Main factors influence centrifugal pump performance
1. Liquid physical properties influence to characteristic curves
Factory provided characteristic curve is using clean water as working medium measure, when conveying other liquids, need to consider the influence of liquid density and viscosity.
(1) Viscosity when conveying liquids viscosity is larger than experimental conditions water viscosity, pump body energy loss increases, the flow, pressure head decreases, and efficiency decreases, the shaft power increased.
(2) density centrifugal pump volume flow and pressure head is nothing to do with liquid density, power increases with density increases.
2. rotating speed influence to characteristic curve
When the liquid viscosity is not big, the efficiency unchanged, pump flow, pressure head, shaft power and rotate speed can be approximately calculated by proportion law, namely:
In formula, Q1, H1, N1 centrifugal pump rotating speed is the n1 flow, head and power.
Q2, H2, N2 centrifugal pump rotate speed is N2 flow, head and power.
The aboved group formula called proportion law. When rotate speed change less than 20%, can consider efficiency is changeless, using aboved formula to calculate error is small.
If choose more points in rotate speed n1 performance curves, using proportion law calculates speed n2 corresponded data, and write the result in the coordinate plot on paper, then can get the speed n2 characteristic curve.
3. impeller diameter influence to characteristic curve
When the pump rotate speed is certain, its head, flow is related to impeller diameter.
In formula, Q1, H1, N1 centrifugal pump rotate speed is D1 flow and head and power.
Q2, H2, N2 centrifugal pump rotate speed is D2 flow and head and power.
