Closed Cycle Gas Turbine: Construction, Working, diagram

A closed cycle gas turbine is a turbine in which the air is
circulated continuously within the turbine. The components of this turbine are compressor,
heating chamber, gas turbine which drives the generator and compressor, and a
cooling chamber.

Closed Cycle Gas Turbine

The main components of a simplest form of a closed cycle gas
turbine are:
1. Compressor: It is used to compress the gas.
2. Heating chamber: The heating of the compressed gas is takes
place in the heating chamber.
3. Gas turbine: it is used to produce the useful work which is
used by the generator to generate electricity.
4. Generator: It generates the electricity with the help of the
gas turbine.
5. Cooling chamber: Cooling of the gas after passing from the
turbine takes place in the cooling chamber.

Schematic diagram of a closed cycle gas turbine

Closed Cycle Gas Turbine: Construction, Working, diagram


  • The closed cycle gas turbine works on the principle of Joule’s
    or Brayton’s cycle
  • In this turbine, the gas is compressed isentropically and
    then passed into the heating chamber. The compressor generally used is of
    rotary type.
  • The compressed air is heated with the help of some external
    source and then made to flow over the turbine blades. The turbine used here is
    of reaction type.
  • The gas while flowing over the blades of the turbine, gets
    expanded. From the turbine the gas is passed to the cooling chamber. Here the
    gas is cooled at constant pressure with the help of circulating water to its
    original temperature.
  • Now the gas is again made to flow through the compressor to
    repeat the process.
  • Here the same gas is circulated again and again in the
    working of a closed cycle gas turbine.

P-V and T-S diagram

Closed Cycle Gas Turbine (P-V and T-S Diagram)

The various processes used in this turbine are:

1. Process 1-2: It denotes the heating of gas in heating
chamber at constant pressure.
2. Process 2-3: In this process the expansion of gas takes
place isentropically.
3. Process 3-4: This process shows the cooling of gas at
constant pressure in cooling chamber.
4. Process 4-1: Isentropic compression of gas takes place in
the compressor.

Explanation of the P-V and T-S diagram

  • Process 1-2:The heating of the gas is done at
    constant pressure. Here as the pressure is constant, so P1 = P2
    and the temperature increases from T1 to T2, the entropy
    of the gas increases during this process.
  • Process 2-3: isentropic expansion of the gas takes place in
    the turbine. Here the pressure drops from P­2 to P3 and
    volume increases from V2 to V3. In T-S diagram the
    entropy remains constant but the temperature drops from T3 to T4.
  • Process 3-4: Cooling of gas is happen at constant pressure
    during this process. In P-V diagram the pressure remain constant i.e. P3
    = P4 and the volume decreases from V­3 to V4.
  • Process 4-1: Isentropic compression takes place in the
    compressor. In P-V diagram the pressure increases from P­4 to P1
    and volume decreases from V4 to V1 (i.e. gas returns to
    its initial volume). In T-S diagram the entropy remains constant (i.e. S4
    = S1) and the temperature increases from T­4 to T1(
    T1 is the initial temperature of the gas, it means the gas attains
    its initial temperature).
Work Done (Closed cycle gas turbine)
In the above expression cp is taken in kJ/kg k
This is all about the closed cycle gas turbine. If you find
anything missing or incorrect then please don’t forget to comment.

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