Gas Turbines — Working Cycle of an Open-Cycle Plant An open-cycle gas turbine (typical jet engine or simple-cycle gas turbine) ideally operates on which thermodynamic cycle?

Introduction / Context:
Open-cycle gas turbines draw in fresh air, compress it, add heat by combustion at essentially constant pressure, expand the hot gas through a turbine, and exhaust to the atmosphere. The idealized model for this is the Joule (Brayton) cycle.

Given Data / Assumptions:

• Air-standard assumptions with constant specific heats.
• Two isentropic (compression, expansion) and two isobaric (heat addition, rejection) processes.
• Open cycle: intake and exhaust occur to the surroundings.

Concept / Approach:
The Joule (Brayton) cycle consists of: isentropic compression (compressor), constant-pressure heat addition (combustor), isentropic expansion (turbine), and constant-pressure heat rejection (exhaust). It captures the essential physics of open-cycle gas turbines better than Carnot, Otto, or Stirling cycles.

Step-by-Step Solution:
Match components to ideal processes: compressor ⇒ isentropic compression; combustor ⇒ isobaric heat addition.Turbine ⇒ isentropic expansion; exhaust/recuperator (if absent) ⇒ isobaric rejection to ambient.Therefore, the correct ideal cycle is the Joule (Brayton) cycle.

Verification / Alternative check:
TS and PV diagrams for Brayton align with measured compressor/turbine maps and constant-pressure combustors, confirming the idealization.

Why Other Options Are Wrong:
Carnot is an ideal limit with isothermals/adiabats; Otto uses constant-volume heat addition; Stirling uses isothermal plus constant-volume regeneration—none matches gas-turbine hardware.

Common Pitfalls:
Confusing Brayton with Otto due to “spark-ignition vs. turbine” contexts; assuming Carnot applies as a practical cycle template.

Final Answer:
Joule's cycle