Question 14.12: Hydroturbine Design A retrofit Francis radial-flow hydroturb...
Hydroturbine Design
A retrofit Francis radial-flow hydroturbine is being designed to replace an old turbine in a hydroelectric dam. The new turbine must meet the following design restrictions in order to properly couple with the existing setup: The runner inlet radius is r_{2}=8.20 ft (2.50 m ) and its outlet radius is r_{1} =5.80 ft (1.77 m ) . The runner blade widths are b_{2}=3.00 ft (0.914 m) and b_{1}=8.60 ft (2.62 m) at the inlet and outlet, respectively. The runner must rotate at \dot{n}=120 rpm (\omega=12.57 rad / s ) to turn the 60-Hz electric generator. The wicket gates turn the flow by angle \alpha_{2}=33^{\circ} from radial at the runner inlet, and the flow at the runner outlet is to have angle \alpha_{1} between -10° and 10° from radial (Fig. 14–99) for proper flow through the draft tube. The volume flow rate at design conditions is 9.50 \times 10^{6} gpm (599 m³/s), and the gross head provided by the dam is H_{\text {gross }}=303 ft (92.4 m). (a) Calculate the inlet and outlet runner blade angles \beta_{2} \text { and } \beta_{1} , respectively, and predict the power output and required net head if irreversible losses are neglected for the case with \alpha_{1}=10^{\circ} from radial (withrotation swirl). (b) Repeat the calculations for the case with \alpha_{1}=0^{\circ} from radial (no swirl). (c) Repeat the calculations for the case with \alpha_{1}=-10^{\circ} from radial (reverse swirl).
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