There are several different types of centrifugal fans, each with unique design characteristics, performance capabilities, and benefits. Often referred to as blowers, these industrial fans are used for high-pressure applications by a variety of industries, as well as air pollution systems.
These fans work by increasing the pressure of an incoming airstream by turning a series of blades (impeller) mounted on a circular hub. This accelerates the air as well as changes the direction of the air flowing outward, often by 90 degrees. In addition, these fans produce a steady airflow.
Basic Types of Centrifugal Fans
Below are the six most common types of centrifugal fans, each with a unique blade configuration.
- Forward Curved Fan – Also known as a squirrel cage fan due to the wheel type, this fan’s impeller is forward and somewhat small. In addition, the blades curve in the same direction as the rotation of the wheel. Because the impeller, shaft, housing, and bearings are delicately made, there are some limitations for sustainability when used for industrial applications. However, this fan is great for low-speed and low-pressure applications.
- Backward Inclined Fan – There are three standard blade types for this fan, including curved single thickness, flat single thickness, and curved airfoil. In addition to being relatively heavy and larger, the blades are designed to move away from the rotation of the wheel. For operation, this fan produces the highest speed. It is also considered more efficient than other fan types. Usually, the backward inclined fan is the best choice for low-pressure and high-volume applications.
- Radial Blade Fan – This centrifugal fan is referred to as a paddle wheel fan because the impeller has many equally spaced flat blades that extend perpendicular to the direction of rotation for the wheel. Sometimes, this type of fan has side rims. The blades tend to be heavier, but they are also narrower and deeper compared to both forward and backward inclined blades. Producing medium to high pressure and being able to move a higher mass or volume of fluid, this fan is best suited for material handling.
- Airfoil Blade Fan – The blades of this fan are hollow and backward inclined. Therefore, the fan is ideal for handling large volumes of clean air while operating at static pressures that are low to moderate. This fan also runs at a greater speed and produces optimum efficiency compared to the backward inclined fan. Capable of handling large volumes of air, it is used in induced and forced draft fans required for a wide range of applications.
- Radial Tip Fan – These centrifugal fans have blades with a backward and curved configuration while cupping in the direction of rotation for the wheel. Although compact, the fan works great for applications of high-volume airflow in which the requirement for pressure is considerably high.
- Inline Fan – Inline centrifugal fans are rugged. In addition, the backward inclined wheels are actually enclosed in a tube-axial casing. This medium-duty fan is less efficient and, therefore, used primarily when low-pressure airflow is required.