Skip to main content

Gas turbine engine components and arrangement

Short answer

Main components: compressor raises air pressure; combustion chamber burns fuel at constant pressure; turbine expands hot gases to produce work. In open-cycle, air is drawn from and exhausted to atmosphere; closed-cycle recirculates a clean working fluid through an external heater and cooler, allowing higher pressures and any fuel source but is bulkier and costlier.

Draw the schematic diagram of a simple open-cycle gas turbine plant and explain the function of each component. Differentiate between open and closed cycle gas turbine plants.

Schematic of the open-cycle gas turbine

                    fuel
                     |
          +---+      v      +-----------+      +---+
 air ---->| C |------------>| Combustor |----->| T |----> exhaust
          +-+-+             +-----------+      +-+-+
            |                                    |
            +-------------- shaft ---------------+----> load

Functions

  1. Compressor (C): axial or centrifugal; raises the pressure of the air from atmospheric to p2p_2 (pressure ratio 6 to 30). It absorbs 50 to 60% of the turbine work.
  2. Combustion chamber: fuel is burnt at nearly constant pressure with only part of the air (primary air); the rest dilutes and cools the gases to the turbine limit (about 1100 to 1500 K).
  3. Turbine (T): the gases expand to atmospheric pressure and develop work. Part of it drives the compressor; the remainder is the net output.
  4. Starting motor, fuel pump, lubricating system and other auxiliaries.

Open and closed cycle

PointOpen cycleClosed cycle
Working fluidAir drawn from and exhausted to the atmosphereThe same gas (air, helium) circulates repeatedly
HeatingInternal combustion in the chamberExternal heater (heat exchanger)
CoolingExhaust to the atmosphereA cooler brings the gas back to the compressor inlet state
FuelClean liquid or gaseous fuel onlyAny fuel, even coal or nuclear heat
Pressure levelAtmospheric at the inletCan be raised, giving smaller machines
Size, costCompact, cheapLarger and costly (heat exchangers)
Blade foulingPossible with dust and ashNone, clean working fluid
UseAircraft, power plants, peak loadSpecial plants, nuclear and solar

The open cycle is far more common because of its simplicity, light weight and quick start.

✓ Answer checked by Claude Opus 5.5 (high effort)

Related questions

All Turbo Machines chapter 3 questions →