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 low in the liner and exhaust valves in the headCorrect
- D. Reverse scavenging, where exhaust enters at the bottom and fresh air exits at the top
Why C is correct
DOE-HDBK-1018 Vol.1 §1-2 identifies uniflow scavenging — intake ports near the bottom of the liner uncovered by the piston skirt, exhaust poppet valves in the head — as the most efficient because the fresh charge moves in one direction and displaces exhaust cleanly.
Cited:DOE-HDBK-1018 Vol.1 §1-2