Actual operating conditions for centrifugal pump impeller cutting
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The impeller changes in size (i.e., diameter) as a result of cutting, and the most significant change is in the head; the head decreases. The reason is that energy is transferred from the impeller to the medium, that is, to the water. If the water leaves the impeller quickly, it means no more energy is being transferred to the medium; as a result, its potential energy becomes very low, and consequently the pumping head of the water pump decreases. That’s the simple explanation for this phenomenon. However, according to the performance curve of the water pump, the head decreases and the flow rate will change, increasing slightly as a result. Is this statement correct?
I’m hearing for the first time that the flow rate increases when using an impeller cut; I’m not sure about other pumps, but I’ve definitely never encountered such a situation with centrifugal pumps
Your statement is not entirely correct; after the impeller is cut, the flow rate, head, and power all decrease accordingly. The flow rate cannot increase. When the diameter of the impeller is reduced, the linear velocity of the circular motion also decreases. Based on the relationship between velocity and pressure energy, the pressure as well decreases. As the flow velocity decreases, the flow rate also decreases. (Flow rate refers to the amount of fluid – whether liquid or gas – that passes through a certain surface per unit of time, measured in terms of volume or mass.) If you don’t understand, just communicate. Regarding ordinary centrifugal pumps. Hope this helps!
That’s absolutely correct. The original poster said that the flow rate would change depending on the performance curve of the pump, but I’m not sure if the poster has actually seen what that curve looks like. In fact, the curve is quite clear: each time the impeller cuts through the fluid, both the flow rate and the head decrease. I know this is the case for centrifugal pumps; please correct me if there’s anything incorrect in what I’ve said
For the same impeller, when the head decreases, the flow rate generally increases. However, the impeller after cutting is no longer the original one; its performance curve has changed, so it cannot be compared with the previous one.
I never even thought of such a premise; impressive!
After cutting the same impeller, the flow rate remains unchanged while the head decreases.
Treat centrifuges with caution. Cutting the impeller is not that simple. Also, this formulaic relationship is similar to that of resistance, current, and voltage. If I keep the voltage constant and the current decreases, does that mean the resistance increases? Obviously not. It’s not this causal relationship.
The pump performance curve should be determined through testing (it may not be accurate; I hope experts can help answer this question). The performance curve can change even after replacing components (our factory replaced the impeller, and the pump’s performance improved significantly), not to mention when the impeller is cut. If the pump outlet flow is too high or the pressure is too high, it is recommended to increase the recirculation flow; cutting the impeller is not advised.