You are serving as a Chief Engineer (DDE)...

Question 1 / 2066636eef28f7522a1c52022e

Question 1 of 2066636eef28f7522a1c52022e

You are serving as a Chief Engineer (DDE) onboard an OSV equipped with main propulsion diesel engines of the type represented by the polar timing diagram shown in the illustration. What description best describes the engine type? Illustration MO-0084

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🔍 Key Concepts

• Study the crank angle coverage of the diagram (from TDC back to TDC) and decide whether it represents one revolution (360°) or two revolutions (720°) for a full operating cycle. • Look at the arcs showing intake and exhaust valve open periods and focus on whether there is valve overlap around TDC and how long the valves stay open. • Consider how turbocharged diesel engines typically use longer valve overlap and scavenging compared to naturally aspirated engines, and how that would appear on a timing diagram.

💭 Think About

• From the diagram, how many distinct strokes (intake, compression, power, exhaust) can you identify between one TDC and the next? What does that tell you about 2‑stroke vs 4‑stroke? • Compare the size and position of the intake and exhaust arcs: do they suggest forced scavenging with overlap, or shorter, more separated events more typical of naturally aspirated engines? • Look closely at where fuel injection begins relative to TDC—does this pattern better match common 2‑stroke marine diesels or 4‑stroke high‑speed OSV propulsion diesels?

✅ Before You Answer

• Confirm whether the full cycle in the diagram is completed in 360° or 720° of crankshaft rotation—this is the key to distinguishing 2‑stroke vs 4‑stroke. • Check for significant valve overlap around TDC; extended overlap is a strong indicator of turbocharged rather than naturally aspirated operation. • Verify which colored arc represents fuel injection and ensure its timing (start and duration) is consistent with the stroke type you’ve decided on.

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Question 1 of 20

Naturally aspirated, 4-stroke cycle engine.

Turbocharged, 2-stroke cycle engine.

Turbocharged, 4-stroke cycle engine.

Naturally aspirated, 2-stroke cycle engine.

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Question 1 / 2066636eef28f7522a1c52022e

Question 1 of 2066636eef28f7522a1c52022e

Back

Question 1 of 20

66636eef28f7522a1c52022e

No comments yet

Be the first to share your thoughts!

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🔍 Key Concepts

💭 Think About

✅ Before You Answer

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