Performance parameters of centrifugal pumps

[Mengjuan Zhu]

The main performance parameters of the centrifugal pump as follows:

1.    Flow

Flow is also called displacement, the amount of water raised. It is the amount of liquid discharged by the pump in the unit time, has two representation , one is volume units and the other is weight units.

Q expression for volume flow, the unit is m³/s, m³/h, and L/s.

G expression for weight flow, the unit is T/h, Kg/s.

The relationship between the weight flow and volume flow is G=γ Q （γ=liquid weight, kg/m³）

2.    Head

Unit weight liquid through the pump after the energy is commonly known as the lift, also known as the total head or full lift. Expressed in H, the unit is m

For high-pressure pumps, sometimes also approximately with the pump outlet and the inlet pressure difference (P2-P1 ) to indicate the head size, at this time the lift of the expression is H=104(P2-P1)/γ

P2 —outlet pressure of pump (kg/cm2)

P1 —inlet pressure of the pump(kg/cm2)

3.    Speed

The rotational speed of the centrifugal pump refers to the number of revolutions per minute of the shaft, expressed in n, the unit is r/min.

4.    Power

The power of the centrifugal pump refers to the axial power of the centrifugal pump, that is, the original motive to the pump power, expressed in N, the unit is kw.

The product of the pump's weight flow and head is called the effective power of the pump. Expressed in Ne, the unit is kg*m/s. The expression is

                Ne=GH=γQH

 The difference between shaft power N and effective power Ne of centrifugal pump is the loss of power in the pump, its size can be measured by efficiency. The efficiency of the centrifugal pump is the ratio between the effective power Ne and the shaft power N, expressed in η,

               η=Ne/N

5.    Specific speed