离心通风机.pdf

Centrifugal fan 1 Centrifugal fan Figure 1: Components of a centrifugal fan A centrifugal fan (also squirrel-cage fan, as it looks like a hamster wheel) is a mechanical device for moving air or other gases. It has a fan posed of a number of fan blades, or ribs, mounted around a hub. As shown in Figure 1, the hub turns on a driveshaft that passes through the fan housing. The gas enters from the side of the fan wheel, turns 90 degrees and accelerates due to centrifugal force as it flows over the fan blades and exits the fan housing. [1] Centrifugal fans can generate pressure increases in the gas stream. Accordingly, they are well-suited for industrial processes and air pollution control systems. They are mon in central heating/cooling systems. ponents The ponents of a typical centrifugal fan include the fan wheel, fan housing, drive mechanism, and inlet and/or outlet dampers. Types of drive mechanisms The fan drive determines the speed of the fan wheel (impeller) and the extent to which this speed can be varied. There are three basic types of fan drives. [1] Direct drive The fan wheel can be linked directly to the shaft of an electric motor. This means that the fan wheel speed is identical to the motor's rotational speed. With this type of fan drive mechanism, the fan speed cannot be varied unless the motor speed is adjustable. Belt drive A set of sheaves are mounted on the motor