By Vasu Gangrade, mining engineer, NIOSH; Samuel Harteis, lead mining engineer, NIOSH; and J.D. Addis, research scientist, NIOSH
Researchers with the National Institute for Occupational Safety and Health, Pittsburgh Mining Research Division, constructed a 1:30 scale physical model of a portion of a longwall operation to simulate the airflow characteristics along the face and along or through the gob. The Longwall Instrumented Aerodynamic Model (LIAM) is built with critical details of the face and face machinery, such as shearer, shields, conveyor belt etc., as well as a portion of the gob and the barrier pillars. LIAM is instrumented with pressure gauges, flow anemometers, temperature probes, a variable speed fan, and a data acquisition system to enable investigation of face, entry and gob flows for variable mining configurations. LIAM offers the flexibility of carrying out tests for variable mining configurations such as bleeder/bleederless and exhausting/blowing ventilation systems to supplement numerical modeling studies and mine site studies where field measurements may be limited. The LIAM design is described in detail and results are presented from a study of gob-face exchanges, distribution of air at the critical face-tailgate air split, and airflow patterns in the gob for different caving characteristics. Scaling relationships were derived on the basis of Reynolds and Richardson’s number to preserve the physical and dynamic similitude by optimally scaling turbulent dispersion, pressure gradients, flow velocity, permeability, face dimensions, transit times, and ventilation airflow. These results are compared to field data and previous numerical modeling studies.
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