Centrifugal fans and axial fans share the same purpose for ventilation and heat dissipation of equipment.
1. In principle
1. The principle of centrifugal fan: the air flow axially flows into the rotating blade channel, and is thrown to the outer edge of the impeller under the action of centrifugal force, and is discharged from the air outlet.
2. The principle of axial flow fan: the gas enters the rotary vane axially and is pressurized before being discharged axially from the other side.
1. Centrifugal fans are generally composed of impeller, casing, current collector, motor and transmission parts (such as main shaft, pulley, bearing, V-belt, etc.). The impeller consists of a disc, blades (the number of blades is generally 8 to 16), a wheel cover, and a shaft disc. The casing consists of a volute plate, side plates and outriggers. Centrifugal fans can use forward or backward blades, which can adapt to a wider range of air volume and pressure requirements. Moreover, the cabinet can be muffled, which has obvious advantages in noise indicators. The motor and the fan are generally connected by a shaft.
2. The axial flow fan is generally composed of impeller, casing, current collector and motor. The impeller is composed of blades and hub, and the casing is composed of fan duct, frame plate and bracket. The blade diameter of an axial fan is limited to the diameter of the casing. The motor is usually inside the fan.
3. Air volume and air pressure
1. The centrifugal fan has a high pressure coefficient and a relatively low flow coefficient. According to the pressure level, it is divided into high pressure (15000 ~ 3000Pa), medium pressure (3000 ~ 1000Pa), and low pressure (<1000Pa).
2. The axial flow fan has the characteristics of low pressure and large flow, and is divided into high pressure (500 ~ 5000Pa) and low pressure (<500Pa) according to the pressure level. Low pressure is mainly used for ventilation in general places.
Centrifugal fans are often installed at the inlet and outlet of air-conditioning units, boiler drums, induced draft fans, etc. The installation is more complicated, while the installation of axial fans is often in the middle of the air duct or at the front of the air duct outlet.