What is the function of regenerator?

Question

Examoogle · Accepted Answer

Option B: It heats the compressed air

Explanation & Concepts:
A regenerator is a heat exchanger used in gas turbine power plants to recover thermal energy from exhaust gases. It functions by transferring heat from the hot exhaust gas stream to the compressed air before it enters the combustion chamber.

Working Principle: In a Brayton cycle, compressed air from the compressor is initially at a lower temperature. The regenerator uses the high-temperature exhaust gas (which would otherwise be wasted) to preheat this compressed air, thereby reducing the amount of fuel required in the combustion chamber to reach the turbine inlet temperature. This process significantly improves the overall thermal efficiency of the plant.

Key Formulas: $\epsilon = \frac{T_{actual} - T_{inlet}}{T_{max} - T_{inlet}}$ — Effectiveness of a regenerator; $\eta_{thermal} = 1 - \frac{Q_{out}}{Q_{in}}$ — Thermal efficiency of the cycle

Key Points: Regeneration decreases the specific fuel consumption of the turbine.; It requires an additional heat exchanger, which increases system weight and pressure drop.; The effectiveness of the regenerator depends on the temperature difference between the turbine exhaust and the compressor discharge.

Advantages: Increases thermal efficiency of the power plant; Reduces fuel consumption for a given power output

Disadvantages: Increases initial capital cost due to heat exchanger components; Introduces pressure losses in the cycle flow paths

Applications: Gas turbine power plants; Aircraft engines (turboprop applications); Industrial heat recovery systems

Additional Info: The regenerator is most effective in plants with a low pressure ratio.. Option A is incorrect because compression is the function of the compressor, not the regenerator.. Options C and D are incorrect as a regenerator does not synthesize fuel; it merely recovers heat energy.

Answer: B is correct — The function of a regenerator is to heat the compressed air using exhaust gases to improve the thermal efficiency of the power cycle.

Exam Tip: Always remember that regeneration in power cycles is essentially a heat recovery mechanism—it saves fuel by reclaiming heat that would otherwise be exhausted into the atmosphere.

Examoogle · Answer

Option A: Eatery compresses the exhaust gases

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Option C: It regenerates the combustible gas from exhaust gas

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Option D: It regenerates the combustible oil from exhaust gas

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