Gas Turbine
Overview
A gas turbine is an internal combustion engine that compresses air, mixes it with fuel, combusts it, and uses the resulting high-temperature, high-pressure gas to rotate a turbine, thereby obtaining mechanical energy. It operates on the same principle as a jet engine and is widely used for power generation, aviation, and industrial applications. Advantages include high power density and rapid start-up, while challenges include low part-load efficiency and durability issues of high-temperature components.
Main Content
Operating Principle
Gas turbines are based on the Brayton cycle. Air is compressed to high pressure in a compressor, mixed with fuel, and combusted in a combustor. The high-temperature, high-pressure combustion gas expands as it passes through the turbine, generating rotational force. The exhaust gas from the turbine can be used for additional power or directed to a heat recovery system to produce steam in combined-cycle power generation.
Main Components
- Compressor: Axial or centrifugal type compresses air 10 to 30 times. Multi-stage design improves efficiency.
- Combustor: Burns fuel (natural gas, diesel, hydrogen, etc.) mixed with air; flame temperature reaches 1500–1700°C. Lean combustion technology reduces NOx emissions.
- Turbine: Core component that extracts rotational force from the expansion of hot gas. Uses single-crystal superalloys and thermal barrier coatings (TBC).
- Exhaust System: Releases exhaust gas to the atmosphere or sends it to a heat recovery steam generator (HRSG).
Types
- Medium and Large Gas Turbines: 50–600 MW class for power generation. Combined-cycle efficiency exceeds 60%. Major manufacturers include GE, Siemens, and Mitsubishi Power.
- Aviation Gas Turbines (Turbofan, Turbojet): Thrust-optimized design, evolving toward lightweight and high-temperature operation.
- Industrial Small Gas Turbines: 1–50 MW, used for combined heat and power (CHP), offshore plants, and pipeline compressor drives.
- Micro Gas Turbines: 30–300 kW, for distributed power and hybrid vehicles.
Efficiency and Performance
Simple-cycle efficiency is 30–40%, but combined-cycle (gas turbine + steam turbine) can achieve over 60%. Latest H-class and J-class turbines have turbine inlet temperatures above 1600°C and pressure ratios above 23:1. Variable inlet guide vanes (IGV) are adopted to compensate for part-load efficiency degradation.
Advantages and Disadvantages
Advantages: Fast start-up (reaches rated output within minutes), high power density, fuel flexibility (natural gas, hydrogen, biogas), low initial investment (compared to coal-fired power).
Disadvantages: Low part-load efficiency, limited lifespan of high-temperature components (requiring periodic replacement), noise and emissions (NOx, CO2) issues.
Applications
- Power Generation: Base and peak load power, complementing renewable energy variability (backup power).
- Aviation: Propulsion for commercial and military aircraft.
- Industry: Power for chemical and refinery plants, LNG liquefaction and regasification.
- Marine: Ship propulsion (COGAS, CODLAG).
- Military: Tanks (M1 Abrams AGT1500), naval vessels.
Latest Trends
From 2024 to 2025, gas turbine technology focuses on decarbonization, hydrogen combustion, and digitalization. GE, Siemens, and Mitsubishi Power are developing commercial 100% hydrogen combustion gas turbines; in 2024, GE's 7HA.03 model achieved 50% hydrogen co-firing certification. Japan plans to complete demonstration of a 1700°C-class J-class turbine by 2025. Additionally, research on ammonia co-firing and fuel cell hybrid systems is active. Digital twins and AI-based predictive maintenance improve operational efficiency, and low-carbon power solutions combined with carbon capture (CCUS) are gaining attention. In South Korea, Doosan Enerbility successfully localized a 380 MW ultra-large gas turbine (commercial operation in 2024) and is developing hydrogen co-firing technology.
Related Topics
- [[Brayton cycle]]
- [[Combined cycle power plant]]
- [[Jet engine]]
- [[Hydrogen combustion]]
- [[Thermal barrier coating]]
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