Two-stroke engine process terminology The expulsion of burnt gases from the cylinder by the incoming fresh charge from the crankcase is called:

Introduction / Context:
In two-stroke engines, intake and exhaust processes overlap. Proper terminology distinguishes critical processes that affect power, emissions, and efficiency. This question targets recognition of the process by which exhaust gases are displaced by the fresh charge.

Given Data / Assumptions:

• A crankcase-scavenged two-stroke engine.
• Transfer ports feed fresh mixture while exhaust ports release burnt gases.
• No valves; port timing controls gas exchange.

Concept / Approach:
Scavenging is the process of sweeping out exhaust gases by the fresh charge. The quality of scavenging determines residuals, temperature, and next-cycle filling. Different scavenging methods include cross-flow, loop, and uniflow. Terms like priming, cleaning, and detonation refer to other concepts and are not correct here.

Step-by-Step Solution:
Identify the described action: burnt gases being pushed out by fresh charge.Recall the textbook term for this displacement: scavenging.Choose the term matching the definition: scavenging.

Verification / Alternative check:
Engine cycle diagrams show transfer port opening shortly after exhaust port opening, with fresh charge flow patterns designed for efficient scavenging.

Why Other Options Are Wrong:
Cleaning is a generic word, not the technical process. Priming refers to preparation of fuel or pumps. Detonation is abnormal combustion in spark-ignition engines, unrelated to gas exchange.

Common Pitfalls:
Confusing scavenging with supercharging; assuming four-stroke valve overlap is the same as two-stroke scavenging.

Final Answer:
scavenging