Gas-turbine engine

A gas-turbine engine, or, informally, a gas turbine, is a type of continuous flow internal combustion engine. It has three main parts that work together to create power: a rotating gas compressor, a combustor, and a compressor-driving turbine.

To make it work for different uses, extra parts are added. For airplanes, a propelling nozzle helps create thrust for flight. For other uses like helicopters or land vehicles, an extra turbine is added to power rotors, wheels, or generators.

Gas turbines work by using a process called the Brayton cycle. Air is squeezed by the compressor, fuel is added and burned to create hot, high-pressure gas, and this gas spins a turbine to make power. The leftover energy in the exhaust can be used to push the airplane forward or to power other machines.

These engines are very important because they are used to power many things, including aircraft, trains, ships, electric generators, pumps, gas compressors, and even tanks. They are chosen for their ability to produce a lot of power while being relatively light, which is especially useful for vehicles that need to move quickly or travel long distances.

Timeline of development

• 50: Early records show Hero's engine, called the aeolipile. It was more of a curious toy but showed an important physics idea used in today’s turbine engines.
• 1000: The Chinese used the "Trotting Horse Lamp" (Chinese: 走马灯, zŏumădēng) at lantern fairs. When lit, hot air rises and moves figures on a wheel, casting shadows on a screen.
• 1500: Leonardo da Vinci drew a Smoke jack. Hot air from a fire turned a turbine connected to a roasting spit.
• 1791: John Barber, an Englishman, received a patent for the first true gas turbine. It was meant to power a horseless carriage.
• 1894: Sir Charles Parsons patented using a steam turbine to move ships and built a fast demonstration ship called the Turbinia.
• 1899: Charles Gordon Curtis patented the first gas-turbine engine in the US.
• 1900: Sanford Alexander Moss wrote about gas turbines for his thesis. Later, he worked at General Electric in Lynn, Massachusetts on improving engines.
• 1903: A Norwegian, Ægidius Elling, built the first gas turbine that produced more power than it used to run itself, a big step at the time.
• 1904: Franz Stolze built and tested a gas-turbine engine in Berlin, but it was not efficient enough to work well on its own.
• 1906: The Armengaud–Lemale gas turbine was tested in France. It could keep itself running but was not strong enough to do useful work.
• 1910: The first working Holzwarth gas turbine produced 150 kW (200 hp). It was planned to make much more power but was less efficient than other engines of the time.
• 1920s: Scientist A. A. Griffith developed theories about how air moves over airplane wings, which helped design better turbine engines.
• 1930: Frank Whittle patented a design for a gas turbine to power airplanes. His first successful test run happened in England in April 1937.
• 1932: The Brown Boveri Company in Switzerland began selling special engines for making steam, using the gas-turbine idea.
• 1936: The first constant-flow industrial gas turbine started working at Sun Oil’s refinery in Marcus Hook, Pennsylvania, US.
• 1937: Test versions of jet engines ran in the UK (by Frank Whittle) and Germany (by Hans von Ohain’s Heinkel HeS 1). The UK government gave money to continue developing Whittle’s engine.
• 1939: The first big gas turbine for making electricity was built in Switzerland. The world’s first jet airplane, the Heinkel He 178, flew for the first time.
• 1940: The Jendrassik Cs-1, a new kind of engine, ran for the first time. It was meant for a Hungarian fighter plane but was never used in an actual airplane.
• 1944: The Junkers Jumo 004 engine went into production, powering Germany’s first jet fighters like the Messerschmitt Me 262. This started the use of gas turbines in airplanes.
• 1946: Scientists in the UK and Switzerland joined forces. In Switzerland, the first big commercial gas turbine started operating.
• 1947: A gas turbine was used on a Royal Navy boat for the first time.
• 1995: Siemens started using a new kind of turbine blade in their big electricity-making engines, making them more efficient.
• 2011: Mitsubishi Heavy Industries tested a very efficient gas turbine for making electricity.

Theory of operation

Air is taken in by a compressor, called a gas generator, and moves into a combustor. In the combustor, air mixes with fuel and ignites, creating hot gases that expand and flow through a turbine. This spinning motion creates power.

The main benefit of gas-turbine engines is their strength compared to their weight, making them ideal for use in aircraft. These engines can be simpler than other types, with fewer moving parts, but more advanced versions have many detailed components to improve performance.

Types

Jet engines

Main article: Jet engine

Jet engines are a type of gas turbine made to push air backward to create forward thrust. These engines can work with or without added fans in front. Engines with fans are called turbofans and make less noise and use less fuel. They have two types based on how much air the fan moves. These engines are often used in airplanes.

Gas turbines are also used in some rockets to help pump fuel, allowing the rocket to be lighter.

Turboprop engines

Main article: Turboprop

Turboprop engines are gas turbines that power airplane propellers through a gear system. This lets the engine be smaller while still very powerful. These engines are used in small passenger planes, cargo planes, and some big military planes. Two common engines are the Pratt & Whitney Canada PT6 and the Honeywell TPE331.

Aeroderivative gas turbines

Aeroderivative gas turbines are smaller versions of airplane engines, used for making electricity or on ships to save weight. Examples include the General Electric LM2500 and General Electric LM6000.

Amateur gas turbines

More people are now using or building their own small gas turbines. Some use old military engines for shows, while others build very simple versions from car parts or even from scratch. Small companies now sell tiny turbines for model airplanes.

Auxiliary power units

Small gas turbines can be used to give power to big vehicles like airplanes. They provide compressed air for cooling, start bigger engines, and give electricity or other power to devices on the plane.

