What percentage of the air is generally used to support combustion in a turbine engine?

In turbine engines, the percentage of air that supports combustion is typically in the range of 20-25%. This is due to the need for a precise fuel-to-air ratio for efficient combustion. In most turbine engines, a substantial amount of the incoming air is bypassed around the combustion chamber—this air is referred to as bypass air, and it contributes to the overall thrust of the engine but does not participate in the combustion process.

The percentage of air used for combustion is crucial because it affects engine performance and efficiency. Operating within the 20-25% range allows the engine to maintain optimal combustion temperatures while ensuring that the combustion process is efficient enough to deliver the required thrust without producing excessive emissions or requiring more fuel than necessary. Additionally, this range aligns with typical designs of modern turbofan engines, where a balance between power output and fuel efficiency is essential for operational viability.

Other percentages suggested in the remaining choices either overestimate or underestimate the typical operational parameters for turbine engines, as they include too much of the bypass or would not provide sufficient airflow for effective combustion, impacting performance.