Spray dedusting scheme under hybrid ventilation at a fully mechanized excavation face.

In order to evaluate the dust suppression performance with a spraying system at the fully mechanized excavation face, an airflow-droplet-dust multiphase coupling model was established based on the Eulerian-Lagrangian method. Subsequently, the model's accuracy was validated experimentally using a self-developed system for measuring dust suppression efficiency. For the pressure/exhaust hybrid ventilation condition, the following conclusions can be drawn: with an increase of airflow migration distance, the number of vortices gradually decreased, and dust-capturing probability caused by collision with wall decreased gradually along the axial direction of the roadway. Jointly driven by the rebounded airflow, the entrainment effect of high-velocity jets around the pressure inlet, and the transverse vortex field near the cutting face, three high-concentration dust particle clusters, denoted as particle flows I, II, and III, were formed, and the distribution patterns of dust particle clusters after the implementation of different spray schemes were determined. By analyzing the droplet field distribution surrounding the coal cutting head and comparing the dust suppression performance, the study proposed two optimal spray schemes: with gravity-driven supply of water, the spray scheme K2.0-4 MPa delivered optimum dust suppression performance, and the mean dust concentrations at specific fixed operating points dropped to 130 mg/m; after utilizing a booster pump, the P2.0-8 MPa spray scheme delivered optimum dust suppression performance, with a mean dust concentration at fixed operating points dropping to 65 mg/m. After applying the K2.0-4 MPa and P2.0-8 MPa schemes, the dust suppression performance was better for the dust with bigger size. The dust suppression efficiencies for the respirable dust were less than 60.7 and 72.5%, respectively. Other dust prevention measures should be taken to further reduce the dust hazard.