How is the centrifugal pump flow, head, shaft power, efficiency changing?

Centrifugal pump operating point is determined by the characteristics of the pump curve and the pipe characteristic curve: characteristic pump curve H = Ho - SoQ ^ 2 is a descending curve concave to the characteristics, pipe


curve H = Z2-Z1 + SQ ^ 2 is a concave curve upward increment.


H- pump head, Ho - Pump head when flow is zero, So-- pump friction, Q- pump flow,


Z1- pump sump water level, Z2-- out of the pool water level, S- - pipe friction.


Changes in the degree of opening of the centrifugal pump outlet valve means the pipeline characteristic curve changes.

When the valve opening becomes smaller, the line resistance increases (S increases).

When the pipeline characteristic curve steepens, the intersection of the pump characteristic curves move to flow smaller, bigger lift direction.

When the valve opening becomes large, the opposite. As for shaft power, efficiency is determined by the change in pump and piping characteristic curve characteristic curve. For the pump, the shaft power with the smaller valve opening becomes smaller.