- 2078 Chaitra · 4 marks
Francis versus Kaplan applicability
Short answer
Francis is a mixed-flow reaction turbine for medium heads, 10–350 m, medium discharge, Ns 60–300, fixed blades and guide-vane regulation. Kaplan is axial-flow for low heads, 2–40 m, large discharge, Ns 300–1000, adjustable runner blades with double regulation, better part-load efficiency but needs deeper setting.
Differentiate applicability of Francis and Kaplan Turbine in reference to hydropower project.
Both Francis and Kaplan are reaction turbines, but the Francis is a mixed-flow turbine for medium heads, while the Kaplan is an axial-flow turbine with adjustable blades for low heads and large discharge.
| Point | Francis | Kaplan |
|---|---|---|
| Flow | Radial in, axial out (mixed) | Axial |
| Head range | About 10–350 m (typically 30–300 m) | About 2–40 m |
| Discharge | Medium | Large |
| Specific speed (kW) | 60–300 | 300–1000 |
| Runner blades | Fixed, 9–19 vanes | Adjustable, 3–8 blades |
| Regulation | Guide vanes only | Guide vanes and runner blades (double) |
| Part-load efficiency | Falls below ~40–50% load | High over wide range |
| Cavitation | Moderate | Higher; needs deep setting |
| Typical project | Medium-head ROR/PROR in hills | Barrage or canal-drop plant on large rivers |
In hydropower projects: Francis suits most medium-head schemes in Nepal's hills (e.g. Kaligandaki "A", Middle Marsyangdi). Kaplan suits low-head, high-flow sites such as barrages on large rivers in the plains, canal falls and run-of-river schemes with large and varying flow.
✓ Answer checked by Claude Opus 5.5 (high effort)
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