A centrifugal fan is essentially a variable flow rate, constant pressure device. At a constant rotational speed, the theoretical pressure-flow rate curve of a centrifugal fan should be a straight line. However, due to internal losses, the actual characteristic curve is curved. The pressure generated in a centrifugal fan is significantly affected by changes in inlet air temperature or density. For a given inlet air volume, the pressure is lowest at the highest inlet air temperature (lowest air density).
For a given pressure-flow rate characteristic curve, there is a power-flow rate characteristic curve. When the blower operates at a constant speed, for a given flow rate, the required power increases as the inlet air temperature decreases. The working principle of a centrifugal fan is basically the same as that of a turbine compressor. Because the gas velocity is low and the pressure change is small, changes in gas specific volume are generally not considered; that is, the gas is treated as an incompressible fluid.
Centrifugal fans can be manufactured in both right-hand and left-hand rotation types. Viewed from the motor side: if the impeller rotates clockwise, it is called a right-hand rotation fan; if the impeller rotates counterclockwise, it is called a left-hand rotation fan.
