A centrifugal fan is a machine that uses input mechanical energy to increase gas pressure and discharge gas; it is a type of driven fluid machinery. Centrifugal fans are widely used in factories, mines, tunnels, cooling towers, vehicles, ships, and buildings for ventilation, dust removal, and cooling; in boilers and industrial furnaces for ventilation and induced draft; in air conditioning equipment and household appliances for cooling and ventilation; in grain drying and conveying; as a wind source for wind tunnels and for inflating and propelling hovercraft, etc.
Centrifugal fans operate on the principle of converting kinetic energy into potential energy. A high-speed rotating impeller accelerates the gas, then decelerates and changes its flow direction, converting kinetic energy into potential energy (pressure). In a single-stage centrifugal fan, gas enters the impeller axially, changes to radial flow as it passes through the impeller, and then enters the diffuser. In the diffuser, the gas changes its flow direction, and the increased cross-sectional area of the pipe slows the airflow; this deceleration converts kinetic energy into pressure energy. The pressure increase mainly occurs in the impeller, and secondarily in the diffusion process. In multi-stage centrifugal fans, a return flow device is used to direct the airflow into the next impeller, generating higher pressure.
