A fan that consists of several streamlined blades mounted in a revolving
casing. The cross section and spacing of the blades are designed
aerodynamically. This design ensures that the air flows without recirculation
between the blades and leaves the rotor in a steady and regularly distributed
stream. This appreciably reduces frictional, conversion, and recirculation
losses. Fans of a convenient size can handle large volumes of air at the
highest pressures likely to be required in mine ventilation.
Source: Dictionary of Mining, Mineral, and Related Terms