Industrial Blowers: Centrifugal vs Axial Flow Types
Industrial blowers produce air with increased pressure and flow for applications that require enhanced airflow. Industrial blowers are available in various configurations and types. The two primary configurations are Centrifugal and Axial flow.
Centrifugal Fans and Blowers:
Centrifugal fans consist of a fan wheel, known as an impeller, contained within a blower housing. The impeller typically consists of several blades arranged around a hub. In many cases, the hub is hollow and the air enters the blower through this hollow hub. On entering the hub, the air spins outwards due to the centrifugal force, which accelerates the air. This accelerated air enters the scroll-shaped blower housing and exits the housing with increased pressure. These blowers are typically driven by various means that are usually situated outside the blower housing. Some of the various drives used are electric motors, steam turbines, and various other prime movers. The increased pressure that they provide to the air is an ideal choice for various industrial purposes as well as climate control, however compared to axial fans, centrifugal fans are generally noisier.
There are different types of centrifugal fans and their classification is based on the blade orientation of the blower's impeller, for instance, three types of centrifugal fans are backward inclined, forward inclined, and radial.
In radial fans, the blades extend straight outward from the hub in a radial fashion. This type of fan is typically used in applications that require low air volumes, but high speeds and pressures. Plus they are also ideal for applications that are high in particulate matter in the air stream, since they are not as sensitive to dust build-up as the other centrifugal type fans.
Forward inclined and backward inclined fans are the other types of centrifugal fans. These blowers differ from each other based on the direction in which the blades curve away from the hub. While in forward inclined types, they are curved in the same direction as the impeller's rotation, in backward inclined fans the blades are curved in the opposite direction to impeller rotation. Backward inclined fans offer more energy efficient operation than radial fans and are ideal for applications that require moderate specific speeds, i.e. applications with medium airflow and high-pressure. Forward inclined fans, on the other hand, are typically used for applications that require high airflow rates, while high pressure is not of consequence.
Axial Fans and Blowers:
Axial fans, another type of industrial blower, consist of fan wheels that direct air along the axis of fan rotation. They are available in a wide range of sizes and have been adopted in various applications ranging from large fans in wind tunnels to cooling fans in electronic items and computers. Another good example of axial fans that are in everyday use are ceiling fans. The axial fans also have various drive options and they can also be classified based on their blade type.
One type of axial fan is the variable pitch fan with movable blades. By changing the pitch of the fan, the user can control the airflow rate. Another variation of this fan is one that can change the fan pitch while the fan is rotating. Axial fans typically offer significantly higher efficiencies as compared to centrifugal fans. In fact, in many cases, the stated efficiencies of centrifugal fans are lower than actual on-field efficiencies.
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