Industrial Fans
Below are six of the more popular design of industrial fans:
Centrifugal Fans
There are six types of centrifugal fan wheels in common use. Listed in the order of decreasing efficiency, they are:
Centrifugal fans with airfoil (AF) blades
The centrifugal fan with AF blades has the best mechanical efficiency and the lowest noise level (for comparable tip speeds) of all centrifugal fans.
Centrifugal fans with backward-curved (BC) blades
BC blades are single-thickness steel blades but otherwise are similar to AF blades with respect to construction and performance. They have slightly lower efficiencies but can handle contaminated air streams because the single-thinkness steel blades can be made of heavier material than can be used for hollow airfoil blades.
Centrifugal fans with backward-inclined (BI) blades
There are two more popular variations of centrifugal fans with BI blades. i) SISW (single inlet, single width) centrifugal fan wheel with BI blades. These are more economical in production, but they are somewhat lower in structural strength and efficiency. ii) ISW with a scroll housing.
Incidentally, scroll housings are not always used in connection with centrifugal fan wheels. Centrifugal fan wheels can also be used without a scroll housing, in such applications as unhoused plug fans, multistage units and roof ventilators. An exception is FC centrifugal fan wheels. They require a scroll housing for proper functioning.
Centrifugal fans with radial-top (RT) blades
RT blades are curved, with good flow conditions at the leading edge. Only the blade tips are radial, as the 'radial-tip blades' indicates. RT wheels are used mainly in large sizes with wheel diameters from 30 o 60 in, for industrial applications, often with severe conditions of high temperature and light concentrations of solids.
Centrifugal fans with forward-curved (FC) blades
FC blades, as the name suggests, are curved forward, i.e. in the direction of the rotation. This results in very large blade angles and in flow rates that are much larger than those of any other centrifugal fans of the same size and speed. These fans tend to be used in small furnaces, air conditioners and electronic equipment, whenever compactness is more important than efficiency.
Centrifugal fans with radial blades (RBs)
Radial blades (RBs) are rugged and self-cleaning, but they have comparatively low efficiencies because of the non tangential flow conditions at the leading edge. These fans can handle not only corrosive fumes but even abrasive materials from grinding operations.
    
|
