USCG Exam PracticeDiesel engine principles (motor propulsion)
In a two-stroke diesel engine, what is the primary purpose of the scavenging process?
- A. To raise the compression ratio above that achievable in a four-stroke engine
- ✓ To force fresh air into the cylinder and sweep out combustion productsCorrect
- C. To meter the quantity of fuel delivered to each cylinder
- D. To cool the exhaust valves by circulating fresh air across the valve seats
Why B is correct
Because a two-stroke engine has no separate intake or exhaust stroke, a blower or turbocharger must force fresh air in at a pressure above exhaust-manifold pressure to displace combustion products — a process called scavenging. (DOE-HDBK-1018 Vol.1 §1-2)
Cited:DOE-HDBK-1018 Vol.1 §1-2