The use of induction fans for face ventilation in room and pillar mines has proved to be an
efficient, flexible, and viable technique. In addition to their merits over conventional
systems, induction fans enable remote controlled mine operations with low maintenance
requirements. Theoretical investigations were conducted initially to verify the potential of
free air jets in mine ventilation.
A laboratory model using water as the fluid medium was designed to study the flow
characteristics of a jet fan in a blind entry. The model was tested in a variety of brattice
curtain and nozzle combinations to investigate the ventilating efficiency of jet fans. A jet
fan was selected and tested in a full scale model and in a coal mine. Experiments were
conducted to evaluate the laboratory flow models. Flow quantities and velocities in the
entry were measured using state-of-the-art instrumentation to quantify various parameters.
Air velocities near the face were found to be satisfactory to dilute contaminants from the
face. A model for the axial velocity profile of the jet was suggested. Beyond 25m distance
from the jet fan exit the jet tended to move away from the wall to the opposite wall.
Carbon dioxide was used as a tracer gas to measure the effective ventilating air quantity
near the face and re-circulation in various tests. The re-circulation involved in the system
was found to be less than 40% in all the experiments. It was also found that the use of line
curtains in combination with a jet a fan can eliminate any type of re-circulation.
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