adjusted to 50%, 75%, 100%, 125%, and 150% of the corresponding rated airflow. The single-pass efficiencies, resistances, and
The effects of the initial preheating perturbation on the dynamical behaviors of FGC wave propagation instability for low-velocity FGC in packed bed are studied numerically. The behaviors of the flame front inclination, break, and shrinking instabilities are always observed in experiments. Based on the experimental phenomena, an initial thermal perturbation model is numerically proposed as to predict the deformation behaviors of the flame front instabilities. The typical flame shapes are obtained depending on filtration velocity, equivalence ratio, and initial preheating temperature difference. It is demonstrated that the development of flame front inclination instability is proportional to the magnitude of initial preheating perturbation. At a lower equivalence ratio, the initial thermal perturbation of 300 K leads to the evolution of flame front break. Increasing filtration velocity leads to the appearance of flame front break, due to the intensification of the hydrodynamic instability. In addition, a perculiar instability of flame front shifting is also confirmed with the initial thermal perturbation of 400 K, which results in a fuel leakage of incomplete combustion.
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