When the fan is working, the air flow enters the blade space from the axial direction of the fan, and then rotates with the impeller under the drive of the impeller. On the other hand, under the action of inertia, improve the energy, leave the impeller along the radius direction, and rely on the centrifugal force to do work called centrifugal fan. The centrifugal fan is mainly composed of air inlet, air valve, impeller, motor and air outlet. In different states, the effect of centrifugal fan is not the same. Centrifugal fans are widely used in factories, mines, tunnels, cooling towers, vehicles, ships and buildings for ventilation, dust removal and cooling; Ventilation and ventilation of boilers and industrial furnaces; Cooling and ventilation in air conditioning equipment and household electrical equipment; Drying and selection of grains; Wind tunnel wind source and hovercraft inflation and propulsion, etc. With the application of centrifugal fan more and more wide, all kinds of deficiencies and problems are beginning to be found and improved one by one. However, only finding problems and then improving them can no longer meet the needs of the rapid development of the market. The development of centrifugal fan must be based on the premise of meeting the market demand, to be innovative, and develop a new type of centrifugal fan to promote the development of the market. But overall the development of centrifugal fan is towards the direction of low energy consumption, low noise and high efficiency.