How many cycles are there in a gas turbine engine?

• A. 2
• B. 3
• C. 4
• D. 5

Answer: (C)

Gas turbine engines run on the Brayton cycle, which has four main stages in each operating cycle: compression, where incoming air is pressurized; combustion, where fuel is added and burned to raise the air’s energy; expansion, where the high-energy gases flow through and drive the turbine to produce shaft power; and exhaust, where the gases are expelled to atmosphere and the cycle begins again. These four processes together constitute the complete cycle, and that’s why the correct count is four. In practice, intake and exhaust are part of the cycle’s boundaries, but the four fundamental stages remain the standard way to describe the cycle.