Starting of a centrifugal blower
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According to the instructions, when starting the blower, the outlet should be opened first, followed by the inlet gradually. Why is it necessary to do this? Can’t you open the entrance first when starting up? I don’t quite understand; please explain, it will earn extra points
The operation of centrifugal fans is the opposite of that of centrifugal pumps, as centrifugal fans are used to transport air or gases, while centrifugal pumps are used to transport liquids. In the case of centrifugal fans, the process of transportation relies on the centrifugal force exerted by the impeller to compress the air within the casing; the outlet is opened first while the inlet remains closed, so that the fan does not start under high load. Once the outlet is opened and the inlet is closed, the fan compresses only the limited amount of air inside the casing, resulting in the lowest compression ratio and thus the lowest load. If the inlet is opened while the outlet remains closed, air will continue to flow into the casing and be compressed by the centrifugal force of the impeller. Since the outlet is not open, a large amount of air gets compressed, and at a certain point the fan will experience surge, leading to vibrations in the casing and resonance, which can damage the seals and the balance of the impeller. This is my understanding; I hope experts can provide further guidance.
This is related to the compressibility coefficient of the fluid; additionally, there are the startup conditions prior to starting up the equipment, which are two different concepts from the operational procedures after it has been started. Special note.