Impulse turbine efficiencies: identify mechanical efficiency definition Select the correct definition of mechanical efficiency for an impulse turbine. Assume 'energy imparted to the wheel' refers to power at the runner (work done on the wheel). Choose the correct option.
Mechanical Engineering
Hydraulic Machines
Difficulty: Easy
Choose an option
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AActual turbine power ÷ energy actually supplied by the turbine (from head)
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BActual work available at the turbine shaft ÷ energy imparted to the wheel (runner power)
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CWork done on the wheel ÷ energy of the jet at inlet
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DNone of the above
Answer
Correct Answer: Actual work available at the turbine shaft ÷ energy imparted to the wheel (runner power)
Explanation
ConceptMechanical efficiency ηm accounts for mechanical (frictional) losses between runner and shaft: ηm = Shaft power / Runner power.
Option mapping(a) is overall efficiency (shaft power ÷ hydraulic power from head).(b) matches ηm.(c) is hydraulic efficiency (runner power ÷ jet power).
Final AnswerActual work available at the turbine shaft ÷ energy imparted to the wheel (runner power).