I believe everyone has encountered the problem of centrifugal fan surge, so what is centrifugal fan surge? What causes the surge of the fan? How to solve it?
1) What is centrifugal fan surge
The surge of the centrifugal fan refers to the pulsation of pressure and flow when the fan is running in an unstable area, mainly manifested as a violent fluctuation in the flow, which makes the airflow have a violent impact, and the fan itself produces strong vibration and noise. The phenomenon.
The fan with hump-shaped performance curve works in large-capacity management. When the change of flow is less than the critical flow, the full pressure of the fan will drop. Because of the large capacity of the pipeline, the resistance of the pipeline does not change temporarily, and the pipeline resistance is greater than the full pressure. The fluid flows backwards, negative flow occurs, and then the pressure of the pipeline drops to 0, and the pressure reaches a lower value. As the fan continues to work, the flow is re-delivered, the pressure rises, and the process repeats. When the flow is positive and sometimes negative, the pressure fluctuates up and down, fluctuates greatly, and the phenomenon of periodic violent vibration of the fan’s pipeline is the fan surge.
2) Reasons for centrifugal fan surge
There are many reasons for fan surge, such as:
1. Fan speed: When the speed of the centrifugal fan changes, its performance curve also changes accordingly, so this method can be used to change the operating point to meet the production adjustment requirements.
2. Pipeline characteristics: The characteristics of the pipeline also have a great influence on the surge. Usually, the larger the capacity of the pipe network, the higher the amplitude of the surge, and the lower the frequency, the more serious the surge will be , the more destructive it is.
3. Other factors: For example, the opening of the inlet guide vane of the fan, the structure of the impeller; the intake state of the fan’s intake temperature, pressure, gas composition, etc., will cause the fan to surge.
Three) centrifugal fan surge solution
1. Eliminate surge
(1) Start the inverter
The fan cooperates with the frequency converter to reduce the operating frequency of the fan motor to eliminate the surge, which is effective when the blower starts, but this method actually reduces the use capacity of the fan and can only be used temporarily.
(2) Air duct deflate
A bypass pipe is set in the air outlet pipe. If the air volume is reduced to the lower limit air volume, the valve on the bypass pipe will automatically open and begin to deflate. At this time, the flow at the inlet increases, and the working point can be moved from the surge area to the stable working area. It can eliminate the possibility of stall and surge caused by small intake air flow and large angle of attack.
(3) Strengthen training
Strengthen the skill training of operators and prohibit improper operation. During the operation of the equipment, if the startup is improper, the outlet valve cannot be opened quickly, which will cause the unit to operate in a small flow state, so the correct operation is very important. To immediately open the outlet, increase the flow, and make the unit run under normal conditions to eliminate surge.
2. Prevent surge
(1) The characteristics of the pipe network are changed to avoid the blockage of the pipe network.
(2) Avoid high intake air temperature, low pressure and reduction of gas molecular weight.
(3) Pay attention to the smooth and slow opening and closing of the anti-vibration valve.
(4) Avoid too fast lifting and lowering speed in the process of starting and stopping. Pay attention to the sequence of first increasing the speed and then increasing the pressure, and first decreasing the pressure and then decreasing the speed.
(5) Regularly check the oil temperature, oil pressure, current and voltage of the fan, and the temperature rise of the main motor, etc., to ensure that the fan is in good operating condition and avoid surge.
After the above answer to the question of what is centrifugal fan surge, it can be seen that centrifugal fan surge refers to the pulsation phenomenon of pressure and flow generated in unstable areas and forms. The reasons for surge mainly include fan speed, pipeline characteristics, Other factors, etc., can eliminate the surge by starting the inverter, venting the air duct, strengthening training, etc., and in daily use, avoid blockage of the pipe network, avoid high intake air temperature and low pressure, pay attention to the operation sequence, and regularly. Check, etc., in order to prevent the occurrence of surge.