1. What is the characteristic curve of the pump?
The curve representing the relationship between the main performance parameters is usually called the performance curve or characteristic curve of the centrifugal pump. In essence, the performance curve of the centrifugal pump is the external manifestation of the movement law of the liquid in the pump and is obtained through actual measurement. The characteristic curves include: flow-head curve (QH), flow-efficiency curve (Q-η), flow-power curve (QN), flow-cavitation surplus curve (Q- (NPSH) r), and the function of the performance curve is At any flow point of the pump, a set of relative head, power, efficiency and cavitation margin values can be found on the curve. This group of parameters is called the working state, referred to as the working condition or working point, centrifugal pump The working condition of the highest efficiency point is called the best working condition point, and the best working condition point is generally the design working condition point. Generally, the rated parameters of the centrifugal pump, that is, the design operating point and the optimal operating point coincide or are very close. It is important to know the performance parameters of the pump to run in the selected efficiency interval in practice, that is, to save energy and to ensure the normal operation of the pump.
2. What is the efficiency of the pump? What is the formula?
Refers to the ratio of the effective power of the pump to the shaft power. η = Pe / P
The power of the pump usually refers to the input power, that is, the power transferred from the prime mover to the pump shaft, so it is also called the shaft power, and is represented by P.
The effective power is: the product of the pump's head and mass flow and gravity acceleration.
Pe = ρg QH (W) or Pe = γQH / 1000 (KW)
ρ: Density of liquid transported by pump (kg / m3)
γ: the gravity of the liquid transported by the pump γ = ρg (N / m3)
g: acceleration of gravity (m / s)
Mass flow Qm = ρQ (t / h or kg / s)
