Gas turbine heat recovery: does adding a regenerator (recuperator) increase the thermal efficiency of a basic Brayton cycle?

Introduction / Context:
A regenerator (recuperator) transfers heat from the hot turbine exhaust to the compressed air before combustion. This reduces the fuel required to achieve a given turbine inlet temperature, improving thermal efficiency in many Brayton-cycle applications.

Given Data / Assumptions:

• Simple gas turbine (compressor–combustor–turbine) augmented with a regenerator.
• Moderate pressure ratio and non-ideal component efficiencies.
• Exhaust temperature above compressor exit temperature so that heat exchange is possible.

Concept / Approach:
Thermal efficiency = net work output / heat supplied. With regeneration, part of the required heat input is supplied internally by exhaust energy. If the temperature of turbine exhaust exceeds the compressor outlet temperature, effective fuel heat input decreases for the same net work, increasing efficiency.

Step-by-Step Solution:
Baseline: determine T_comp_out and T_turb_out without regeneration.If T_turb_out > T_comp_out, add a regenerator to preheat compressed air.Combustor fuel input drops to reach target turbine inlet temperature.Net work remains similar; heat supplied decreases → efficiency rises.

Verification / Alternative check:
T–s or h–s diagrams with a regenerator show reduced external heat addition area for the same cycle work rectangle/loop.

Why Other Options Are Wrong:

• “Incorrect”: contradicts Brayton analysis under typical conditions.
• Other conditional choices are irrelevant or physically inconsistent.

Common Pitfalls:
At very high pressure ratios, T_comp_out can approach or exceed T_turb_out, limiting regenerator effectiveness; the statement remains broadly correct for suitable ratios.

Final Answer:
Correct