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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.

Difficulty: Easy

1.05
2.86
6.65
10.05

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 calculation
r = 1 / c= 1 / 0.35≈ 2.857 ≈ 2.86

Note
The cylinder diameter and stroke details are not needed once cut-off fraction is given and clearance is neglected.

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