Ideal cycle for a closed-cycle gas turbine A closed-cycle gas turbine (with external heat addition and rejection, using a working gas in a loop) ideally operates on which thermodynamic cycle?

Introduction / Context:
Gas turbines—open or closed—are conceptually based on the Brayton (Joule) cycle, consisting of isentropic compression, constant-pressure heat addition, isentropic expansion, and constant-pressure heat rejection. The “closed” qualifier refers to how heat is added/removed and whether the working fluid is recirculated, not to the underlying cycle type.

Given Data / Assumptions:

• Closed loop with a working gas (often helium, nitrogen, or air).
• External heater and cooler provide constant-pressure heat transfer.
• Ideal turbomachinery with isentropic compression/expansion.

Concept / Approach:
The hallmark of the Brayton (Joule) cycle is constant-pressure heat transfer. In a closed-cycle implementation, the same gas recirculates through compressor, heater, turbine, and cooler. Regeneration is frequently added in practice to improve thermal efficiency, but the base ideal cycle remains Brayton.

Step-by-Step Solution:

Verification / Alternative check:
Ericsson and Stirling cycles involve isothermal processes; Rankine is a vapor cycle for steam plants; Carnot is an ideal limit with isothermal and adiabatic processes, not the practical gas-turbine basis.

Why Other Options Are Wrong:

Constant-pressure heating/cooling distinguishes Brayton from Ericsson/Stirling; Rankine applies to phase-change (liquid-vapor) cycles; Carnot is not used directly due to impractical isothermal compression/expansion.

Common Pitfalls:
Equating “closed cycle” with non-Brayton cycles; closure is about recirculation, not changing the fundamental thermodynamic processes.

Final Answer:

Joule (Brayton) cycle