The working principle of the centrifugal backward curved fan is basically the same as that of the turbo compressor. It is used because the gas flow rate is low and the pressure does not change much. Generally, it is not necessary to consider the change of the gas specific volume when using the gas. The compressed fluid is being processed. After centrifugation, the curved fan can be made into two types: right-handed and left-handed. Looking from the side of the motor: the impeller rotates clockwise, called the right rotary fan, and the impeller rotates counterclockwise, called the left rotary fan.
After centrifugation, the gas enters the impeller from the axial direction during the operation of the curved fan, and the gas changes to a radial direction as it flows through the impeller, and then enters the diffuser. In the diffuser, the gas changes the direction of flow and the cross-sectional area of the pipe increases to slow the flow. This deceleration converts kinetic energy into pressure energy. The increase in pressure mainly occurs in the impeller, followed by the expansion process. In a multistage centrifugal fan, a return flow is used to direct the gas flow to the next impeller, resulting in higher pressure.
When testing the fan after centrifugation, start the low speed and check whether the rotation direction is correct. When starting the high speed, the fan must be restarted before starting to prevent the high speed reverse rotation, causing the switch to trip and the motor to be damaged. When the centrifugal fan reaches the normal speed, the input current of the fan should be measured. The operating current of the centrifugal fan cannot exceed its rated current. If the operating current exceeds its rated current, check that the supplied voltage is normal.