Gas turbine, cut open

Air path

• Inlet filter houseCleans and quiets a river of air before the compressor.+

  A turbine this size swallows several hundred kilograms of air every second. The filter house strips dust and salt, a silencer cuts noise, and optional evaporative coolers or chillers cool the air on hot days to recover power.

  Airflow

  ≈600–1,000 kg/s

  Filtration

  Multi-stage, up to EPA/HEPA (E12)

  Pressure drop

  ≈0.5–1 kPa

  Options

  Inlet chilling or fogging, anti-icing

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• Axial compressorRows of spinning blades squeeze air about 20 times.+

  Alternating rows of rotating blades and fixed vanes each raise pressure a little. Variable inlet guide vanes at the front adjust airflow for part load. The compressor absorbs roughly half of the power the turbine makes.

  Stages

  ≈14–21

  Pressure ratio

  ≈20–24 : 1

  Exit temperature

  ≈450–500 °C

  Speed

  3,600 rpm (60 Hz, direct drive)

  Power absorbed

  ≈50% of turbine output

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Hot section

• Combustion systemA ring of cans where natural gas burns in compressed air.+

  Compressed air and fuel mix in a ring of combustor cans. Dry low-NOx designs premix lean so the flame stays cooler and makes less nitrogen oxide. Newer units can burn hydrogen blends.

  Layout

  Can-annular, ≈12–16 cans

  Firing temperature

  ≈1,400–1,600 °C

  NOx

  ≈9–25 ppm (DLN), lower with SCR

  Fuel

  Natural gas; ≈30–50% H₂ blends offered

  Fuel flow

  ≈15–20 kg/s at full load

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• Turbine sectionHot gas spins four stages of superalloy blades.+

  The hot gas expands through four stages, spinning the shaft. First-stage blades run in gas hotter than their own melting point, survived only by internal air cooling channels, film cooling holes and ceramic thermal-barrier coatings.

  Stages

  4

  Blade material

  Single-crystal nickel superalloy

  Coatings

  Ceramic thermal barrier (YSZ)

  Cooling

  Internal passages + film holes

  Inspection

  Hot gas path ≈every 24,000–32,000 h

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• Exhaust diffuser and stackStill about 600 °C, carrying roughly 60% of the fuel energy out.+

  The diffuser slows the exhaust to recover pressure. In simple cycle it leaves through a stack; in combined cycle a heat recovery steam generator turns that heat into steam for a second turbine, lifting efficiency from about 43% to over 63%.

  Exhaust temperature

  ≈600–650 °C

  Simple-cycle efficiency

  ≈41–44% (LHV)

  Combined-cycle efficiency

  ≈63–64% (LHV)

  Stack height

  ≈20–40 m

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Generator and grid

• Rotor and bearingsOne solid shaft from compressor to turbine to generator.+

  A bolted stack of forged discs forms a single rotor weighing on the order of 100 tonnes, riding on oil-film journal bearings and a thrust bearing that holds it in place axially.

  Speed

  3,600 rpm

  Rotor mass

  ≈80–120 t

  Bearings

  Tilting-pad journal + thrust

  Monitoring

  Vibration, temperature, axial position

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• GeneratorTurns shaft power into 60 Hz electricity at about 20 kV.+

  A two-pole synchronous generator spins with the turbine at grid frequency. Large units are hydrogen-cooled because hydrogen carries heat far better than air with less drag.

  Output

  ≈300–550 MW (H-class simple cycle)

  Voltage

  ≈18–24 kV

  Cooling

  Hydrogen (large units) or air

  Efficiency

  ≈98.8–99%

  Start

  Static frequency converter spins it up

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• Generator step-up transformerLifts ≈20 kV to transmission voltage.+

  Connects the generator through isolated-phase bus to the grid or straight to a campus substation. At a behind-the-meter AI campus this may step to 34.5 kV for site distribution instead.

  Rating

  ≈350–600 MVA

  Ratio

  ≈20 kV → 230–500 kV (or 34.5 kV on site)

  Cooling

  ONAN/ONAF/ODAF

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Auxiliaries

• Fuel gas skidFilters, heats and meters gas to the right pressure.+

  Pipeline gas is filtered, heated to stay above its dew point and controlled through stop and control valves. H-class units need high fuel pressure, often requiring a compressor at the site.

  Supply pressure

  ≈3–4.5 MPa (≈450–650 psig)

  Flow

  ≈2–3 million m³ per day at full load

  Safety

  Double block-and-bleed valves

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• Lube oil systemKeeps every bearing floating on a film of oil.+

  A reservoir, pumps, coolers and filters feed oil to every bearing. An emergency DC pump keeps oil flowing while the rotor coasts down if all AC power is lost.

  Reservoir

  ≈15,000–30,000 L

  Pumps

  AC main, AC standby, DC emergency

  Turning gear

  Rotates the shaft slowly while cooling

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• Control and starting packageBrains, fire protection and the starting system.+

  The control system manages start, load and protection. A static starter runs the generator as a motor to bring the shaft up to speed; the unit can reach full load in about 10–30 minutes. A CO₂ system protects the enclosure.

  Start to full load

  ≈10–30 min (aeroderivatives ≈5–10)

  Ramp rate

  ≈50–90 MW/min

  Fire protection

  CO₂ or water mist in enclosure

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