Question

What data is required to generate a pump curve (head versus flow rate and pump efficiency versus flow rate) at different speeds ofa centrifugal pump?

Answer 1

Pump Performance Curve Pump performance characteristics are first analyzed independently of the rest of hydraulic system and then as a part of the system. Both sets of data are valuable to the designer. Analyzing the pump by itself gives an indication of its capabilities and performance based on the speed of rotation, internal geometry, cost factors, etc., whereas analyzing pump performance in system essentially determines pump system compatibility. In the first case, the system designer may observe performance curves to see if a specific pump has the pressure and volume flow rate to operate a given set of actuators. In a second instance, the system designer may be computing the noise, vibration, cavitation and flow characteristics of a specific pump before or after installation to determine if the pump and existing system are compatible. Where the two are necessarily complimentary, in practice much of hands-on work is completed independently. Pump performance characteristics are interpreted from data in tabular form and then graphed. Figure below shows a graphical representation of a typical positive displacement pump. Figure (a) represents the relationship between input power and pump output flow of a variable displacement piston pump as a function of pump speed.Observe the linear relationship between the discharge flow and pump speed. Figure (b) gives curves of overall and volumetric efficiencies as a function of speed. Performance curves of radial piston pump are given in Fig (c). Discharge flow of these pumps is nearly constant over a broad pressure range.Discharge flow can be varied infinitely between the point of inflection on the constant discharge portion of the curve and zero flow

(a)