Working principle of fan

The working principle of a fan relies on the input mechanical energy to increase gas pressure and deliver gas.
A fan is a passive fluid machinery that operates on the same principle as a turbo compressor. However, due to the low gas flow rate and minimal pressure changes, there is generally no need to consider changes in gas specific volume, treating gas as an incompressible fluid. The performance parameters of a fan mainly include flow rate, pressure, power, efficiency, and speed. In addition, the magnitude of noise and vibration are also major design indicators for fans. Flow rate, also known as air volume, is expressed as the volume of gas flowing through a fan per unit time. Pressure, also known as wind pressure, refers to the increase in pressure of gas inside a fan, which can be divided into static pressure, dynamic pressure, and total pressure. Power refers to the input power of the fan, that is, the shaft power. The ratio of the effective power of a fan to the shaft power is called efficiency. The total pressure efficiency of the fan can reach 90%.
According to the direction of gas flow, fans can be classified into centrifugal, axial, diagonal, and cross flow types. The following introduces the working principles of two common types of fans:
1.The working principle of a centrifugal fan is to use a high-speed rotating impeller to accelerate gas, then decelerate and change the flow direction, converting kinetic energy into potential energy (pressure). In a single-stage centrifugal fan, gas enters the impeller from the axial direction, changes to the radial direction as it flows through the impeller, and then enters the diffuser. The increase in pressure mainly occurs in the impeller, followed by the expansion process. In multi-stage centrifugal fans, a reflux device is used to direct the airflow into the next impeller, generating higher pressure.
2.The working principle of an axial flow fan is that, like an electric fan, the blades of this fan have an angle with the fan shaft. When rotating, the blades push the air along the axis towards the air outlet, creating a certain negative pressure at the air inlet, and new air is replenished, thus maintaining normal operation.