🔍 Key Concepts

• Review the sequence of events in a two-stroke diesel cycle: scavenging, compression, combustion/power, and exhaust. • Understand that supercharging means air is being forced into the cylinder under pressure, usually when the scavenge ports are open. • Relate each numbered segment (I, II, III, IV) to whether the piston is near TDC or BDC and which valves/ports are open.

💭 Think About

• On a uniflow two-stroke engine, during which crank-angle range are the scavenge ports open and fresh air is flowing in from the air receiver? • How does the timing of exhaust valve opening/closing compare with the timing of the scavenge ports opening/closing on the diagram? Which arc best matches that overlap where air is being blown in? • Which segment would clearly NOT be supercharging because both inlet and exhaust are closed (i.e., true compression or expansion periods)? Eliminate those first.

✅ Before You Answer

• Identify on the illustration which segment corresponds to scavenge ports open. • Identify which segment corresponds to both ports/valves closed (pure compression or expansion) and rule those out for supercharging. • Confirm that the segment you select occurs when cylinder pressure is being raised by an external blower/turbocharger, not by piston compression alone.