| Description |
U.S. federal regulations pertinent to surface fan installation are concerned with mine safety and give little attention to the aerodynamic design of the installation. As a result, pressure drops has been reported at the installation. Ventilation surveys have shown that these pressure drops could be as high as 40% of fan pressure. The purpose of this study is to identify the sources for such a pressure drop and to reduce it. In recent years, computational fluid dynamics (CFD) software has been successfully used in visualizing the fluid flow for different flow paths (geometries) subject to obstructions. CFD modeling is based on fluid flow principals. They are also applicable to mine ventilation. ANSYS FLUENT, a CFD software, was used as a research tool in this study. A blower and an exhaust system were studied. For the former, using real mine data, the major sources of pressure loss were identified and parametric studies undertaken to minimize those losses. The losses are due to poor installation design with abrupt changes in air velocity and flow direction. Parametric analysis proved that the distance of the fan from any major obstruction is important. Installing the fan at a distance of at least twice the inlet duct diameter reduces the flow separation and formation of eddies. For the exhaust system, it was found that the geometry of the evasée plays an important role in reducing the pressure losses; for instance, a conical evasée recovers the static pressure of the fan better than a rectangular evasée. This is due to the fact that a rectangular evasée is subjected to shock losses. It is also found that the evasée must be of sufficient length so that the air is fully developed before it is discharged into the atmosphere. A proper transition piece between the fan outlet and the evasée is required. This study has certain drawbacks and limitations. Due to limited computation- memory, no mesh-independent and y-plus tests were performed in the simulations. Mesh sizes were kept constant along with enhanced wall treatment which was used for all simulations. |
