Regarding centrifugal fans and Roots fans? Urgent! Urgent! Urgent! ! !

When the inlet is narrowed, the power and current certainly decrease. Head is a property of the equipment and is unrelated to the valve; what is measured during actual operation is the outlet pressure, not head. The outlet pressure will decrease.

Fans do not have a head value; instead, they have an ultimate pressure value. Head refers to pumps. If you close the inlet valve, the load on the fan decreases; with a reduced load, the current also necessarily decreases. Looking at efficiency again, it will definitely decrease. If you completely close off the inlet, the fan will no longer be able to perform useful work, but it will still consume electricity. At this point, the efficiency has dropped to 0. The maximum pressure that a Roots blower can generate is determined by the clearance of the blower’s impellers and the material’s tolerance. The pressure at the fan outlet is determined by the resistance in the pipeline ahead of it. If the pipeline ahead is closed, the outlet pressure will keep increasing until the safety valve activates; if there is no resistance in the pipeline ahead, the fan outlet pressure cannot rise and remains very low

Fans do not have a head value; instead, they have an ultimate pressure value. Head refers to pumps. If you close the inlet valve, the load on the fan decreases. May I ask, does this also apply to positive-displacement fans? Is the current also decreasing? I asked the teacher: why does the current increase when the volume-type valve is closed? Very puzzled?

When starting a positive displacement fan, the inlet valve should not be fully open, but it also shouldn’t be fully closed either; if it is fully closed, it functions like a vacuum pump, and the current actually increases. It is recommended to open the valve to 30 degrees first at the time of startup, then increase the opening angle after startup, or ensure that the inlet valve is not kept fully closed for too long.

Ask why it’s not set to full on