Engineering
A gas turbine is an internal combustion engine that converts the chemical energy of fuel into mechanical work through a continuous flow of compressed, combusted gases. It operates on the Brayton cycle, comprising compression, combustion, and expansion stages. Gas turbines are widely used for power generation, aviation propulsion, marine propulsion, and industrial mechanical drive applications.
The gas turbine operates on the Brayton cycle, a thermodynamic cycle in which air is compressed adiabatically, heated at constant pressure in a combustor, and then expanded adiabatically through a turbine. The core components are the compressor, combustor, and turbine, arranged in a single continuous flow path. In a typical configuration, the compressor raises the air pressure by a factor of 10 to 30, fuel is injected and burned, and the hot gases expand through the turbine, which drives both the compressor and an external load such as an electrical generator or propeller.
The turbine section is the most thermally stressed part; advanced engines use single-crystal superalloy blades with internal cooling channels and thermal barrier coatings to withstand inlet temperatures above 1,500 °C. The efficiency of the cycle improves with higher pressure ratios and turbine inlet temperatures, but material limits and cooling losses impose practical constraints.
Gas turbines are used in a wide range of settings. In aviation, they power jet engines, turboprops, and turboshafts, where their high power-to-weight ratio is essential. In power generation, they are used for peaking plants, combined-cycle plants (where exhaust heat generates steam for a steam turbine), and cogeneration. Industrial gas turbines also drive natural gas compressors on pipelines and pumps in oil and gas facilities.
Marine applications include naval frigates, cruise ships, and fast ferries, where compactness and rapid start-up are valued. Aero-derivative gas turbines, adapted from aircraft engines, offer high flexibility and quick load changes, while heavy-frame machines are optimized for base-load efficiency. Combined-cycle plants can achieve efficiencies above 60%, making them among the most efficient thermal power plants.
The concept of a continuous combustion turbine dates to the 1791 patent of John Barber, but the first practical gas turbine was built in 1903 by Ægidius Elling in Norway, which produced net positive power. Early development was slow due to material limitations. In 1930, Frank Whittle patented a turbojet engine, and Hans von Ohain independently developed a working jet engine in Germany, leading to the first jet-powered flight in 1939.
Post-war, gas turbines entered power generation and marine propulsion. The 1960s saw the introduction of high-temperature alloys and air cooling, enabling higher efficiencies. The 1990s brought advanced H-class machines with steam-cooled blades. Today, research focuses on hydrogen combustion, additive manufacturing of components, and digital twin monitoring.
Beyond mainstream uses, gas turbines have niche applications. They are used in some high-speed trains, such as the French TGV prototype, and in military main battle tanks like the M1 Abrams, which uses a Honeywell AGT1500 turbine. Gas turbines also power some natural gas pumping stations and are used in small-scale distributed generation, including microturbines (25–500 kW) for combined heat and power.
An overlooked historical figure is Aurel Stodola, whose early 20th-century thermodynamic analyses laid the groundwork for turbine design. Another edge case is the use of gas turbines in lunar or Martian rovers, where they could operate on methane and oxygen. The first gas turbine power plant in the US was at the Sun Oil refinery in Marcus Hook, Pennsylvania, in 1949, using a Westinghouse turbine.
Gas turbines are a cornerstone of modern power and propulsion, with ongoing innovations in materials and fuels.
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