Axial Fan Impellers

This article will give you an understanding of systems that utilize axial fan impellers. An Axial fan is a type of air handling device which generates the flow of a gas or air along the same direction of the axis that the impeller or prop is mounted on. A simple example of an axial fan is a domestic cooling fan or a radiator fan. Some Axial fans have impellers which generate air from the interior. An Impeller is a device consisting of blades or ribs, which rotate to generate the movement of air, fluid, gas or particles within a housing or tube. The difference between a propeller and an impeller is that the propeller does not have a housing or tube to help control the volume and pressures around it. Impellers should rotate as close to the housing as possible to ensure the highest efficiency.

What is an Impeller?

Impellers are used in many domestic devices such as the washing machine. Heavy duty axial fan impellers are usually constructed of high-pressure die cast of aluminum to resist corrosive gases, fluids or particles that may come in contact with the blade, and cause chemical reactions. The chemical property of aluminum ensures that the fans are both lightweight while maintaining tensile strength. Impellers have to be balanced and properly designed with computer aided design and machine tools to ensure that they do not vibrate, and that they operate as smoothly as possible.

Types of Impellers

There are two types of impellers at Custom Fans of Australia, these are Fixed Pitch Impellers and Variable Pitch Impellers. The Pitch of an impeller is the angle at which the blades are to the axis of the shaft that the impeller rotates on. It defines how much air and how high the pressure is, when the fan is in operation. Fixed Pitch Impellers are fixed and do not have a change in the angle of the impellers unless they are warped by an external factor. Variable Pitch Impellers can vary the angle of the impeller with a rod or motor which is attached to the base of each blade or fin.

Impeller Shapes

The shapes of the blades on impellers can vary to fit applications and certain criteria. Some of the shapes of impellers are Sickle Shaped, Airfoil Shaped, Increasing Circular Shaped, Uniform Circular Shaped, Reversing Arc Shaped and the Plastic Fan shaped.

The Sickle Shaped Impeller is designed for reduced noise and high pressures. Each blade is shaped like the sharp end of a sickle.

The Airfoil Shaped Impeller is slim and slightly thinner at the circumference. This is a versatile impeller that is a great application for varying conditions. Airfoil impellers can have six, eight or nine blades on it at a time.

The Increasing Circular Shaped impeller is great for locations where the airflow direction is conflicting. A perfect application is on a car engine or radiator where the airflow varies due to the change in temperatures.

The Uniform Circular Shaped impeller has very thick and rectangle shaped blades, and are great for pushing a high amount of air at very low speeds.

The Reversing Arc Shaped is used for applications where the direction of rotation sometimes changes. It has the same schematic design as the airfoil shaped impeller, but it can change the direction. A great application of this type of impeller is an HVAC ventilator that needs to regulate the humidity or temperature by pulling air out or pulling in more air.

The Plastic Fan Shape is a reduced price impeller which is light and affordable.

The blades are connected to the shaft with a Hub and Boss. The type of Hub that is applicable depends on the amount of blades the impeller will use. The Boss can be forged, connected with a bushing, or made from pressured die-cast aluminum or bar stock. Axial fan impellers come in all shapes and sizes and can be applied to many fan systems.