3.1.10 Axial pump curve

Axial pump curve

In the case of pumps of the axial or semi-axial type, different performances according to the axial pump curve can be obtained through alteration of the angular position of the blade on the impeller, figure 3.20. In approximately the same way the performance is altered by adjusting guide vanes on the inlet side of such pumps figure 3.110a.

Pump curves for an axial pump with adjustable impeller blades. The curves a-e designate different settings. The performance is expressed relative to the design point (ηmax)

Pump curves for semi-axial pump With adjustable guide vanes on the inlet side. The angular values relate to the angle setting of the guide vanes.

If the pump speed is altered then a different performance is obtained which is also expressed as a series of curves in the Q-H and the Q-P diagrams. An existing pump curve with Q-H and Q-P diagrams is recalculated from, for example, a maximum speed to some other speed by recalculating 4-5 points on the maximum curves one after the other to the new speed With the help of the affinity laws and the transmission efficiencies for the actual speed converter. Figure 3.22 shows an example of such recalculated pump performances. A more detailed treatment of speed regulated pumps recurs in Chapter 8.