Axial Flow Fan Drawing


Fan design

All fans pull air in one side and blow it out the other side. This is achieved by the rotation of the blades (impeller), in general using an electric motor. There are 2 types of blades or impellers. The most commonly known is the propeller type, the second is a centrifugal blade, a blade shaped like a paddle wheel.

Fans using propeller type impellers (axial or inline fans)

Examples include the Industrial Fans, Mancoolers, Compact Air Blasters, Factory Floor Fans, Wall Exhaust Fans, Roof Exhaust Fans. The blades of the impeller are set at an angle to the direction of rotation (this is called pitch). As the impeller rotates, the blades cut the air on an angle and this creates high pressure in front of the blade and low pressure behind the blade. This results in the air being sucked in the back and expelled out the front.

Fans using centrifugal impellors (centrifugal fans)

Examples include Portable Exhaust Blowers and Carpet Dryers. The impeller of the centrifugal fan works a little differently. It looks like a paddle wheel but the blades pull the air into the centre of the blade hub and then out the exhaust area. These types of fans are particularly good for high-pressure applications or applications involving dust or explosive gases as the motor does not come into contact with the airflow.

Fan Body Design

The body of the fans also affects the way in which the fan operates. If the body is long, the air forced forward will travel in a straight line and further. If the fan body is short, the air will be forced out at a greater angle and will travel less distance. There are special aerodynamic designs which can be incorporated into a fan to improve its performance. These designs are mainly for special applications and for general use these designs are not cost effective and so rarely seen.

You, as our customer, will not need to be involved in fan design, but you may be involved in assisting your customer in making a fan selection. Some of the things you should consider when discussing fans with a customer are as follows:

  1. Application (blow or exhaust)
  2. Volume of air to be moved (large or small area)
  3. Velocity of air required (distance air needs to travel)
  4. Noise restrictions (existing noise levels)
  5. Natural ventilation (doors and windows)
  6. What type of air (toxic, explosive, hot, cold)