How To View The Performance Curve And Efficiency Curve Of A Water Pump
Sep 21, 2024
The performance parameters of a water pump indicate its performance. But each performance parameter is not isolated or static, but interdependent and mutually restrictive. For specific water pumps, this constraint has a certain regularity. The variation pattern between them is usually represented by a curve, which is called the pump performance curve. The performance curve of a water pump is drawn through experimental methods, also known as experimental performance curve. Usually, the speed n of the water pump is taken as a constant, and the relationship between the head H, shaft power P, efficiency η, and the allowable vacuum suction height H, or the required cavitation head (NPSH) r as a function of flow rate Q is plotted as Q-H Q-p,,Q-η,Q-H, Or Q - (NPSH), curve.
It is extremely important to fully understand the performance of the water pump, be familiar with the characteristics of the performance curve, and master its variation rules for rational selection and matching, correct determination of the installation height of the water pump, adjustment of the operating conditions of the water pump, and strengthening the scientific management of the pump station.
1, Q-H pump performance curve
The Q-H curve is a decreasing curve, where the head gradually decreases with increasing flow rate. The parameters corresponding to the efficiency point of the water pump are the data listed on the water pump nameplate. Within a certain range around this point, it belongs to the high-efficiency section. In the pump sample or instruction manual, two vertical waveform lines are used to mark it, which is called the pump rate section, also known as the pump zone.
The Q-H curve of a centrifugal pump decreases relatively smoothly, and the head is highest when Q is zero. When the flow rate is zero, the head is at its maximum value, approximately twice the rated head.
2, O-P pump performance curve
The Q-P curve of a centrifugal pump is an upward curve, indicating that the shaft power increases with the increase of flow rate. When the flow rate is zero, the shaft power is at its minimum, approximately 30% of the design shaft power. The Q-P curve of an axial flow pump is a decreasing curve, meaning that the shaft power decreases with increasing flow rate. When the flow rate is zero, the shaft power is at its maximum. In the low flow area, the Q-P curve also shows a turning point.
3, Q - η Pump Performance Curve
The trend of the Q - η curve is decreasing from the maximum point to both sides.
4, Q-H, or Q - (NPSH), pump performance curve
Q-H or Q - (NPSH) are two curves that represent the suction performance of a water pump, but their variation patterns are different. The former is a decreasing curve; The latter is the curve with the minimum value at the corresponding rate point for axial flow pumps.