Fans are essentially used to circulate air around to cool your immediate surroundings. With the advancement of technology, the role of fans has gotten wider. Today, fans are being designed in such a way that they play pivotal roles in aviation and automotive energy production. A centrifugal fan is a great example.
Also known as centrifugal blowers, centrifugal fans are widely used in a variety of applications as they have a simple construction and are much more cost-effective than axial fans. These fans are very popular in the HVAC (Heating, Ventilation, and Air Conditioning) industry and make excellent air pollution control systems.
How do Centrifugal Blowers and Fans Work?
The primary function of centrifugal blowers and fans is to rapidly escalate the movement of air/gas/liquid that passes through them.
A typical centrifugal blower comprises of a fan housing, impellers, inlet and outlet ducts, a drive shaft, and a driving mechanism. As the air enters the fan housing through the inlet duct, it is driven towards the centre of the impeller. The driving shaft, aided by the driving mechanism, causes the impellers to rotate. The kinetic energy created due to the rotation of the impeller blades imparts an increased volume of speed to the air which is finally released from the outlet duct at high speed.
The driving mechanism behind centrifugal fans and blowers is one of the most important parts of the entire arrangement as it is this force that causes the impeller blades to rotate. There are two types of driving mechanisms: direct drive and belt drive mechanism.
In the direct drive mechanism, the drive shaft is connected to an electric motor. This entails that the speed of the centrifugal blower and fan can be controlled and altered by controlling the speed of the motor. Contrary to this, in the belt drive mechanism, a set of sheaves are mounted on the motor shaft, and a belt is used to transfer the mechanical energy from the motor to the drive shaft. In this arrangement, the fan speed depends upon the ratio of the diameter of the motor sheaves to the diameter of the fan wheel. Through these two are the most commonly used methods in centrifugal blowers and fans, some models even use hydraulics and magnetic coupling as driving mechanisms.
A centrifugal blower can either be single or a multi-stage unit with different blade orientations: radial, forward curved and backward curved. While a single stage centrifugal blower is used for applications that require a uniform airflow, a multi-stage blower is used for applications that demand varying airflow at a constant pressure.
Depending on their pressure generation ability, centrifugal blowers are classified into three types: low pressure, medium pressure, and high-pressure centrifugal blowers.
Usage and Purpose of Blower Fans
- Centrifugal blowers and fans are widely used in large and small scale industries by their virtue of speeding up the airflow in large volumes.
- Centrifugal fans that are radially tipped and backward inclined are used for dust collection purposes.
- Industrial applications that involve chemical processing require centrifugal blowers to channel the corrosive and hazardous chemicals out of the building to prevent corrosion of machinery.
- Centrifugal fans are used for material handling (sand, plastic pellets, sawdust, wood chips, grain, paper trim, etc.) purposes.
- They are also used in superchargers in automobiles. Heavy muscle cars usually get their extra power from superchargers equipped with centrifugal fans and blowers. As the air enters the supercharger, the fan imparts a high speed to the airflow that when coupled with a powerful fuel, can produce a strong combustion power.
What Are Industrial Blower Fans?
The industrial blower fan is a term coined for large and bulky centrifugal blowers and fans. These are used in industries to deliver a large volume of airflow, and this is achieved through an arrangement of powerful impeller blades that rotate at a high rpm aided by the driving mechanism.
These fans have diverse functionalities and can be used for combustion, aeration, ventilation, exhaust, particulate transport, cooling, air-purification, and drying purposes. They are commonly used in heavy duty industries such as the electrical power production, pollution control, metal manufacturing, cement production, and petrochemical, to name a few.
Types Of Centrifugal fans
Centrifugal fans can be classified into four categories based on their blade designs.
- Airfoil BladeThese fans come with hollow, airfoil blades that have been specially designed to utilize the energy of airstreams. They are highly efficient and quieter.
- Radial BladeThese types of centrifugal fans have flat blades that are arranged radially. Though they generate high pressure, the airflow is moderate. These fans are great for industrial applications that create a lot of dust, or in environments that tend to get very humid and moist.
- Forward CurveThe blades are slightly curved are these generate medium pressure with high airflow. They are ideal for bringing in clean air, ventilating and exhaust applications.
- Backward CurveThese are curved backwards and very efficient. They generate high airflow along with high-pressure.