What is a gas turbine engine?

A gas turbine engine is a type of continuous flow internal combustion engine. It operates on a thermodynamic cycle, typically the Brayton cycle, where air is compressed, fuel is added and ignited, and the resulting hot gases expand through a turbine to produce power.

What are the fundamental components common to all gas turbine engines?

The core components of a gas turbine engine, in order of airflow, are a rotating gas compressor, a combustor, and a compressor-driving turbine. An air inlet is also essential.

How does a gas turbine engine function according to the Brayton cycle?

In an ideal Brayton cycle, atmospheric air is compressed to a higher pressure, energy is added through combustion at constant pressure, the high-temperature gas expands through a turbine to produce shaft work (used to drive the compressor), and the exhaust gases are expelled. The cycle is an open system, meaning the air is not reused.

What are some common applications for gas turbine engines?

Gas turbines are used to power aircraft, trains, ships, electric generators, pumps, gas compressors, and tanks. They are versatile machines found in many industrial and transportation sectors.

Who is credited with patenting the first true gas turbine, and what was its intended purpose?

John Barber, an Englishman, was granted a patent in 1791 for the first true gas turbine. This invention was designed to power a horseless carriage.

What significant achievement did Ægidius Elling accomplish in 1903 regarding gas turbines?

In 1903, Ægidius Elling, a Norwegian, built the first gas turbine that produced more power than was needed to run its own components. This engine, using rotary compressors and turbines, generated 8 kW (11 hp).

When did Frank Whittle patent his design for a gas turbine for jet propulsion, and when did it first successfully run?

Frank Whittle patented his design for a centrifugal gas turbine for jet propulsion in 1930. The first successful test run of his engine occurred in England in April 1937.

What was the significance of the Junkers Jumo 004 engine in 1944?

The Junkers Jumo 004 engine entered full production in 1944, powering the first German military jets like the Messerschmitt Me 262. This marked the beginning of the widespread use of gas turbines for aircraft propulsion.

What is the primary purpose of a turboprop engine?

A turboprop engine is designed to drive an aircraft propeller. It uses a reduction gear to match the high rotational speed of the turbine section to the lower speeds required for efficient propeller operation.

How do turbofan engines differ from turbojets?

Turbofan engines, unlike turbojets, produce thrust not only from the exhaust gases but also from a ducted fan driven by the turbine. This fan moves a larger volume of air (bypass air), significantly improving fuel efficiency and reducing noise compared to turbojets.

What are aeroderivative gas turbines, and where are they commonly used?

Aeroderivative gas turbines are typically based on existing aircraft gas turbine engines. They are generally smaller and lighter than industrial gas turbines and are often used in electrical power generation and the marine industry due to their quick response times and lower weight.

What is a key challenge in designing turbine blades for high-temperature gas turbines, and how is it addressed?

A major challenge is reducing creep, which is deformation caused by high temperatures and stresses. This is addressed through methods like high-performance coatings and the use of single-crystal superalloys, which improve the material's resistance to deformation.

How do thermal barrier coatings (TBCs) help protect turbine blades?

TBCs, often made of stabilized zirconium dioxide ceramics, provide thermal insulation to the blade. By limiting the temperature exposure of the underlying superalloy, they reduce the rate of creep and other high-temperature degradation mechanisms.

What is the primary advantage of gas turbine engines for aircraft propulsion?

The primary advantage is their high power-to-weight ratio. This means they can generate significant power from a relatively lightweight engine, making them ideal for aircraft where weight is a critical factor.

What are microturbines, and what are their typical efficiencies?

Microturbines are small gas turbines, typically ranging from 25 to 500 kilowatts, often the size of a refrigerator. Their efficiencies are around 15% without a recuperator, 20-30% with one, and can reach up to 85% combined thermal-electrical efficiency in cogeneration applications.

What is an 'externally fired gas turbine' (EFGT)?

