FAA Powerplant Written Practice Test

What is the primary purpose of the diffuser section of a turbine engine?

1. To decrease air temperature

2. To increase air pressure and decrease velocity

3. To support combustion

4. To accelerate air flow

The correct answer is: To increase air pressure and decrease velocity

The primary purpose of the diffuser section of a turbine engine is to increase air pressure and decrease velocity. As air flows through the diffuser, its cross-sectional area expands, which leads to a reduction in the velocity of the air. According to Bernoulli's principle, as the velocity of air decreases, its pressure increases. This process is crucial because it prepares the air for efficient combustion in the combustor section of the engine. The increased pressure helps ensure that the air mixes appropriately with fuel, leading to a more efficient combustion process, which ultimately enhances engine performance. While other options may describe various aspects of turbine engine operation, they do not accurately capture the essential function of the diffuser in transitioning the airflow condition from the high-speed compressor to the combustion chamber.