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The function and structure of centrifugal fan
During the operation of the centrifugal fan, according to the principle of converting kinetic energy into potential energy, the gas is accelerated by the high-speed rotating impeller, then decelerates, changes the flow direction, and converts the kinetic energy into potential energy. energy (pressure). In a single-stage centrifugal fan, the gas enters the impeller from the axial direction, becomes radial as it flows through the impeller, and then enters the diffuser. In a diffuser, the flow direction of the gas changes and the cross-sectional area of the pipe increases, which slows the gas flow and converts kinetic energy into pressure energy. The pressure increase occurs mainly in the impeller, followed by the diffusion process. In a multi-stage centrifugal fan, the airflow passes through the return device to the next impeller and creates a higher pressure.
Due to the low gas flow rate and small pressure change, the change in the specific volume of the gas is usually not considered, that is, the gas is treated as an incompressible fluid. From the motor side, centrifugal fans can be divided into right-handed and left-handed: the impeller rotates clockwise, called right-handed fan; the impeller rotates clockwise, called right-handed fan. The impeller rotates counterclockwise and is called the left fan.
The structure of the centrifugal fan
Centrifugal fan consists of shell, main shaft, impeller, bearing transmission mechanism and motor, etc. Shell: made of steel plate, strong and reliable, can be divided into integral type and semi-open type, and the semi-open type is easy to maintain
Impeller: Consists of blades, curved front plate and flat rear plate
Rotor: should be statically and dynamically balanced to ensure smooth rotation and good performance. Transmission part: It consists of main shaft, bearing box, rolling bearing and pulley (or coupling).
Centrifugal fans are essentially variable flow and constant pressure devices. Under constant speed conditions, the theoretical pressure flow curve of the centrifugal fan should be a straight line, while the actual characteristic curve will be curved due to internal losses. The pressure generated by a centrifugal fan is greatly affected by changes in inlet temperature or density. For a given intake air, the air temperature (low air density) produces lower pressure. For a given pressure and flow characteristic, there is a power and flow characteristic. When the blower is running at a constant speed, at a given flow, the required power increases as the intake air temperature decreases.