ABSTRACT
Fig. 10.21 shows the typical performance curves for a Pelton wheel.
It will be noted that the curves are approximately parabolic in shape, thus conforming to theory; also that the optimum efficiency occurs at approximately 50 per cent of no load or runaway condition. The cor responding curves for a representative Francis turbine (Fig. 10.22) exhibit a much greater falling off in efficiency either side of the optimum. This is because there is shock loss at entry. Iso-efficiency curves may be drawn in a similar manner to those for pumps.