An EFGT is a type of gas turbine where the combustion process occurs outside the main engine. This allows for the use of a wider variety of fuels, including pulverized coal or biomass, and in some designs, only clean air passes through the turbine, preventing contamination of the blades.

What are the main advantages of using gas turbines in surface vehicles like cars and buses?

Gas turbines offer a high power-to-weight ratio and a compact size compared to reciprocating engines. They also provide smoother operation with less vibration.

What were some of the challenges that prevented widespread adoption of gas turbines in automobiles?

Challenges included poor fuel efficiency at idle and low speeds, slow response to power demands (turbo lag), and higher manufacturing costs compared to mass-produced piston engines. Fuel consumption was a significant issue for many early automotive turbine experiments.

What was the significance of the Chrysler Turbine Car program?

Chrysler built fifty Chrysler Turbine Cars in 1963 and conducted the only consumer trial of gas turbine-powered cars. These vehicles featured a unique rotating recuperator (regenerator) to improve efficiency.

What was the Rover JET1, and what was its fate?

The Rover JET1, unveiled in 1950, was the first car powered by a gas turbine engine. While it achieved impressive speeds, fuel consumption issues made it impractical for mass production. It is now on display at the London Science Museum.

How were gas turbines used in racing cars, such as the STP-Paxton Turbocar?

The STP-Paxton Turbocar, powered by a Pratt & Whitney gas turbine, nearly won the 1967 Indianapolis 500. These cars demonstrated the high power potential of turbines but often faced reliability issues, like gearbox failures, or rule restrictions.

What are Auxiliary Power Units (APUs) in the context of gas turbines?

APUs are small gas turbines used to supply auxiliary power to larger machines, such as aircraft. They provide compressed air for air conditioning and engine starting, as well as mechanical or electrical power for other systems.

How do industrial gas turbines differ from aeronautical designs?

Industrial gas turbines are built with heavier construction for frames, bearings, and blading. They are also more integrated with the driven equipment, such as electric generators, and associated heat recovery systems.

What is a combined cycle power plant?

A combined cycle power plant utilizes waste heat from the gas turbine's exhaust to generate steam, which then drives a separate steam turbine. This configuration significantly increases overall thermal efficiency compared to a simple cycle gas turbine.

What are the main advantages of gas turbine engines listed in the article?

Key advantages include a high power-to-weight ratio, smaller size, smoother operation with less vibration, fewer moving parts leading to lower maintenance and higher reliability, usable waste heat for combined cycles or cogeneration, lower peak combustion pressures, low oil consumption, ability to run on various fuels, and low CO and HC emissions.

What are the main disadvantages of gas turbine engines mentioned?

Disadvantages include potentially high core engine costs due to exotic materials, lower efficiency at idle speeds, longer startup times, less responsiveness to power changes, and characteristic noise (whine or roar).

What is the role of Computational Fluid Dynamics (CFD) in gas turbine technology?

CFD is a key computational tool used in the design and development of gas turbines. It enhances understanding of complex fluid flow and heat transfer phenomena, leading to substantial improvements in component performance and overall engine efficiency.

How has the development of single-crystal superalloys impacted gas turbine design?

Single-crystal superalloys have significantly improved creep resistance in turbine blades. Their unique microstructure impedes dislocation motion, increasing the stress required for creep to begin and allowing for higher operating temperatures, which boosts efficiency.

What is the purpose of a recuperator (or regenerator) in a gas turbine?

A recuperator is a heat exchanger that recovers waste heat from the exhaust gases and uses it to preheat the compressed air before it enters the combustor. This preheating increases the overall thermal efficiency of the engine.

What is the primary reason gas turbines are well-suited for aircraft propulsion?

Their superior power-to-weight ratio is the primary reason. This allows for powerful engines that are relatively lightweight, which is crucial for aircraft performance.

How do microturbines differ from larger gas turbines in terms of rotational speed?

Microturbines spin at much higher rotational speeds. While large jet engines operate around 10,000-25,000 rpm, microturbines can spin as fast as 500,000 rpm to achieve the necessary blade tip speeds for efficient operation at their smaller scale.

