Oilers/Plant Tenders (HHC) Civil Service Practice Exam

In a 2-stroke cycle diesel engine, what is scavenged into the cylinder?

1. Exhaust gases

2. Combustion air

3. Fuel mist

4. Oil vapor

The correct answer is: Combustion air

In a 2-stroke cycle diesel engine, combustion air is scavenged into the cylinder to facilitate the combustion process. The operation of a 2-stroke diesel engine involves the intake and exhaust processes happening simultaneously, where the air enters the cylinder during the scavenging phase, replacing the exhaust gases that are expelled. This influx of fresh air is crucial as it helps maintain efficient combustion, allowing for the complete burning of the fuel that will be injected into the cylinder afterward. Unlike a 4-stroke engine that relies on separate intake and exhaust strokes, a 2-stroke engine uses the movement of the piston to achieve both intake (scavenging) and exhaust within the same cycle. Therefore, fresh combustion air is necessary to ensure optimal performance and power output from the engine. This understanding is central to the operation of 2-stroke engines and highlights the critical role of scavenging air in the overall process.