Steam engine indicator: compute expansion ratio from cut-off A double-acting steam engine has cylinder diameter 190 mm, stroke 300 mm, and cut-off at 0.35 of the stroke. Assuming negligible clearance, determine the expansion ratio. Choose the nearest value.
Mechanical Engineering
Steam Boilers and Engines
Difficulty: Easy
Choose an option
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A1.05
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B2.86
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C6.65
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D10.05
Answer
Correct Answer: 2.86
Explanation
Given
- Cut-off fraction of the stroke, c = 0.35.
- Clearance volume is neglected (standard classroom assumption unless stated).
Concept
Expansion ratio r is the ratio of the volume at the end of the expansion to the volume at cut-off. With negligible clearance, r ≈ 1 / c.Step-by-step calculationr = 1 / c= 1 / 0.35≈ 2.857 ≈ 2.86
NoteThe cylinder diameter and stroke details are not needed once cut-off fraction is given and clearance is neglected.