Analysis of the performance curve of the pump: The characteristic curve of the pump is measured at a certain speed, so the speed n value is marked on the characteristic graph. The horizontal coordinate mark on the performance curve of the pump indicates the flow, and the vertical coordinate indicates the lift. There is a root flow and a lift curve.
Under normal circumstances, when the lift is increased, the flow rate drops. You can check the flow according to the lift or check the flow. To the lift; there is also the root efficiency curve, which is high in the middle and low on both sides. It indicates that the flow rate and the lift are the most efficient in the middle section. Therefore, we should pay attention to the head and flow of the pump when we select the pump, which is near the highest efficiency curve; There is a power (axis power) curve that generally increases with increasing flow. Note that its shaft power should not exceed the motor power.
Curve: Q-H, flow and head curve trend graph, thick line is the recommended working range. The lift--flow curve takes the centrifugal water pump as an example. The pump performance curve includes QH (flow-lift), QN (flow-power), Qn (flow-efficiency) and Q-Hs (flow-allowed vacuum height) ).
Each flow rate Q corresponds to a certain head H, shaft power N, efficiency n and allowable vacuum height Hs. The head is reduced as the flow increases. Q-H (flow-lift) is an irregular curve. The parameter corresponding to the (Qo, Ho) point of the highest efficiency value is the data listed on the pump nameplate.
It will be one of the most economical jobs of the pump. Within a certain range around this point (generally not less than 5% of the highest efficiency point) is a highly efficient section called the high-efficiency section of the pump. When selecting the pump, the flow rate and head required for the pump station design should fall within the high efficiency range.
