Centrifugal, axial and double stage fans: a tecnical classification

High-pressure double stageIn post “Industrial Fans explained to the laymen/ non insiders”, we have provided a very simplified description of the industrial fans, and we have added an essential classification too. In this post we want to provide a more technical explanation, defining the industrial fans with more specialized terms and classifying them accordingly.

In this situation, we can define the industrial fan (hereinafter: fan) as a turbomachine that receives mechanical energy and then uses it, thanks to a bladed impeller, in order to maintain a continuous flow of air or other gas passing through it, providing a work per unit mass that is not greater than 25 kJ / kg (UNI EN ISO 13349).

There are several ways of classifying industrial fans:

Classification based on the performance of the flow in the impeller:

  • Centrifugal fans: in these fans the fluid enters the impeller with axial direction and leaves it in a direction perpendicular to the axis. The double stage is a particular configuration of the centrifugal fans (see the image in evidence) in which two impellers and therefore two different stages of compression are used;
  • Axial fans: in these fans the air enters and exits the impeller along surfaces that are cylindrical and coaxial with the same fan.

Classification based on the drive system:

  • Belt driven Fan
  • Direct driven Fan (directly coupled with the electric motor)
  • A particular system is the system with the coupling joint; it typically consists of a female plus a male part. The female part is installed with a plug to the bearing block, differently the male one is installed to the shaft of the electric motor.

Classification based on the maximum pressure delivered:

  • Fans with low pressure (maximum pressure delivered: about 300 mmCA)
  • Fans with medium pressure (maximum pressure delivered: about 600/700 mmCA)
  • Fans with high pressure (maximum pressure delivered: about 2500 mmCA)

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