A centrifugal fan impeller or blower wheel is the muscle of a centrifugal fan. It is the part of the fan that sucks air then pushes it perpendicularly towards an outlet following a centrifugal motion. Of course muscles cannot work without a brain. This is why the motor is still the most essential part of a centrifugal fan.
The types of centrifugal fan are identified mainly by the kinds of impeller they use. By simply looking at the physical structure of impeller inside a centrifugal fan, you will be able to know the kind of fan at hand.
Types of Centrifugal Fan Impeller
Basically, there are three general types of centrifugal fan impellers that Custom Fans designs: forward, backward and radial. But with the constant advancements in industrial technology, manufacturers have come up with different variations out of these three basic types. Thus impellers which are more specific in terms of purpose and specification were born – bringing along with them more sophisticated names. Common centrifugal fan impellers can now be classified into six specific types: shrouded radial blade, open radial blade, open paddle wheel, backward-inclined, forward curved multi-vane and backward curved radial.
Each of these impellers has their own specialization and distinct characteristics. Depending on the purpose and situation, one impeller might prove to be more suitable over the other. The key is on knowing what each impeller is primarily designed for and on what situation and environment it will mostly be used.
- Shrouded Radial Blade
Pressurizing, blow-off systems and long duct or pipe runs are where this type of impeller is most commonly used. It is designed primarily for delivering higher pressure.
- Open Radial Blade
This type of impeller is designed for conveying powdery or granular material and long stringy paper trimmings or fibres
- Open Paddle Wheel
Similar to Open Radial Wheel, this impeller is also used for conveying powdery or granular material.
- Backward Inclined (with flat blades or air foil blades)
This type is commonly used for general ventilation, forced cooling at higher pressures and in dust collection systems where the fan is on the clean air side of the dust collector
- Forward Curved Multi-vane (squirrel cage)
Most notable for its structural similarities with that of a squirrel cage, this impeller type is designed for moving large volumes of air at lower pressures. This type is also typically used for general ventilation and forced cooling at slower speeds.
- Backward Curved Radial
This impeller is a modified version of the Open Radial Blade Wheel. It is designed to expand the performance ratings of open radial bladed wheels in some direct driven fans. It can also be used to convey granular material but should not be used to convey powdery or stringy ones.
Centrifugal Fan Impeller Drive Mechanism
Centrifugal fans may employ one of three drive mechanisms: direct, belt, or variable drive. The drive mechanism that governs a centrifugal fan is the primary basis of the fan speed and speed variation.
Direct drive, as its name suggests, is characterized by the direct linkage of the fan impeller to that of the motor shaft. Thus, the resulting speed of the fan is the same with that of the motor shaft; offering no means for variety.
Meanwhile, in a belt drive setup, the fan impeller and motor shaft are connected by one or more belts. In result, the speed of the fan depends upon the ratio of the sizes of both the motor shaft and the fan impeller.
Lastly, variable drive allow for flexible fan speeds with the help of hydraulics and magnetic couplings.
Ideal Composition of a Centrifugal Fan Impeller
In choosing a centrifugal fan, you must consider the composition of the centrifugal fan impeller. Knowing what an impeller is made of is just as important as knowing any other specification of a centrifugal fan.
For example, if you are going to use a fan in corrosive environments, impellers made of galvanised steel or ‘316’ stainless steel must be used to prevent rusting.
The Bottom Line
Centrifugal fans offer a big lending hand in many important industries including the grain aeration industry. Whenever massive ventilation and pressure are to be dealt with, seeking assistance from this type of fans is usually the most logical and economical way. And because they play such a major role, it is imperative to check and know every detail of them before buying. A good way to start is at the centrifugal fan impeller.