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Wall-mounted swirling ventilation is a new type of system in mechanized excavation faces with a dust suppression performance that is closely related to the blowing-to-suction flow ratio. Physical and simulation models were developed according to the No. C103 mechanized excavation face in the Nahe Coal Mine of the Baise Mining Bureau, Guangxi Province to optimize the blowing-to-suction flow ratio for wall-mounted swirling ventilation. Both the k-ε turbulence model and the discrete phase model were utilized to simulate airflow field structures and dust concentration distribution patterns at various blowing-to-suction flow ratios. The results suggest that higher blowing-to-suction flow ratios increase the airflow field disturbance around the working face and weaken the intensity of the axial air curtain. On the other hand, both the intensity of the radial air curtain and the dust suppression effect are enhanced. At a blowing-to-suction flow ratio of 0.8, the wall-mounted swirling ventilation system achieved the most favorable dust suppression performance. Both the total dust and respirable dust had their lowest concentrations with maximum efficiencies of reducing both types at 90.33% and 87.16%, respectively.

Spraying for dust suppression is a conventional technological means for industrial dust control. The traditional spraying technique shows a few shortcomings, including low dust suppression efficiency, great water consumption, and failure in far-distance dust suppression. This study proposed a novel combined spraying dust suppression device and established the related physical model and mathematical model. Using the CFD numerical simulation method, the basic characteristics of the airflow field and spray field around the device and the related influencing factors were investigated in depth. Results showed that the Coanda effect appeared near the wall surface in the air duct when the combined spraying dust suppression device was operated. Under this effect, negative pressure formed at the center of the device. The velocity of the combined device showed a symmetrical distribution and decayed steadily downward from the outlet of the device. An obvious stratification can be observed in the spray field. The mean droplet size first increased and then decreased along the airflow direction. Meanwhile, the effects of the air supply pressure and water supply pressure were examined. On the one hand, the velocity of the combined spraying dust suppression device and the spraying range were in direct proportion with the air supply pressure. As the air supply pressure increased, the droplet size first increased and then decreased. On the other hand, increasing the water supply pressure imposed almost no effect on the airflow field of the combined spraying dust suppression device but can reduce the droplet size and enhance the spraying range.