What is the 'Hyperbar' system used in the French Leclerc tank?

The Hyperbar system replaces the tank's conventional turbocharger with a small gas turbine. This turbine acts as an assisted diesel exhaust turbocharger, providing boost independent of engine RPM and eliminating turbo lag, allowing for a smaller, lighter engine.

What were the early marine applications of gas turbines?

Early applications included the Royal Navy's motor gunboat MGB 2009 (converted in 1947) and the Steam Gun Boat Grey Goose (converted in 1952). The Bold class fast patrol boats, built in 1953, were the first ships designed specifically for gas turbine propulsion.

Why did gas turbines not replace diesel engines in large merchant ships, despite their advantages?

Diesel engines maintained a significant advantage in fuel economy at constant cruising speeds, which is a critical factor for commercial shipping operations. Gas turbines were more successful in naval vessels where rapid speed changes are essential.

What is the significance of ASME Performance Test Codes, such as PTC 22-2014, for gas turbines?

These codes standardize the procedures and definitions for testing gas turbines. A key characteristic is that they indicate the quality of the test through uncertainty measurements, rather than using these as commercial tolerances.

What role do foil bearings play in modern gas turbines?

Foil bearings were commercially introduced to gas turbines in the 1990s. They can withstand many start/stop cycles and have eliminated the need for traditional oil systems in some applications, like microturbines.

What is the purpose of a turbocharger, which is related to gas turbine technology?

A turbocharger is essentially a compact gas turbine driven by exhaust gas. It uses its turbine wheel to drive a compressor wheel, which forces more air into the engine's intake, thereby increasing power output.

How did the U.S. Clean Air Act Amendments of 1970 influence automotive gas turbine research?

The amendments spurred research funded by the U.S. government into developing automotive gas turbine technology. Companies like Chrysler, General Motors, Ford, and American Motors conducted design concepts and vehicle tests to meet emission regulations.

What is the main advantage of gas turbines for mechanical drive applications in industries like oil and gas?

In these industries, gas turbines are used to drive pumps and compressors. They offer a reliable and powerful solution for processes like gas injection into wells or compressing gas for transportation, often benefiting from readily available fuel sources.

What is the purpose of the afterburner in some gas turbine engines?

An afterburner is an addition to a gas turbine engine, typically in jet engines, that injects fuel directly into the hot exhaust gases. This ignites the unburnt fuel and air, significantly increasing thrust, though at the cost of much higher fuel consumption.

What are the main components of the 'gas generator' or core of a gas turbine?

The gas generator, or core, of a gas turbine consists of a compressor, a combustor, and a turbine that drives the compressor. This section is responsible for producing the high-temperature, high-pressure gas.

How does the size of a gas turbine affect its rotational speed?

Smaller gas turbines must rotate at higher speeds to achieve the necessary blade tip speeds for efficient compression and expansion. For example, microturbines can spin up to 500,000 rpm, whereas larger engines operate at much lower speeds.

What is the 'power turbine' in a gas turbine engine?

A power turbine is an additional turbine, separate from the one driving the compressor, that extracts the remaining energy from the exhaust gases. This power can then be used to drive external equipment like generators, propellers, or helicopter rotors.

What is the typical efficiency of a simple-cycle industrial gas turbine used solely for shaft power?

A simple-cycle gas turbine used only for shaft power typically has a thermal efficiency of about 30%. This efficiency can be significantly increased when integrated into combined cycle or cogeneration systems.

What is the significance of the Mitsubishi Heavy Industries M501J gas turbine tested in 2011?

The M501J was the first combined cycle gas turbine to achieve over 60% efficiency. This development marked a significant advancement in the efficiency of gas turbine technology.

What are the key advancements in gas turbine technology mentioned in the article?

Key advancements include computational fluid dynamics (CFD) for design, superior high-temperature materials like single-crystal superalloys, thermal barrier coatings, inter-cooling, regeneration, reheating, and improvements in emissions control and microelectronics for microturbines.

