USCG Exam PracticeDiesel engine principles (motor propulsion)
A two-stroke diesel requires scavenging because it lacks dedicated intake and exhaust strokes. Which scavenging arrangement is described as the most efficient?
- A. Loop scavenging, where intake and exhaust ports are on the same side of the cylinder
- B. Cross scavenging, where intake and exhaust ports are on opposing sides of the cylinder
- ✓ Uniflow scavenging, with intake ports at the bottom of the liner and exhaust valves in the headCorrect
- D. Reverse-flow scavenging, where exhaust ports are at the bottom and intake valves are in the head
Why C is correct
Uniflow scavenging is the most efficient because the fresh charge enters through ports near the bottom of the cylinder and exhaust exits through poppet valves in the head, so the charge moves in one direction and displaces combustion products cleanly without mixing.
Cited:DOE-HDBK-1018 Vol.1 §1-2