Definition of mechanical efficiency for turbines Fill in the blank: The ratio of actual work available at the turbine shaft to the energy imparted to the wheel (runner) is called ________ efficiency. Choose the correct term.

Efficiency taxonomy

• Hydraulic efficiency = Runner power / Water power at runner inlet.
• Mechanical efficiency = Shaft power / Runner power (accounts for mechanical losses in bearings, windage, etc.).
• Overall efficiency = Shaft power / Water power at turbine inlet.

Therefore
'Actual work available at the turbine' (shaft output) divided by 'energy imparted to the wheel' (runner input) is mechanical efficiency.

Final Answer
Mechanical efficiency.