[Key words] centrifugal fan; Energy saving and consumption reduction; reform

1、 Concept of centrifugal fan

Centrifugal fan is a kind of mechanical equipment that relies on the mechanical energy input from the outside to improve the pressure of internal gas and discharge the gas. It is a driven fluid machinery. This machine is widely used in many aspects, such as factories, tunnels, mines, vehicles, ventilation and cooling in buildings, cooling and ventilation of air conditioning equipment, household appliances and other equipment, grain drying and so on.

Working principle of centrifugal fan:

The working principle of centrifugal fan is similar to that of turbine compressor, because the internal gas flow rate is relatively low, resulting in the internal pressure change is not too large. Therefore, the gas can be treated as an incompressible fluid without considering the change of specific volume of gas. There are two types of centrifugal fans, namely left-hand and right-hand. The way to distinguish these two centrifugal fans is to face the past from one side of the motor. If the impeller rotates clockwise, it is a right-hand centrifugal fan, and vice versa.

According to the working principle of the fan, the air volume of the fan is directly proportional to the motor speed, the air pressure of the fan is directly proportional to the square of the motor speed, and the shaft power of the centrifugal fan is the product of the air volume and the air pressure value. Therefore, it can be calculated that the shaft power of the fan is directly proportional to the third power of the motor speed of the fan. The specific relationship is shown in the figure below. It is relatively backward. For example, V-belt, worm gear pair and other devices are widely used in fan transmission in Shanghai, and the transmission efficiency is relatively low; Second, due to the backward regulation method, many centrifugal fans also use the regulating valve for regulation, resulting in the low efficiency of the device.

（2） Non manufacturer factors

The factors that lead to the high energy consumption of centrifugal fan are not only their own component problems, but also other aspects.

First, the actual working point of the fan deviates from the expected high-efficiency working point. The energy consumption of the centrifugal fan is closely related to its working point. If the staff choose too much safety margin for the fan, or just blindly choose its high-grade performance area, it is easy to cause the rated air volume of the centrifugal fan to exceed the performance actually required in the work. At this time, it is only good to use throttling to increase the resistance, The increase of man-made resistance will naturally lead to the increase of energy consumption and the decrease of service efficiency of the fan.

Second, the matching motor capacity of the fan is too large. When purchasing centrifugal fans, centrifugal fans with high rated motor power are often selected, which is easy to cause great waste.

Third, the unreasonable design of the fan pipeline system will increase the resistance of the fan pipe network and increase the energy consumption of the fan. The use efficiency of the fan is reduced.

Fourth, improper adjustment methods are adopted in the use of centrifugal fan, which will reduce its working efficiency and increase energy consumption. In addition, improper management process will also cause excessive waste of electric energy.