Reasons for axial fan surge

Hello everyone, Xiaobian came to popularize knowledge for everyone. It mainly talked about the three parts of the surge of the axial fan, the wind of the axial fan and the stall of the axial fan. Once the content is too much, the small editor decides For everyone to talk about, first of all, let us first look at the reasons for the surge of axial fans, look down

Axial fan surge:

The surge of the fan refers to the phenomenon that the fan causes a large fluctuation of the air volume, pressure and current during the operation of the unstable zone, the noise increases, and the fan and the pipeline vibrate violently.

As long as the operating point does not enter the above unstable zone during operation, the fan surge can be avoided. When the installation angle of the rotor is changed, the K-point changes accordingly. Therefore, the corresponding unstable regions under different blade mounting angles are different. The large unit is generally designed with a surge alarm device for the fan. The principle is that the peak points of the performance curves corresponding to the angles of the moving blades or the stationary blades are smoothly connected to form the fan surge boundary line (as shown in the figure above), and then the surge boundary line is moved to the lower right by a certain distance. Get a surge alarm line. In order to ensure reliable operation of the fan, its working point must be at the lower right of the surge boundary line. Once the working point at a certain angle moves to the surge alarm line along the curve to the upper left due to the change of the pipeline resistance characteristic or other reasons, an alarm signal is issued to alert the operator to move the working point back to the stable zone. 

The wind pressure of the parallel fans is equal. Therefore, the fan blade with small load has a small opening degree, and the peak value of the performance curve (K point) is lower than that of the other fan. The lower the load, the more the K point is lower. Therefore, the working point of the fan with low load is likely to fall within the surge zone. Therefore, when adjusting the load of the fan, the load of the two parallel fans should not be too large to prevent the low-load fan from entering the unstable surge zone. During operation, the smoke duct is not smooth or the inlet and outlet baffles of the air volume system are incorrectly closed or incorrect. The system resistance increases, which will cause the fan to work in the surge zone. If the fan blade opening degree of the parallel fan is inconsistent or does not match the indication and the local control, the self-control failure will cause the fan characteristics to change, which will also cause the fan to surge. Fans should be avoided for long periods of time at low loads.

The above is the reason why Xiaobian has popularized about the axial fan surge. Remember, the next one will talk about the reasons for the axial fan to catch the wind.

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