Long-duct forced and short-duct exhaust ventilation system in tunnels: Formation and dust control analysis of pressure ventilation air curtain

To decrease the high concentration dust in tunnels with a long-duct forced and short-duct exhaust ventilation system, airflow and dust field migration behaviours, when different distances between pressure ventilation outlet and tunnel face are involved, are analysed with the application of numerical simulation and field measurements in this study. The formation principle of air curtain and the dust control rule in tunnels with a long-duct forced and short-duct exhaust ventilation system are also elaborated and the conclusions can provide the guidance for dust control in tunnels. Numerical simulation shows that the formation of pressure ventilation air curtain is mainly determined by the distance between the pressure ventilation outlet in eddy airflow field and tunnel face. The mathematical relationship of the diffusion distance of high concentration dust is determined as a function of the distance between the pressure ventilation outlet and tunnel face. Field measurements are carried out in the second auxiliary tunnel of Longgu to determine the dust concentration along the tunnel. The results show that when the distance between the pressure ventilation outlet and tunnel face is 35 m, the dust concentration is lowered to less than 18.2 mg/m(3), demonstrating the effective dust control of the pressure ventilation air curtain. It also ensures the safety of tunnel production and the protection of the workers' physical health, and reduces the occurrence of pneumoconiosis. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.