A gas turbine, also called a combustion turbine, is a rotary engine The rotary engine was an early type of internal-combustion engine, usually designed with an odd number of cylinders per row in a radial configuration, in which the crankshaft remained stationary and the entire cylinder block rotated around it. The design was used mostly in the years shortly before and during World War I to power aircraft, and also that extracts energy In physics, energy is a quantity that is often understood as the ability to perform work. This quantity can be assigned to any particle, object, or system of objects as a consequence of its physical state from a flow of combustion Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame. Fuels of interest often include organic compounds in the gas, liquid or gas. It has an upstream compressor A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume coupled to a downstream turbine A turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work, and a combustion chamber in-between. Gas turbine may also refer to just the turbine A turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work component.

Energy In physics, energy is a quantity that is often understood as the ability to perform work. This quantity can be assigned to any particle, object, or system of objects as a consequence of its physical state is added to the gas stream in the combustor A combustor is a component or area of a gas turbine, ramjet, or scramjet engine where combustion takes place. It is also known as a burner or flame can. In a gas turbine engine, the main combustor or combustion chamber is fed high pressure air by the compression system and feeds the hot, high pressure exhaust into the turbine components of the, where fuel Fuel is any material that can be used to generate energy to produce mechanical work in a controlled manner. The processes used to convert fuel into energy include chemical reactions, such as combustion, and nuclear reactions, such as nuclear fission or nuclear fusion. Fuels are also used in the cells of organisms in a process known as metabolism is mixed with air The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night. Dry air contains roughly (by volume) 78% nitrogen, 21% and ignited An ignition system is a system for igniting a fuel-air mixture. It is best known in the field of internal combustion engines but also has other applications, e.g. in oil-fired and gas-fired boilers. The earliest internal combustion engines used a flame, or a heated tube, for ignition but these were quickly replaced by systems using an electric. In the high pressure environment of the combustor, combustion of the fuel increases the temperature Historically, two equivalent concepts of temperature have developed, the thermodynamic description and a microscopic explanation based on statistical physics. Since thermodynamics deals entirely with macroscopic measurements, the thermodynamic definition of temperature, first stated by Lord Kelvin, is stated entirely in empirical, measurable. The products of the combustion are forced into the turbine section. There, the high velocity In physics, velocity is the rate of change of displacement . It is a vector physical quantity; both magnitude and direction are required to define it. The scalar absolute value (magnitude) of velocity is speed, a quantity that is measured in meters per second (m/s or ms−1) when using the SI (metric) system and volume Volume is how much three-dimensional space a substance or shape occupies or contains, often quantified numerically using the SI derived unit, the cubic metre. The volume of a container is generally understood to be the capacity of the container, i. e. the amount of fluid (gas or liquid) that the container could hold, rather than the amount of of the gas flow is directed through a nozzle A nozzle is a mechanical device designed to control the direction or characteristics of a fluid flow as it exits an enclosed chamber or pipe via an orifice over the turbine's blades, spinning the turbine which powers the compressor and, for some turbines, drives their mechanical output. The energy given up to the turbine comes from the reduction in the temperature of the exhaust gas.

Energy is extracted in the form of shaft power, compressed air and thrust, in any combination, and used to power aircraft An aircraft is a vehicle which is able to fly by being supported by the air, or in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines, trains A train is a connected series of vehicles for rail transport that move along a track to transport freight or passengers from one place to another. The track usually consists of two rails, but might also be a monorail or maglev guideway, ships A ship ( Audio (help·info)) is a large vessel that floats on water. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships may be found on lakes, seas, and rivers and they allow for a variety of activities, such as the transport of people or goods, fishing, entertainment, public safety, and warfare, generators In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. The reverse conversion of electrical energy into mechanical energy is done by a motor; motors and generators have many similarities. A generator forces electrons in the windings to flow through the external electrical circuit. It is, and even tanks A tank is a tracked, armoured fighting vehicle designed for front-line combat which combines operational mobility and tactical offensive and defensive capabilities. Firepower is normally provided by a large-calibre main gun in a rotating turret and secondary machine guns, while heavy armour and all-terrain mobility provide protection for the tank.

