Hydraulic efficiency of Francis turbine whose vanes are radial at inlet is (α – guide blade angle)
1
\(\frac{{2 + {{\tan }^2}\alpha }}{2}\)
2
\(\frac{{{{\tan }^2}\alpha }}{2}\)
3
\(\frac{2}{{2 + {{\tan }^2}\alpha }}\)
4
\(\frac{2}{{ta{n^2}\alpha }}\)
5
Question Not Attempted