Regeneration in gas turbine: What is it, Diagram, Working, TS diagram, Efficiency [with Pdf]

What is regeneration in gas turbine?

  • Regeneration in gas turbines is the recycling process in which heat energy loss with exhaust gases from the turbine is utilized to heat the air after compression.
  • The hot gases exhausted by the turbine have high heat energy therefore by using this method we save the loss of heat energy by utilizing it.
  • In this method, Regenerator is installed which is one of the heat exchangers that helps to transfer the heat of exhaust gases to air after compression and before the heat in the combustion chamber.
  • The advantage of implementing this method is that less heat supply is required to heat the air in the combustion chamber hence less amount of fuel is required.

Diagram:

Regeneration in gas turbine
regeneration-in-gas-turbine

Working of Regeneration in gas turbine:

1) When the compressor takes the air from the atmosphere and compresses it to the high temperature and pressure.

2) then after the compressor, the regenerator adds the heat of turbine exhaust gases to compressed air.

3) The air from the regenerator further flows to the combustion chamber where fuel directly mixes with the high pressure preheated air. The high-pressure hot gases come out from the regenerator which is further strikes the turbine.

4) When these high-pressure hot gases are strikes onto the turbine, where they gets to expand and work obtains at turbine output. The power developed by the turbine is also utilized to drive the compressor and for that, both compressor and turbines are connected.

5) After passes through the turbine these hot gases pass through the regenerator where their heat energy is transferred to the fresh compressed air.

In such a way, the cycle continues.

T-S diagram:

regeneration in gas turbine ts diagram
regeneration-in-gas-turbine-ts-diagram

Processes:

  • 1-2 :- Isentropic compression
  • 2-3 :- Constant pressure heat addition
  • 3-4 :- Constant pressure heat addition
  • 4-5 :- Isentropic expansion
  • 5-1 :- Constant pressure heat rejection

Efficiency calculation:

Work developed by Turbine = `W_{\text{Turbine}}= mC_{p}(T_4-T_5)`

Work to drive compressor = `W_{\text{Compressor}}= mC_{p}(T_2-T_1)` 

Heat supplied = `Q_{s}= mC_{p}(T_4-T_3)` 

Hence, efficiency (`eta`) is given by,

`= frac{mC_{p}(T_4-T_5)-mC_{p}(T_2-T_1)}{mC_{p}(T_4-T_3)}`

As `T_5= T_3`

Therefore,

Efficiency of theoretical regeneration cycle is by,

`eta = 1-frac{(T_2-T_1)}{(T_4-T_3)}`

FAQ’s:

  1. What does the regenerative system on a gas turbine do?

    Heat energy loss with exhaust gases from the turbine is utilized to heat the fresh air after compression.

  2. Why is regeneration used in gas turbine power plant?

    By using the regeneration method, Heat energy loss with exhaust gases from a turbine is utilized to heat the fresh air after compression. Resulting in increasing efficiency of the plant.

  3. What is regeneration cycle?

    The regeneration cycle is a process in which heat energy loss with exhaust gases from the turbine is utilized to heat the fresh air after compression.

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