The power available at the shaft of a Francis turbine is 1 MW. The volume flow rate of water in 25 m3/s, whirl velocity at inlet is 10 m/s and blade velocity is 5 m/s. Find the mechanical efficiency (in %)?

Correct Answer: 80
Mechanical efficiency is given by ηm = shaft power / ρQVw1u1. Substituting the given values into this equation, we get mechanical efficiency = 80%.