USCG Exam PracticeDiesel engine principles (motor propulsion)
In a two-stroke diesel engine, uniflow scavenging is considered the most efficient scavenging arrangement. What distinguishes uniflow scavenging from other arrangements?
- A. Intake and exhaust both occur through ports in the cylinder wall at the same level
- ✓ Intake ports are located low in the liner and exhaust leaves through poppet valves in the head, so the fresh charge moves in one directionCorrect
- C. A Roots-type blower forces exhaust out through opposing ports while the piston is at top dead center
- D. Exhaust ports are located low in the liner and intake air enters through valves in the head
Why B is correct
DOE-HDBK-1018 Vol.1 §1-2 defines uniflow scavenging as having intake ports low in the liner uncovered by the piston skirt and exhaust poppet valves in the head, so the fresh charge sweeps through in one direction and displaces combustion products cleanly, making it the most efficient arrangement.
Cited:DOE-HDBK-1018 Vol.1 §1-2