Definition
In a gas turbine engine, expansion is the stage in which high-pressure, high-temperature gas from the combustion section increases in volume as it passes through the turbine and exhaust sections, giving up pressure and temperature to produce work and thrust.
Plain English
Hot, squeezed gas spreading out and pushing through the back of the engine. As it spreads, it drives the turbine wheels and exits as thrust.
Context Anchor
Seen in gas turbine engine discussions, especially when describing how compressed air and hot gases move through the engine after combustion.
Derivation
From Latin 'expandere' meaning 'to spread out.' In a turbine, the gas that was tightly compressed in the front of the engine is now allowed to spread back out as it moves rearward, and that spreading is what does the useful work.
Why Pilots Care
Expansion is where the engine actually produces power. Understanding it helps make sense of why turbine engines need both a compressor up front and a turbine in the back, and why exhaust gas temperature matters.
Grounding Statement
Picture hot, squeezed air being released into more space; as it spreads out, it can push on parts inside the engine and help create thrust.
Intuition Check
Expansion does not just mean “getting bigger” in a general way here. In this engine context, it means gas spreading into more space as pressure energy is turned into engine work and thrust.
Example Sentence 1
During expansion, the hot gas drives the turbine wheels before exiting through the exhaust.
Example Sentence 2
Efficient expansion in the low-pressure turbine contributes to overall engine thrust.