Gas Turbine Power Plant

Ambient air is drawn in and cleaned in the inlet filter house.

Ambient air enters through a filter house with weather hoods, pre-filters and HEPA/EPA final stages. Every millibar of inlet pressure drop costs output, so filter ΔP is a daily reading. Air density decides capacity — the same machine loses roughly 0.5–0.9 % power per °C rise in ambient temperature, which is why evaporative coolers, foggers or inlet chillers are fitted in hot climates.

Axial compressor raises the air to 15–30 bar and 350–450 °C.

The axial compressor — typically 14 to 18 stages of rotating blades and stationary vanes — squeezes the air to 15–30 bar and 350–450 °C. Variable inlet guide vanes control airflow during start-up, part load and combined-cycle exhaust temperature control, and protect the machine from surge. Fouling of the blade surfaces is the single most common cause of silent output and efficiency loss.

Fuel gas is injected and burned in the combustors at 1100–1500 °C.

Fuel gas at 25–45 bar, filtered, heated above its dew point and metered by the gas control valves, is burned in annular or can-annular combustors. Dry Low NOx burners pre-mix fuel and air to hold flame temperature down and keep NOx below 25 ppm without water or steam injection. Firing temperature of 1100–1500 °C is possible only because the first-stage parts are film-cooled and coated with thermal barrier ceramics.

Hot gas expands through the turbine — two-thirds of the power drives the compressor.

The hot gas expands through the turbine stages. Roughly two-thirds of the power developed is consumed internally by the compressor on the same shaft — the remaining one-third is the useful output. This is why gas turbine performance is so sensitive: a small drop in compressor efficiency eats directly into net output, several times over.

Exhaust at 500–600 °C leaves via the stack — or feeds an HRSG in combined cycle.

Exhaust leaves at 500–600 °C. In simple cycle it goes up the stack through a silencer and the plant sits around 32–42 % efficiency. In combined cycle it feeds a multi-pressure HRSG that raises steam for a steam turbine, lifting plant efficiency to 55–62 %; in cogeneration the same heat makes process steam, chilled water via absorption chillers, or hot water.

Generator output is stepped up by the GSU transformer to the grid.

The generator, cooled by air or hydrogen and excited through a static or brushless exciter, delivers power at 11–15 kV. The generator step-up transformer raises this to the grid voltage, with synchronising, protection relays, and the DCS/turbine control system governing speed, load, temperature limits and the full sequence of start, load, unload and cooldown.