Centrefugal Fan

This fan looks like a wheel a hamster would use. It is sometimes called a squirrel cage fan its purpose is to move gases or air. The fan wheel is composed of a number of fan blades or ribs. These are around a hub. The hub itself turns on the driveshaft and passes through the fan housing. When air or gas enters from one side or the other of the fan wheel, it will turn ninety degrees and speeds up because of the centrifugal force.

The centrifugal fan can make a lot of pressure that rises in the gas stream. Central air in heating and cooling conditioners is a common place they will be found. Another place a centrifugal fan can be found is in some air pollution systems, as well as in large warehouses.

Major components of a centrifugal fan is the drive mechanism, fan housing, the wheel fan and inlet and or outlet dampers. The fan drive of a centrifugal fan determines the rotation of the speed the fan wheel and how much the speed can be changed. There are just three types of fan drives on a centrifugal fan. The fan wheel can be hooked up to the shaft of an electric motor, meaning the wheel speed is as fast as the motor’s rotational speed. This type of drive mechanism, the fan speed cannot be changed unless the motor speed is able to be changed.

Many different belts are used in belt driven fans. On a centrifugal fan those belts rotate in a set of wheels that have grooved rims for holding the belts. These are mounted on the motor and fan shafts. These belts will take mechanical energy from the motor to the fan.

The other one is the fan wheel rotational speed. On the centrifugal fan, this is expressed in revolutions per minute or RPM. This depends on the ratio of the motor grooved rims diameter to the fan wheel diameter grooved rim.

Centrifugal fan performance ratings are very strict in the United States. They are from the manufacturers of the centrifugal fan. Tabulations would be the discharge of static pressure that is created, as SP in inches of water. One inch of water pressure is 258.8Pa. Volume of the standard air; that is being used in cubic feet per minute, CFM. The centrifugal fan ratings on performance and the power amount that is provided by the fans drive motor, or brake horsepower, BHP.

Bearings are very important on a centrifugal fan, just as the blades are. Called sleeve ring oil bearings, these may be water cooled. If water cooled the sleeve bearings are used as the hot gases will be moved by the centrifugal fan. Heat then is carried out through the shaft and into the oil. Heat is high and must be cooled to prevent overheating of the bearing. Bearings are an important part of a fan.

There must be fan dampers on a centrifugal fan, as it used to control the gas flow in and out of the fan. The dampers on the outlet side gives a resistance flow that is used to control the gas flow. The damper on inlet side controls the gas flow by the amount of gas or air let into the fan inlet.