Methods for adjusting the air volume and pressure of centrifugal fans.
1. Adjustment of inlet and outlet valves
The adjustment of the outlet valve of the centrifugal fan will increase the resistance of the pipe network and change the characteristics of the pipe network. Therefore, the pressure drop is consumed on the additional resistance generated when the air valve is closed. For such an adjustment, the economy is not good. When the exhaust duct is placed on the suction side of the fan, the working principle of adjusting the air inlet valve is the same as that of the air outlet valve. The method of changing the fan performance curve by changing the air inlet of the fan is more economical.
2. Snail line setting
This method mainly changes the characteristics of the fan by changing the outlet area of the centrifugal fan. Compared with the reduction of air volume, the fan power does not change much, and the energy saving effect is not obvious. This adjustment method is applicable to all working conditions below the rated curve, and can change the surge point in the direction of small flow. Therefore, it is widely used in fans with fixed speed.
3. Adjust the impeller blade size
By changing the size of the centrifugal fan blades, the air flow direction of the inlet impeller is changed, thereby changing the performance curve of the fan. By adjusting the air volume at the fan inlet, all operating conditions below the performance curve can be achieved when the inlet guide vane angle is zero; adjusting the air volume can increase the total pressure and air volume of the fan, but the adjustment range is limited. This adjustment method is very cheap and is widely used today.
