FAA Powerplant Written Practice Test

How does the temperature of air affect the performance of the turbine engine?

1. Cooler air increases engine efficiency

2. Warmer air decreases combustion efficiency

3. Air temperature does not affect performance

4. Cooler air requires more fuel

The correct answer is: Cooler air increases engine efficiency

The performance of a turbine engine is significantly impacted by air temperature, with cooler air playing a key role in enhancing engine efficiency. Cooler air is denser, which means that it contains more molecules in a given volume. When this denser air enters the engine, it allows for a greater mass flow of oxygen, which can improve combustion efficiency. This results in more power being produced from the same amount of fuel, thereby increasing overall engine performance and efficiency. In addition to improving combustion, cooler air also helps to optimize various thermodynamic processes within the engine, such as the Brayton cycle, which is crucial for jet engine operation. As the air cools, the density increases while the energy required for compression and combustion stays relatively constant, thereby enhancing the specific thrust produced by the engine. This relationship illustrates why engine performance is directly linked to air temperature, making cooler air preferable for achieving maximum efficiency in turbine engines.