Airflow Distribution and Methane Concentration At Heading Faces with Auxiliary Ventilation

The airflow velocity vectors and methane concentration at heading faces with auxiliary ventilation are investigated by different methods. The airflow velocity vectors by a forcing and an exhausting auxiliary fan are measured in actual size model galleries. The airflow movement and gas concentration at a heading face; when forcing, exhausting and combined system of ventilation are utilized, are examined by means of the visualization technique by LASER light in a reduced scale model. It is found that the location of forcing and exhausting duct ends have significant effects on airflow and consequently on gas concentration at the heading face. The flow pattern in the reduced scale model shows similar behavior to those observed in actual size galleries. The forcing air velocity at the duct end has almost no significant effect on the airflow pattern at the heading face. The optimal airflow quantities and duct locations to reduce the hazard of methane accumulation are investigated with special attention to the combination of forcing and exhaust system of ventilation. The airflow is also examined when a large size machine such as a road-heading machine is placed in the heading face.