Influences of ventilation velocity on dust dispersion in coal roadways
Abstract The ventilations of pressure cylinders is a widely used practice in coal mine roadways in China. It has been determined that the velocities of the ventilations will directly affect the diffusion of the dust particles which reduce the visibility of road-header drivers, and also tend to slowdown operating efficiency. In this study, a CFD-DPM method was adopted in order to examine the airflow flow and dust pollution behaviors in coal mine roadways under various ventilation velocities. The results showed that airflow fields could be divided into disordered regions of airflow flow fast and chaos; recirculation regions, where there were dust backflow; and stable regions, from the heading faces to the exits of the coal mine roadways. The airflow were observed to carry the dust particles along the roadway wall away from the pressure cylinders from the disordered regions into the recirculation regions due to the blocks caused by the road-headers. It was observed that the dust migration had slowed down in the areas behind the road-headers due to the sudden decreases in the airflow velocities. Then, major amounts of dust particles were carried by airflow into the stable regions. The remaining dust was carried to the exits of the pressure cylinders as a result of the dust backflow. As a result, areas of approximately 5 m behind of the road-headers, as well as the areas near the exits of the pressure cylinders, contained high dust concentrations. The dust concentrations near the exits of the pressure cylinders into which the dust particles had been attracted due to the strong entrainment effects, were found to increase with increasing of the ventilation velocities. However, this had only occurred when ventilation velocities had exceeded 17 m/s.