A centrifugal fan is a passive fluid machinery that, with the input of mechanical energy, increases gas pressure and expels it.
Centrifugal fans are widely used in factories, coal mines, tunnels, cooling towers, vehicles, ships, and buildings for ventilation, dust extraction, and cooling; for ventilation and exhaust in boiler and industrial furnace; cooling and ventilation in air conditioning systems and home appliances; and grain drying and selection.
Centrifugal fans operate based on the principle of kinetic energy being converted into potential energy. They accelerate the gas by using high-speed rotating blades, then decelerate and change the inflow direction, converting kinetic energy into potential energy (pressure). In single-stage centrifugal fans, the gas enters the impeller radially and changes direction to axial as it passes through the impeller, then enters the diffuser. In the diffuser, the gas alters its flow direction and the increased cross-sectional area of the pipeline slows down the gas flow, converting kinetic energy into pressure energy. The pressure increase is primarily achieved in the impeller, followed by the diffusing process. In multi-stage centrifugal fans, a return conduit is used to direct the swirl into the next impeller, generating higher pressure.
Effectiveness
The working principle of centrifugal fans is essentially the same as that of turbine compressors. Both operate under the premise that the gas flow rate is low, resulting in minimal pressure changes. Generally, the change in specific volume of the gas should not be considered, and the gas can be treated as an incompressible fluid for resolution.
Centrifugal fans can be manufactured in two types: right-rotating and left-rotating. When viewed from the motor side, if the impeller rotates clockwise, it is known as a right-rotating fan; if it rotates counterclockwise, it is known as a left-rotating fan.
