Gas turbines are rotary engines that convert the chemical energy of a fuel into mechanical work via a high‐speed gas flow, driving compressors, shafts, or electric generators. They operate on the Brayton (or Joule) thermodynamic cycle—comprising compression, combustion, expansion, and exhaust—to achieve continuous power output. Modern gas turbines range from simple‐cycle units with efficiencies around 30–40% to combined‐cycle installations exceeding 60%, and ongoing innovations (advanced materials, hydrogen fuel compatibility, and aerodynamic improvements) promise even greater performance and lower emissions. Below is a structured overview of their design, operation, applications, efficiency trends, and emerging developments.

Overview

Gas turbines, also known as combustion turbines, are a class of internal combustion engines in which compressed air and fuel are mixed and ignited to generate high‐velocity exhaust gases that spin turbine blades to produce work or thrust. They are a backbone of modern power generation, propulsion, and industrial drives.

Working Principle

The Brayton Cycle

Gas turbines operate on the open‐cycle Brayton (Joule) cycle:

1. Compression: Ambient air is drawn in and pressurized by the compressor.

2. Combustion: Fuel is injected into the combustor, mixing with compressed air and burning at high temperature.

3. Expansion: Hot gases expand through the turbine section, doing work on the turbine blades (which in turn drive the compressor and an output shaft).

4. Exhaust: Spent gases are expelled to the atmosphere.

Closed Brayton cycles recirculate the working fluid via a heat exchanger instead of direct combustion, useful in space power systems and certain industrial plants.

Main Components

1. Compressor: Usually an axial‐flow machine compressing incoming air to high pressures. Small industrial turbines may use centrifugal compressors for simplicity at lower pressure ratios.

2. Combustor (Burner): A series of fuel injectors and flame holders where fuel–air mixing and combustion occur, reaching temperatures over 2 000 °F (1 093 °C).

3. Turbine: High‐temperature, high‐pressure gases expand across turbine stages, driving both the compressor (via a shared shaft) and an external load (generator or propulsor).

4. Exhaust System: Directs spent gases out, which in combined‐cycle setups feed steam generators for additional power extraction.

Types of Gas Turbine Installations

• Simple‐Cycle Gas Turbine: Direct expansion to atmosphere; typical thermal efficiencies of 30–40 % Wikipedia.

• Combined‐Cycle Gas Turbine (CCGT): Waste heat from the gas turbine’s exhaust powers a steam turbine, boosting overall efficiency to 50–60 % and up to 64 % in state‐of‐the‐art plants.

• Closed‐Cycle Gas Turbine: Uses a separate heat source (e.g., nuclear reactor or external burner) with recirculated working fluid; applied in niche power and aerospace systems.

Applications

• Aviation: Gas turbines provide jet thrust in turbofan, turbojet, and turboprop engines, powering commercial, military, and private aircraft—their largest single market.

• Power Generation: Utility‐scale turbines drive generators in simple and combined cycles; flexible operation suits load following and grid support.

• Marine Propulsion: Naval vessels and high‐speed commercial ships use marine gas turbines for compactness and high power density.

• Industrial Drives: Mechanical drives for compressors, pumps, and pipelines in oil & gas, petrochemical, and manufacturing sectors.

Efficiency and Performance Trends

• Simple vs Combined: A simple‐cycle unit averages ~34 % efficiency, whereas combined‐cycle plants reach up to 64 % under optimal conditions.

• Utilization Growth: In the U.S., combined‐cycle capacity factors climbed from 40 % in 2008 to 57 % by 2022, reflecting improved competitiveness and grid integration.

• Advanced Materials & Cooling: Single‐crystal superalloys and sophisticated cooling schemes allow higher turbine inlet temperatures, raising efficiencies further.

Environmental and Future Developments

• Hydrogen Fuel Integration: Siemens Energy’s Zero Emission Hydrogen Turbine Center demonstrated operation on blends up to 15 % H₂ by volume, cutting CO₂ by ~1 ton per hour of full‐load operation.

• 100 % Hydrogen Capability: The HYFLEXPOWER consortium led by Siemens successfully tested a turbine running on pure H₂, natural gas, or any mix, paving the way for fully decarbonized power cycles.

• Carbon Capture & Storage (CCS): Integration of CCS units with gas‐turbine power plants is progressing through pilot and demonstration projects to mitigate residual CO₂ emissions.

• Renewable Integration: Gas turbines’ rapid ramp‐rate and cycling flexibility complement variable renewable sources, acting as dispatchable “firming” resources.

Conclusion

Gas turbines remain indispensable across propulsion, power generation, and industrial sectors due to their high power‐density, scalability, and improving efficiency. Advances in materials, aerodynamics, and fuels (notably hydrogen) are catalyzing a new era of cleaner, more efficient turbines, ensuring their continued role in a decarbonizing energy landscape.