Impulse turbine efficiencies: identify mechanical efficiency definition Select the correct definition of <strong>mechanical efficiency</strong> 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).