Power (expansion) stroke timing in a four-stroke diesel engine Identify the typical angular span for the expansion stroke (combustion/expansion period) in a four-stroke diesel engine. Choose the correct option.
Mechanical Engineering
IC Engines and Nuclear Power Plants
Difficulty: Medium
Choose an option
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AStarts at 15° before TDC and ends at 30° after TDC
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BStarts at TDC and ends at 30° after TDC
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CStarts at 15° after TDC and ends at 30° before BDC
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DMay start and end anywhere
Answer
Correct Answer: Starts at 15° after TDC and ends at 30° before BDC
Explanation
ConceptIn a diesel engine, fuel injection begins near TDC and continues slightly after; peak pressure follows soon after TDC. The useful expansion then proceeds until exhaust opens typically some degrees before BDC (≈ 30–50°), ending the effective expansion early.
ReasoningThus, a representative textbook span is: start ≈ few degrees after TDC, end ≈ some degrees before BDC — matching option C.
Final AnswerStarts at 15° after TDC and ends at 30° before BDC