- Gas Turbine Power Plant Definition: A gas turbine power plant is a complex system that converts the energy from burning fuel into mechanical and then electrical energy.
- Main Components: The essential parts include a compressor, regenerator, combustion chamber, gas turbine, alternator, and starting motor.
- Compression and Heating: Air is first compressed in the compressor, then heated in the regenerator using waste heat from the turbine, optimizing energy use.
- Energy Transformation: In the combustion chamber, fuel burns to drastically increase air temperature for efficient energy transfer to the turbine.
- Electricity Production: The alternator, connected to the turbine, generates electricity as the turbine rotates, utilizing the mechanical energy produced by the gas turbine.
The schematic of a gas turbine power plant follows the Brayton cycle: a compressor, a combustor and a turbine on one or more shafts, plus a generator. This drawing also shows a regenerator and a starting motor. The main parts labelled here are the
- compressor,
- regenerator,
- combustion chamber,
- gas turbine,
- alternator, and
- starting motor.
Compressor
A power-station gas turbine usually uses an axial compressor. Inlet filters take dust out of the air. Rotating blades and stationary vanes raise the air pressure in many stages. Small machines may use a centrifugal compressor instead.
Regenerator
A regenerator, or recuperator, is a heat exchanger on some gas turbine power plant layouts. Exhaust gas heats the compressor discharge air before that air reaches the combustor. Many large simple-cycle and combined-cycle plants omit this unit and send exhaust to a chimney or a heat-recovery steam generator instead.
Combustion Chamber
Compressed air, with or without a regenerator, enters the combustion chamber. Fuel, often natural gas or distillate oil, burns in a fraction of that air. Flame temperature can be far above the blade limit. Dilution air then mixes the gas down to the turbine inlet temperature. Older notes quote about 3000°F then 1500°F to 1300°F. The US DOE describes gas as hot as about 2300°F in typical plant turbines, with advanced inlet temperatures higher still.
Alternator
On a single-shaft set the alternator rotor is coupled to the turbine shaft. As the turbine turns, the alternator sends electrical energy to the grid. Aero-derivative plants may use more than one shaft.
Starting Motor
In a single-shaft gas turbine power plant the compressor, turbine and often the alternator share one shaft. The compressor cannot deliver firing air until it is already spinning, so a starter turns the shaft. The starter may be an electric motor, a diesel or the generator run as a motor from a static frequency converter.
Turbine
Hot gas enters the turbine through nozzles or stator vanes and expands through the stages. The drop is staged. Shaft work comes from both impulse and reaction stages on a modern machine. Older notes give an exhaust temperature near 900oF. Simple-cycle exhaust is often about 450 to 600°C, depending on the design.
