FAA Powerplant Written Practice Test

What are the most important factors that affect thermal efficiency in a turbine engine?

1. Fuel type and engine age

2. Turbine inlet temperature, compression ratio, and component efficiencies

3. Cylinder configuration and fuel mixture

4. Oil viscosity and ambient temperature

The correct answer is: Turbine inlet temperature, compression ratio, and component efficiencies

The most important factors affecting thermal efficiency in a turbine engine are turbine inlet temperature, compression ratio, and component efficiencies. Turbine inlet temperature is a critical determinant of thermal efficiency; higher temperatures generally lead to improved efficiency because the engine can extract more work from the hot gases. However, this is limited by material constraints and cooling technology, which must effectively manage and withstand these elevated temperatures. The compression ratio also plays a significant role in thermal efficiency. A higher compression ratio allows for a greater amount of energy extracted from the expansion of combustion gases, thus improving overall efficiency. This means that more energy from the fuel's combustion is converted into useful work rather than being lost as waste heat. Component efficiencies, including the efficiencies of the compressor, combustor, and turbine, further influence the overall thermal efficiency of the engine. Higher efficiencies in these components mean that less energy is lost to friction, heat, and other losses, allowing for more efficient energy conversion and utilization in the engine. While factors such as fuel type and engine age can have an impact, they are not as directly related to the fundamental thermodynamic processes that determine efficiency within the engine compared to the parameters mentioned above. Similarly, factors like cylinder configuration and oil viscosity do not significantly affect thermal efficiency in