Industrial gas turbines for power generation

See also: Gas-fired power plant

Big gas turbines used for making electricity are built stronger than airplane engines and are often connected to generators. They can be very small or huge systems in special buildings. When used only to make power, they are about 30% efficient, but they can be more efficient when used with other systems to also make heat.

Gas turbines can also be used with other machines to make even more electricity and heat. They can start up quickly to give power when needed most. These are often used when there isn’t enough regular power available.

Industrial gas turbines for mechanical drive

Big gas turbines used for moving machines instead of making electricity are often smaller and have two shafts. They are mainly used in oil and gas industries to push gas through pipes or to power platforms in the ocean.

Compressed-air energy storage

Main article: Compressed-air energy storage

A new idea uses stored compressed air to power a turbine when needed, improving efficiency.

Turboshaft engines

Main article: Turboshaft

Turboshaft engines are used to power compressors in gas stations and plants that turn natural gas into liquid. They are also used in helicopters and big airplanes to give extra power.

Radial gas turbines

Main article: Radial turbine

Scale jet engine

Small jet engines, sometimes called micro-jets, use a special type of compressor. One early example was built by Kurt Schreckling and can make a small amount of thrust. These can be built by people with basic tools.

Microturbines

Main article: Microturbine

Microturbines are small turbines from 25 to 500 kilowatts, about the size of a refrigerator. They can be quite efficient, especially when used to make both electricity and heat at the same time.

External combustion

Most gas-turbine engines are internal combustion engines, but it is also possible to make an external combustion gas turbine. These are like a turbine version of a hot-air engine and are often called EFGT (externally-fired gas turbine) or IFGT (indirectly-fired gas turbine).

External combustion can use fuels like pulverized coal or finely ground biomass, such as sawdust. In the indirect system, a heat exchanger is used so that only clean air passes through the turbine. This means the turbine blades are not exposed to combustion products, allowing the use of cheaper fuels. However, the thermal efficiency is lower in this type of system. Some special gas turbines using helium or supercritical carbon dioxide could be useful for future solar and nuclear power generation.

In surface vehicles

Gas turbines are often used on ships, locomotives, helicopters, and tanks and, to a lesser extent, on cars, buses, and motorcycles.

Gas turbines can provide a lot of power in a small and light package. However, they are not as responsive or efficient as smaller piston engines for the range of speeds and power needed in vehicles. In series hybrid vehicles, this problem is less important because the electric motors are separate from the engine that makes electricity. The turbine can run at its best speed, and batteries and ultracapacitors can supply power when needed. The engine can be turned on and off to run only when it is most efficient. The development of continuously variable transmission may also help with the responsiveness issue.

Historically, turbines have been more expensive to make than piston engines. This is partly because piston engines have been made in huge numbers for many decades, while small gas-turbine engines are rare. However, turbines are made in large numbers in the form of turbochargers.

Marine applications

Main article: Marine propulsion

Gas turbines are used in many naval vessels because they provide a lot of power for their weight, helping ships move quickly and get moving fast.

The first naval ship to use a gas turbine was the Royal Navy's motor gunboat MGB 2009, which was converted in 1947. The German Navy launched its first Köln-class frigate in 1961 with gas turbines. The Soviet Navy made the first large ships powered only by gas turbines in 1962.

In civilian use, the oil tanker Auris was the first merchant ship to use a gas turbine in 1951. It operated well but was not as fuel-efficient as diesel engines. Some passenger ships and ferries later used gas turbines, but high fuel costs often made them less practical.

Advances in technology

Gas-turbine technology keeps getting better. Engineers are making engines that are smaller, more powerful, and more efficient. They use special computer programs to design these engines and create new materials that can handle very high temperatures. These improvements help engines work better and use fuel more wisely.

Computers help engineers understand how air and heat move through the engine, making design even better. Some engines now can reach very high temperatures while using less fuel and creating fewer harmful emissions. New types of parts, like foil bearings, make engines easier to maintain. Recent developments include very efficient engines with high compression ratios.

Advantages and disadvantages

Gas-turbine engines have several benefits and some drawbacks. One big advantage is that they can produce a lot of power while being lighter and smaller than many other engines. They also run more smoothly, with fewer parts that need fixing, making them reliable for long periods. These engines can use many different fuels and create less harmful smoke compared to some other engines.

However, gas-turbine engines can be expensive to build, especially for use in airplanes. They are not as efficient when sitting still and take longer to start up than other engines. They can also be less quick to change how much power they are using, and they make a loud whirring noise that can be hard to quiet down.

Major manufacturers

Many companies around the world make gas-turbine engines. Some of the biggest ones include Aero Engine Corporation of China, Alstom, Ansaldo Energia, Bharat Heavy Electricals Limited, Doosan Enerbility, GE Aerospace, GE Vernova, Hanwha Aerospace, Harbin Electric, Hindustan Aeronautics Limited, Howmet Aerospace, IHI Corporation, Kawasaki Heavy Industries, MAN Turbo, MAPNA Group, Mitsubishi Heavy Industries, MTU Aero Engines, Rolls-Royce Holdings, Power Machines, Pratt & Whitney, Pratt & Whitney Canada, Shanghai Electric, Siemens Energy, Solar Turbines, United Engine Corporation, and Zorya-Mashproekt. These companies help build the engines that power airplanes, power plants, and more.

Testing

Different countries and groups have special rules to test gas-turbine engines. These rules help make sure everyone agrees on how well the engines work. In the United States, a group called ASME made some important test rules for gas turbines, like ASME PTC 22–2014. These rules are used around the world. One big idea in these rules is that how exact the test results are shows how good the test was, not just a small allowed difference for business purposes.