FAA Powerplant Written Practice Test

Where are the highest heat to metal contacts found in a jet engine?

1. Compressor inlet

2. Turbine inlet nozzle vanes

3. Exhaust section

4. Combustion chamber walls

The correct answer is: Turbine inlet nozzle vanes

The highest heat to metal contacts in a jet engine occur in the turbine inlet nozzle vanes. This area is subject to extreme temperatures due to the combustion of fuel and air, which reaches its peak once the combustion process has completed and the hot gases enter the turbine section. The temperature of the gases at this point can exceed 1,500 degrees Fahrenheit or more, posing significant challenges to the materials used in manufacturing the turbine components. The nozzle vanes are specifically designed to withstand these intense thermal conditions, as they direct the high-temperature gases onto the turbine blades with optimal efficiency. In contrast, while the combustion chamber walls do experience high temperatures, the direct contact between the extremely hot gases and the metal is more pronounced in the turbine inlet nozzle area, where the heat transfer is critical for the performance and efficiency of the turbine. Additionally, components like the compressor inlet and the exhaust section experience lower thermal stresses compared to the turbine inlet nozzle vanes, reinforcing the idea that the turbine inlet nozzle is where the most significant heat to metal contacts occur.