What is the purpose of the air that is ducted around the combustor in a gas turbine?

Approximately 70% of the air from the compressor is ducted around the main combustion zone. This air is used for cooling the combustor and turbine components, preventing them from overheating.

What is the 'thrust-to-weight ratio' and why is it important for flight?

Thrust-to-weight ratio is a measure of how much thrust an engine produces relative to its own weight. A higher thrust-to-weight ratio is desirable for aircraft propulsion, as it allows for better acceleration and climb performance.

What is the primary fuel used in most modern gas-fired power plants?

Natural gas is the primary fuel used in most modern gas-fired power plants, as indicated by the example of the Gateway Generating Station.

How does the 'yield strength anomaly' in single-crystal superalloys benefit gas turbine blades?

The yield strength anomaly means that certain superalloys become stronger at higher temperatures. This property enhances the creep resistance of turbine blades, allowing them to withstand the extreme conditions within the engine more effectively.

What is the function of the 'power turbine' in a turboshaft engine used for helicopters?

In a turboshaft engine for helicopters, the power turbine is typically used to drive the main rotor. It spins independently of the gas generator, allowing for optimized speeds for both components.

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Defining the Gas Turbine

Core Concept

A gas turbine engine, fundamentally, is a type of continuous flow internal combustion engine. It operates on the principle of the Brayton cycle, utilizing air as its working fluid to generate power.

The Brayton Cycle

The cycle involves four key thermodynamic processes: isentropic compression, isobaric combustion, isentropic expansion, and isobaric heat rejection. In practice, it's an open system where fresh air is continuously drawn in.

Operational Principle

Atmospheric air is compressed, fuel is injected and ignited, creating high-temperature gas. This gas expands through a turbine, driving the compressor and producing output shaft work or direct thrust.

Essential Components

Compressor

The initial stage, responsible for drawing in and compressing ambient air to a higher pressure. Designs include axial and centrifugal types, or a combination.

Combustor

Where fuel is mixed with the compressed air and ignited. This combustion process dramatically increases the temperature and volume of the gas mixture.

Turbine

The section where the high-temperature, high-pressure gas expands. This expansion drives the turbine blades, producing rotational energy primarily to power the compressor, with excess energy available for external work.

Theory of Operation

Brayton Cycle Dynamics

The ideal gas turbine operates on the Brayton cycle. Air is compressed (isentropic), heat is added at constant pressure (combustion), the gas expands (isentropic), and the cycle repeats without a formal heat rejection phase, as it's an open system.

Real-World Considerations

In practical applications, irreversible processes like friction and turbulence reduce efficiency. Combustion chambers add energy, increasing specific volume and slightly reducing pressure. Turbine expansion generates shaft work, with 60-70% typically consumed by the gas generator itself.

Energy Split

The engine's design dictates the energy distribution between shaft work (for driving generators, propellers, etc.) and exhaust thrust. This balance is crucial for optimizing performance based on the intended application.

Diverse Engine Types

Jet Engines

Optimized for thrust. Includes turbojets (direct exhaust thrust, less efficient) and turbofans (using a ducted fan for increased bypass air, higher efficiency and lower noise).

Turboprop/Turboshaft

Turboprops use a propeller driven by the turbine via a reduction gearbox. Turboshafts power rotors (helicopters) or transmissions, often featuring a free-turbine design for flexibility.

Industrial & Aeroderivative

Industrial turbines are robustly built for continuous operation (power generation, mechanical drive). Aeroderivatives are lighter, based on aircraft engines, offering faster response times for power generation and marine use.

Microturbines

Compact units (25-500 kW) derived from turbochargers or APUs. They offer high combined heat and power efficiency but lower simple-cycle efficiency without recuperation.

Key Applications

Aerospace

The primary domain for jet, turboprop, and turboshaft engines, valued for their high power-to-weight ratio, enabling efficient flight across various altitudes and speeds.

