The affinity laws for speed change work for all rotodynamic pumps (radial, axial and mixed flow impellers) but for impeller diameter change the laws only apply for radial flow impellers - can anyone tell me why this is the case?
This is interesting - more so that the first set of equations hold for speed but not necessarily for dia changes yet so many publications (including some text books i have trawled up) seem to refer to them and only a few refer to the second set
further comment?
OK cheers for that,
Can anyone tell me why the second set of equations are not just used in all circumstances.
I plotted the pump curve using both sets of equations and there is very little difference, until the flows are higher, for small impeller diameter changes since D1/D2 is close to 1, so...
Thanks for that,
So in essence what you are saying is that the first set of equations are only applied for trimming (or increasing)the impeller diameter within the same sized volute and the second set should be applied when the volute size is changed within a family of like pumps?
Hi,
I have come accross an interesting problem when looking to change impeller diameter to increase the flow output of a centrifugal pump.
Some books quote using the affinity laws:
Q1/Q2 = (D1/D2)
H1/H2 = (D1/D2)^2
P1/P2 = (D1/D2)^3
to redraw a...
