Open-cycle gas turbine basics: Which statements correctly characterize an open-cycle gas turbine plant?

Introduction / Context:
Gas turbine plants can operate in open or closed cycles. In an open cycle, the working fluid is atmospheric air that is compressed, heated by direct fuel combustion, expanded through the turbine, and then exhausted to the atmosphere. Understanding which components are typical (and which are not) helps distinguish open-cycle layouts from closed-cycle or combined-cycle systems.

Given Data / Assumptions:

• Simple open Brayton cycle without regeneration, intercooling, or reheating (though these may be added in practice).
• Combustion takes place directly in a combustor.
• Exhaust is discharged to atmosphere; no recirculation of the same working fluid.

Concept / Approach:
Open-cycle plants avoid indirect heaters/recuperators in their simplest form (though recuperators can be added to improve efficiency). Crucially, they do not use a condenser to liquefy the working fluid; condensers are characteristic of steam Rankine cycles. Therefore, statements (a) and (b) are correct for the simple open cycle, while (c) is incorrect.

Step-by-Step Solution:

Verification / Alternative check:
Typical simple-cycle gas turbines comprise compressor, combustor, and turbine, with exhaust going to stack; no condenser is present.

Why Other Options Are Wrong:

• Individual (a) or (b) alone: Incomplete; both apply.
• A condenser is used: Not in open Brayton cycles.
• All of the above: Would erroneously include the condenser.

Common Pitfalls:
Confusing open vs closed Brayton layouts; assuming every thermal plant has a condenser because steam plants do.

Final Answer:
both (a) and (b)