Power Generation

Widely used for electricity generation, especially in combined cycle (CCGT) and cogeneration (CHP) configurations, achieving high thermal efficiencies (over 60% in advanced models).

Marine Propulsion

Found in naval vessels and some high-speed ferries, prized for rapid acceleration and compact size. Challenges include corrosion and fuel economy at cruising speeds.

Land Vehicles

Used in tanks (e.g., M1 Abrams, T-80) for power density, and explored in concept cars and hybrid vehicles. Challenges remain in fuel efficiency, response time, and cost compared to piston engines.

Historical Development

Early Concepts

Ancient principles were explored by Hero of Alexandria (aeolipile) and Leonardo da Vinci (smoke jack). John Barber patented the first true gas turbine concept in 1791.

1791: John Barber patents the first gas turbine design.
1894: Charles Parsons patents steam turbine propulsion.
1903: Ægidius Elling builds the first gas turbine producing net power.
1930: Frank Whittle patents the turbojet design.

Jet Age Dawn

The 1930s saw crucial developments with Whittle's and Hans von Ohain's turbojet prototypes. The Junkers Jumo 004 powered the first operational military jets (Me 262) in 1944.

1937: First successful test runs of Whittle's and von Ohain's engines.
1939: First 4 MW utility power generation turbine by Brown Boveri.
1944: Junkers Jumo 004 enters production, powering early jets.
1947: First marine gas turbine trials on HMS M.G.B. 2009.

Modern Advancements

Post-WWII saw widespread adoption in aviation, power generation, and marine applications. Innovations include combined cycles, advanced materials, and microturbines.

1950s: Gas turbines explored in concept cars (Rover JET1, GM Firebird).
1960s: Combined cycle and combined diesel-gas systems emerge.
1990s: Single-crystal blade technology increases efficiency.
2010s: Efficiencies exceed 60% in advanced combined cycle configurations.

Technological Advancements

Computational Design

Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) enable sophisticated design optimization, improving component performance and understanding complex flow phenomena.

Advanced Materials

High-temperature superalloys, often single-crystal, and thermal barrier coatings (TBCs) allow higher operating temperatures, boosting efficiency and durability while mitigating creep.

Efficiency & Emissions

Continuous improvements push turbine inlet temperatures (e.g., 1600°C) and compression ratios (e.g., GE9X at 61:1). Focus is on increasing efficiency while reducing NOx emissions through advanced combustion techniques.

Advantages & Disadvantages

Advantages

High power-to-weight ratio.
Compact size compared to piston engines.
Smooth operation, low vibration.
Fewer moving parts, potentially lower maintenance.
High reliability for sustained output.
Usable exhaust heat for combined cycles/CHP.
Lower peak combustion pressures.
Can use diverse fuels.
Low CO/HC emissions due to excess air.

Disadvantages

High initial cost, especially for high-reliability applications.
Lower efficiency at idle and low speeds.
Longer startup times than piston engines.
Less responsive to rapid power demand changes.
Characteristic high-frequency noise ("whine").
Turbine blades sensitive to contaminants (dust, sand).

Major Manufacturers

Global Leaders

The gas turbine industry is dominated by several key international manufacturers specializing in aerospace, power generation, and industrial applications.

GE Aerospace / GE Vernova
Rolls-Royce Holdings
Siemens Energy
Mitsubishi Heavy Industries
Ansaldo Energia
Solar Turbines
MAN Turbo
Pratt & Whitney / Pratt & Whitney Canada
Doosan Enerbility
MAPNA Group
United Engine Corporation (ODK)
Zorya-Mashproekt
Aero Engine Corporation of China (AECC)
IHI Corporation

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References

UK patent no. 1833 â Obtaining and Applying Motive Power, & c. A Method of Rising Inflammable Air for the Purposes of Procuring Motion, and Facilitating Metallurgical Operations

Bakken, Lars E et al., p.83-88. "Centenary of the First Gas Turbine to Give Net Power Output: A Tribute to Ãgidius Elling". ASME. 2004

Eckardt, D. and Rufli, P. "Advanced Gas Turbine Technology â ABB/ BBC Historical Firsts", ASME J. Eng. Gas Turb. Power, 2002, p. 124, 542â549

Christopher, John. The Race for Hitler's X-Planes (The Mill, Gloucestershire: History Press, 2013), p.74.

