According to the principle that kinetic energy is converted into potential energy, centrifugal fan uses high-speed rotating impeller to accelerate the gas, then decelerates and changes the flow direction, so that kinetic energy is converted into potential energy (pressure). In a single-stage centrifugal fan, the gas enters the impeller from the axial direction, changes to the radial direction when passing through the impeller, and then enters the diffuser. In the diffuser, the movement direction of the gas is changed and the cross-section area of the pipe is increased to slow down the gas flow.
This deceleration converts kinetic energy into pressure energy. The increase of pressure mainly occurred in the impeller, followed by the expansion process. In the multistage centrifugal fan, the air flow is sent into the next impeller with a reflux device to produce higher pressure. Centrifugal fan is essentially a variable flow and constant pressure installation. When the rotating speed is fixed, the theoretical curve of pressure flow of centrifugal fan should be a straight line. Due to internal losses, the practical characteristic curve is curved. The pressure produced in the centrifugal fan is greatly affected by the change of inlet air temperature or density.
For a given intake volume, the highest intake temperature (lowest air density) produces the lowest pressure. For a given pressure and flow characteristic curve, there is a power and flow characteristic curve. When the blower is running at a constant speed, the required power increases with the decrease of inlet air temperature for a given flow.
The wear problem of the transmission part of the centrifugal fan is a common equipment problem, including the wear of the bearing position of the suction fan, the bearing chamber, and the bearing position of the blower shaft. In view of the above problems of centrifugal fan, the traditional maintenance methods include overlay welding, thermal spraying, brush crossing, etc., but all of them have some disadvantages: the thermal stress generated by high temperature of repair welding can not be completely eliminated, and it is easy to form material damage, resulting in bending or fracture of parts; while brush plating is subject to the limitation of coating thickness, which is easy to peel off.