The Brayton cycle is known as the constant ... cycle.

The Brayton cycle is known as the constant ... cycle.

• A. Constant Volume Cycle
• B. Constant Pressure Cycle
• C. Isothermal Cycle
• D. Adiabatic Cycle

Answer: (B)

The main idea being tested is that the Brayton cycle operates with heat addition and heat rejection at roughly constant pressure. In a gas turbine, air is compressed to a high pressure, then fuel is burned in the combustor. The burning raises the gas temperature, but the pressure stays nearly the same because the downstream flow is matched to the compressor discharge. The hot gas then expands through the turbine, doing work, and exits at about the same pressure as it entered. In the ideal Brayton model, the cycle includes two constant-pressure heat-transfer steps (during combustion and during exhaust) flanked by two adiabatic (isentropic) steps of compression and expansion. This constant-pressure behavior distinguishes it from cycles that assume heat addition at constant volume, constant temperature, or no heat transfer at all.

The main idea being tested is that the Brayton cycle operates with heat addition and heat rejection at roughly constant pressure. In a gas turbine, air is compressed to a high pressure, then fuel is burned in the combustor. The burning raises the gas temperature, but the pressure stays nearly the same because the downstream flow is matched to the compressor discharge. The hot gas then expands through the turbine, doing work, and exits at about the same pressure as it entered. In the ideal Brayton model, the cycle includes two constant-pressure heat-transfer steps (during combustion and during exhaust) flanked by two adiabatic (isentropic) steps of compression and expansion. This constant-pressure behavior distinguishes it from cycles that assume heat addition at constant volume, constant temperature, or no heat transfer at all.