During the operation of centrifugal fan, according to the principle of converting kinetic energy to potential energy, the centrifugal fan effectively uses its high-speed rotating impeller to accelerate and slow down the gas and change its flow direction effectively, so that kinetic energy can be converted into potential energy (pressure). In a single stage centrifugal fan, the gas enters the impeller from the axial direction, changes to radial direction when the gas flows through the impeller, and then enters the diffuser.
In the diffuser, the gas of the centrifugal fan changes the flow direction and increases the cross-section area of the pipe. This deceleration converts kinetic energy into pressure energy. The increase of pressure mainly occurs in the impeller and then in the process of expanding pressure. In a multi-stage centrifugal fan, air flow is driven into the next impeller with a return flow, resulting in higher pressure.
The power required by centrifugal fans during start-up is usually several times the normal operating power. The starting power of centrifugal fan is the smallest when the fan valve is completely closed (the air volume is close to zero), and the maximum when the valve is fully open (maximum air volume). Therefore, in order to ensure the safety of the motor, the valve should be closed first when the centrifugal fan starts.
Centrifugal fan speed increased to the working speed, and then gradually opened the valve. Otherwise, the motor is in danger of being burned out due to excessive starting load. In the course of operation, the bearing and motor bearing temperature of fan spindle should be checked in time. The temperature rise of the bearing is generally not allowed to exceed 40 ℃. When the ambient temperature is not more than 40 ℃, the alarm temperature of the fan bearing is 80 ℃, and the alarm temperature of the motor bearing is 85 ℃.