Centrifugal fans are mechanical devices that increase gas pressure and discharge gases by utilizing input mechanical energy, making them a type of driven fluid machinery. They are widely used for ventilation, dust removal, and cooling in factories, mines, tunnels, cooling towers, vehicles, ships, and buildings; for ventilation and exhaust in boilers and industrial furnaces; for cooling and ventilation in air conditioning equipment and household appliances; for drying and selection of grains; for wind tunnel air sources and air cushion ship inflation and propulsion, etc.