7 Dynamic Similitude
262
ence much the energy rise in the through-flow with backward inclined or backward
curved blades (there is large influence with forward curved blades: see Fig. 3.19 in
Chap. 3).
7.2.6 Power Specific Speed
The internal power (rotor power) is the product of mass flow rate and rotor work.
Thus, specific speed may also be written as
i
5/ 4
m
P
.
( E )
W
D
r
Fig. 7.8 Change of shape of performance characteristics of pumps with change of specific speed;
head H, power P, efficiency η
Fig. 7.9 Circulating flows with operation at very low net flow rate in mixed flow and axial pumps.
(Adapted from [9])