USCG Exam PracticeDiesel engine principles (motor propulsion)
In a two-stroke diesel, 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 liner at bottom dead center
- ✓ 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 the intake 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
Uniflow scavenging uses intake ports uncovered by the piston skirt near bottom dead center and exhaust poppet valves in the head. Because the fresh charge travels in a single direction from bottom to top, it displaces combustion products cleanly and is the most efficient scavenging method. (DOE-HDBK-1018 Vol.1 §1-2)
Cited:DOE-HDBK-1018 Vol.1 §1-2