Axial fans are vortex machines driven by an electric motor, in which the direction of the air (or mixture of other gases) flow is parallel to the axis of rotation of the impeller installed within it. In other words, the movement occurring inside the housing follows the direction of the duct casing axis system and the axis of the rotating motor shaft.
Axial fans are divided into: single-stage and multi-stage, where multi-stage can be either co-rotating or counter-rotating.
The main component of a fan is the impeller, which defines its operating parameters and thus the possibility of using a particular type of fan in a suitable installation. The impellers in most axial fans are unidirectional. There are also fans equipped with bidirectional or reversible impellers. Unidirectional impellers in medium- and high-pressure fans often work with a rear wheel or with a front and rear wheel. Reversible impellers, on the other hand, are those where a change in the return of the flowing air takes place (the axial direction remains the same). The change in air return is mainly due to a change in the direction of rotation of the motor shaft on which the impeller is placed.
Axial fans are mainly used in installations where large volumes of air must be pumped at low flow resistance. However, there are installations where large air volumes have to be handled with high resistance. Medium-pressure or high-pressure axial fans are then used. The design of the impeller blade of a medium-pressure or high-pressure axial fan is different from that of standard low-pressure axial fans. The pressure increments in axial fans can then be similar to those found in radial fans.