FAA Powerplant Written Practice Test

What primarily causes turbine engine emissions?

1. Lack of maintenance

2. High combustion temperatures

3. Type of fuel used

4. Exhaust system design

The correct answer is: High combustion temperatures

High combustion temperatures are the primary cause of turbine engine emissions. In turbine engines, the combustion process occurs at elevated temperatures and pressures, which leads to the formation of nitrogen oxides (NOx), a significant component of engine emissions. When the combustion temperature exceeds a certain threshold, the nitrogen in the air combines with oxygen to form NOx, which is a byproduct of high-temperature combustion processes. The design of the combustion chamber and the combustion efficiency also play a role in how effectively fuel is burnt and, consequently, how much emissions are produced. However, even with optimal design and maintenance, increased combustion temperatures inherently lead to a higher formation of pollutants like NOx. Thus, controlling the combustion temperature is crucial in managing and reducing those emissions, particularly in turbine engines where this relationship is particularly pronounced.