What is the Brayton cycle?

• A. thermodynamic cycle of gas turbine engine to produce thrust
• B. thermodynamic cycle of turbojet engine to convert heat to electricity
• C. A cycle in piston engines
• D. A cycle describing rocket propulsion

Answer: (A)

The Brayton cycle describes how a gas turbine engine operates. It involves four stages: compressing incoming air, adding heat at essentially constant pressure in the combustor, expanding the hot gases through a turbine to drive the compressor, and then exhausting through a nozzle to produce thrust. In a turbojet, the fuel is burned to raise the gas temperature and pressure; the turbine extracts some energy to drive the compressor, and the remaining energy leaves the engine as high-speed exhaust that generates thrust. This cycle is specific to gas turbine propulsion and is not how piston engines (which follow Otto or Diesel cycles) or rocket propulsion work. It’s also not about converting heat to electricity in a turbojet—the thrust-producing Brayton cycle is the focus in gas turbine propulsion.