Factors influencing the dust-blocking effect of air curtains during the fully mechanized excavation of working faces

Prevalent research on dust pollution during fully mechanized excavation has mainly focused on the impact of individual factors on the effectiveness of air curtains in fully mechanized excavation sites. However, scant research has been devoted to the interaction between factors, because of which pressure-induced air diversion technology has not been adequately applied to this context.To investigate the impact of the radial distance of the outlet of air, the ratio of this outlet, and the distance between the outlet and the wall-coated air duct on the effectiveness of dust blocking by air curtains, the authors of this study consider the excavation of the working face of the 810 west wing machine tunnel at the Pansan Mine . We used Fluent software to numerically simulate the distribution of wind flow and the diffusion of dust under a distance of the radial outlet of air of 10-25 m, a ratio of the outlet of 0.6-0.9, and an axial distance of the outlet of 6-12 m.The results showed that: ① As the distance of the radial outlet of air increased, the radial vortex air curtain transforms more fully in the tunnel . The wind flow at the front end of the excavation operator was more evenly distributed, and the wind speed was directed toward the working face such that this was more conducive to the formation of an axial dust-blocking air curtain.When the radial distance of the outlet of air was 10 m, vortical characteristics became apparent within a distance of 7 m from the working surface, and the direction of wind became disordered. When the radial distance of the air outlet was 25 m, the wind flow tended to be uniform within 7 m of the working surface, and its direction was evenly distributed toward the working surface. This led to the formation of an axial dust-blocking wind curtain that could cover the entire section.② As the ratio of the radial outlet of air increased, the volume of axial airflow of the rectifier air cylinder decreased to reduce the velocity of axial airflow and the intensity of the jet. This in turn reduced the disturbance caused by the axial airflow to that at the top of the mechanized working face that was being excavated. A higher ratio of the radial outlet of air was more conducive to the formation of an axial dust-blocking flow field, with the wind directed toward the working surface and covering the entire section. This led to an axial dust-blocking air curtain. ③ The dust-blocking ability of the radial vortical air curtain initially increased and then decreased as the ratio of the radial outlet of air increased. Its ability then continued to improve as the ratio was further increased. ④ We implemented the dust-control technology based on the air curtain with forced ventilation-induced diversion. When the pressure-induced volume of air was 300 m³/min and the volume of air suction was 400 m³/min, the distance between the radial outlet of air and the attached wall of the air duct was 20 m. The ratio of the radial outlet of air, and the distance between this outlet and the air duct of the rectifier was 8-10 m. The air curtain was able to collect dust near the port of the dust suction for efficient dust control and removal.We conducted an on-site test of the fully mechanized excavation working face of the 810 west wing machine tunnel. The empirically measured data of wind speed and dust mass concentration at measuring points and the results of numerical simulations were consistent with each other. Highly concentrated dust was blocked at the front end of the working face, and its isolation was noticeable. This confirms the effectiveness of the numerical simulations.