First, the principle of centrifugal fan Prime mover driven impeller rotates, the axial gas into the impeller, when the gas leaves through the rotating impeller that, since the effect of forcing the leaf blades of the gas channel with the rotation, the centrifugal force, these gases being left to the chassis, in the the process gas for energy, the gas pressure increased and the kinetic energy increases, the energy gained when the gas is sufficient to overcome the resistance of the system when the gas can be transported to the height or distance; At the same time the inlet of the impeller reduce the gas density , which leads to lower than outside pressure, in which the role of outside pressure air into the impeller. Cycle, continuous operation since the impeller, a continuous outflow of gas is discharged, so as to achieve a continuous fan of gas transportation purposes. This shows that the fan is a centrifugal force produced by the rotation of the impeller under the action of the mechanical energy into pressure energy and function of the gas machinery. International Organization for Standardization is the latest definition of fan: fan is a continuous flow of gas to maintain rotating machinery. Second, the characteristics of centrifugal fan 1) Most of the impeller and the casing structure with steel plates welded or riveted; 2) The speed is low, generally n <3000 rev / min; 3) production volume, for ease of production and maintenance, mostly used in the design of rolling bearings. Third, the fan of the main performance parameters 1, the pressure Boost pressure is the fan, the fan into the outlet of the pressure difference. Usually given in the design of performance parameters when selection is the total pressure, in units of Pa. 2, the volume flow Fan volume flow is the volume of imports of the state of flow, in units of M 3 / H, as the unit of time the volume of gas flowing through the fan. 3 temperature Degree of temperature is a sign of hot and cold gas, is demanding to know when the fan design and selection of the most important parameter, is to calculate the pressure, select the impeller, an important material basis for the spindle. International Temperature Scale: t, unit °C Absolute temperature scale: T, Unit K T=273.15+t T = 273.15 + t Fourth, the structure of the formation of fan Part Name Remarks Impeller It is stressful fan main components of energy transfer from the former plate, composed of leaves and the back plate. Inlet In the case of minimum loss, even the gas into the impeller. Case It is collected out of the gas from the impeller, driven exhaust port, and will air part of the kinetic energy into pressure energy. It mostly rectangular cross section. Adjusting the door By adjusting the opening to control air flow. Airbox Generally used in large-scale double-suction fan, that is imported to improve the flow conditions, and easy to install and maintain and improve the bearing operating conditions. Shaft drive The impeller fixed to the spindle. Spindle Power transmission shaft Worm tongue Affect the efficiency and noise Leaves The mechanical energy into the energy of the gas Diffuser In order to minimize energy loss in the case of some of the kinetic energy into pressure energy.