The centrifugal fan is a driven fluid machine that relies on the mechanical energy input to drive up the gas pressure and discharge the gas. Centrifugal fans are widely used in ventilation, dust removal and cooling in factories, mines, tunnels, cooling towers, vehicles, ships and buildings; ventilation and induced draft in boilers and industrial furnaces; cooling and in air conditioning equipment and household appliances. Ventilation; drying and selection of grain; air source of wind tunnel and inflation and propulsion of hovercraft, and etc.