Latief, F. H.; Kakehi, K. (2013) "Effects of Re content and crystallographic orientation on creep behavior of aluminized Ni-based single crystal superalloys". Materials & Design 49 : 485â492

Caron P., Khan T. "Evolution of Ni-based superalloys for single crystal gas turbine blade applications"

"History of Chrysler Corporation Gas Turbine Vehicles" published by the Engineering Section 1979

"Chrysler Corp., Exner Concept Cars 1940 to 1961" undated, retrieved on 11 May 2008.

Fast missile boat

Naval Education and Training Program Development Center Introduction to Marine Gas Turbines (1978) Naval Education and Training Support Command, pp. 3.

National Research Council (U.S.) Innovation in the Maritime Industry (1979) Maritime Transportation Research Board, pp. 127â131

A full list of references for this article are available at the Gas turbine Wikipedia page

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Disclaimer

Important Notice

This page was generated by an Artificial Intelligence and is intended for informational and educational purposes only. The content is based on a snapshot of publicly available data from Wikipedia and may not be entirely accurate, complete, or up-to-date.

This is not professional engineering advice. The information provided on this website is not a substitute for professional engineering consultation, design, or analysis. Always refer to official manufacturer documentation and consult with qualified engineers for specific applications or technical requirements.

The creators of this page are not responsible for any errors or omissions, or for any actions taken based on the information provided herein.

Gas Turbine Dynamics

💡 Dive in with Flashcard Learning! 💡

Defining the Gas Turbine ⚙️

🔥 Core Concept

🔄 The Brayton Cycle

💨 Operational Principle

Essential Components 🧩

🌀 Compressor

🔥 Combustor

⚙️ Turbine

Theory of Operation 🔬

📈 Brayton Cycle Dynamics

🌡️ Real-World Considerations

⚖️ Energy Split

Diverse Engine Types ✈️

🚀 Jet Engines

⚓ Turboprop/Turboshaft

🏭 Industrial & Aeroderivative

💡 Microturbines

Key Applications 🌍

✈️ Aerospace

💡 Power Generation

🚢 Marine Propulsion

🚗 Land Vehicles

Historical Development 📜

⏳ Early Concepts

✈️ Jet Age Dawn

⚡ Modern Advancements

Technological Advancements 💡

💻 Computational Design

💎 Advanced Materials

🌡️ Efficiency & Emissions

Advantages & Disadvantages ⚖️

👍 Advantages

👎 Disadvantages

Major Manufacturers 🏢

🌐 Global Leaders

Teacher's Corner 🧑‍🏫

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References

📜 References

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Disclaimer ⚠️

📜 Important Notice

Dive in with Flashcard Learning!

Defining the Gas Turbine

Core Concept

The Brayton Cycle

Operational Principle

Essential Components

Compressor

Combustor

Turbine

Theory of Operation

Brayton Cycle Dynamics

Real-World Considerations

Energy Split

Diverse Engine Types

Jet Engines

Turboprop/Turboshaft

Industrial & Aeroderivative

Microturbines

Key Applications

Aerospace

Power Generation

Marine Propulsion

Land Vehicles

Historical Development

Early Concepts

Jet Age Dawn

Modern Advancements

Technological Advancements

Computational Design

Advanced Materials

Efficiency & Emissions

Advantages & Disadvantages

Advantages

Disadvantages

Major Manufacturers

Global Leaders

Teacher's Corner

True or False?

Test Your Knowledge!

Gamer's Corner

Discover other topics to study!

References

Feedback & Support

Disclaimer

Important Notice