History

• 150: Hero's Hero of Alexandria (Greek: Ἥρων ὁ Ἀλεξανδρεύς) (c. 10–70 AD). was an ancient Greek mathematician who was a resident of a Roman province (Ptolemaic Egypt); he was also an engineer who was active in his native city of Alexandria. He is considered the greatest experimenter of antiquity and his work is representative of the Engine (aeolipile An aeolipile , also known as a Hero engine, is a rocket style jet engine which spins when heated. In the first century AD, Hero of Alexandria described the device, and many sources give him the credit for its invention) — Apparently, Hero's steam engine was taken to be no more than a toy A toy is any object that can be used for play. Toys are usually associated with children and pets, but it is not unusual for adults and some other animals to play with toys. An example of this is a dolphin being trained to nudge a ball through a hoop. Many items are designed to serve as toys, but goods produced for other purposes can also be used, and thus its full potential not realized for centuries.
• 1500: The "Chimney Jack" was drawn by Leonardo da Vinci Leonardo di ser Piero da Vinci ( pronunciation ), (April 15, 1452 – May 2, 1519), was an Italian polymath: painter, sculptor, architect, musician, scientist, mathematician, engineer, inventor, anatomist, geologist, cartographer, botanist and writer. Leonardo has often been described as the archetype of the Renaissance man, a man whose which was turning a roasting spit. Hot air from a fire rose through a series of fans which connect and turn the roasting spit.
• 1551: Taqi al-Din invented a steam turbine A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles Parsons in 1884, which he used to power a self-rotating spit Rotisserie is a style of roasting where meat is skewered on a spit - a long solid rod used to hold food while it is being cooked over a fire in a fireplace or over a campfire, or roasted in an oven. This method is generally used for cooking large joints of meat or entire animals, such as pigs, turkeys, goats or historically, entire cattle. The.^[1]
• 1629: Jets of steam rotated a turbine that then rotated driven machinery allowed a stamping mill to be developed by Giovanni Branca Giovanni Branca was an Italian engineer and architect, chiefly remembered today for what some commentators have taken to be an early steam engine.
• 1678: Ferdinand Verbiest Father Ferdinand Verbiest was a Flemish Jesuit missionary in China during the Qing dynasty. He was born in Pittem near Tielt in Flanders, later part of the modern state of Belgium. He is known as Nan Huairen (南懷仁) in Chinese. He was an accomplished mathematician and astronomer and proved to the court of Kangxi Emperor that European astronomy built a model carriage relying on a steam jet for power.
• 1791: A patent was given to John Barber, an Englishman, for the first true gas turbine. His invention had most of the elements present in the modern day gas turbines. The turbine was designed to power a horseless carriage.^{[citation needed]}
• 1872: A gas turbine engine was designed by Dr. Franz Stolze, but the engine never ran under its own power.
• 1894: Sir Charles Parsons Sir Charles Algernon Parsons, OM was a British engineer, best known for his invention of the steam turbine. He worked as an engineer on dynamo and turbine design, and power generation, with great influence on the naval and electrical engineering fields. He also developed optical equipment, for searchlights and telescopes patented the idea of propelling a ship with a steam turbine, and built a demonstration vessel, the Turbinia Turbinia was the first steam turbine powered steamship. Built as an experimental vessel in 1894, and easily the fastest ship in the world at that time, Turbinia was demonstrated dramatically at the Spithead Navy Review in 1897 and set the standard for the next generation of steamships, the majority of which were turbine powered. The vessel can, easily the fastest vessel afloat at the time. This principle of propulsion is still of some use.
• 1895: Three 4-ton 100 kW Parsons radial flow generators were installed in Cambridge The city of Cambridge (pronounced /ˈkeɪmbrɪdʒ/ (KAYM-bridj)) is a university town and the administrative centre of the county of Cambridgeshire, England. It lies in East Anglia about 50 miles (80 km) north-by-east of London. Cambridge is also at the heart of the high-technology centre known as Silicon Fen – a play on Silicon Valley and the Power Station, and used to power the first electric street lighting scheme in the city.
• 1903: A Norwegian, Ægidius Elling, was able to build the first gas turbine that was able to produce more power than needed to run its own components, which was considered an achievement in a time when knowledge about aerodynamics was limited. Using rotary compressors and turbines it produced 11 hp (massive for those days). His work was later used by Sir Frank Whittle Air Commodore Sir Frank Whittle, OM, KBE, CB, FRS, Hon FRAeS was a British Royal Air Force (RAF) officer. Frank Whittle invented the jet engine in 1932, but does concede that Germany's Dr. Hans von Ohain independently also "invented" the jet engine years later. Whittle is hailed as a father of jet propulsion.
• 1906: The Armengaud-Lemale turbine engine in France with water-cooled combustion chamber.
• 1910: Holzwarth impulse turbine (pulse combustion) achieved 150 kilowatts.
• 1913: Nikola Tesla Nikola Tesla was an inventor, mechanical engineer, and electrical engineer. He was an important contributor to the birth of commercial electricity, and is best known for his many revolutionary developments in the field of electromagnetism in the late 19th and early 20th centuries. Tesla's patents and theoretical work formed the basis of modern patents the Tesla turbine The Tesla turbine is a bladeless centrifugal flow turbine expander patented by Nikola Tesla in 1913. It is referred to as a bladeless turbine because it uses the boundary layer effect and not a fluid impinging upon the blades as in a conventional turbine. The Tesla turbine is also known as the boundary layer turbine, cohesion-type turbine, and based on the Boundary layer In physics and fluid mechanics, a boundary layer is that layer of fluid in the immediate vicinity of a bounding surface. In the Earth's atmosphere, the planetary boundary layer is the air layer near the ground affected by diurnal heat, moisture or momentum transfer to or from the surface. On an aircraft wing the boundary layer is the part of the effect.
• 1914: Application^[where?] for a gas turbine engine filed by Charles Curtis.^{[citation needed]}
• 1918: One of the leading gas turbine manufacturers of today, General Electric The General Electric Company, or GE , is an American multinational conglomerate corporation incorporated in the State of New York. In 2010, Forbes ranked GE as the world's second largest company, based on a formula that compared the total sales, profits, assets, and market value of several multinational companies. The company has 304,000 employees, started their gas turbine division.
• 1920: The practical theory of gas flow through passages was developed into the more formal (and applicable to turbines) theory of gas flow past airfoils by Dr. A. A. Griffith.
• 1930: Sir Frank Whittle Air Commodore Sir Frank Whittle, OM, KBE, CB, FRS, Hon FRAeS was a British Royal Air Force (RAF) officer. Frank Whittle invented the jet engine in 1932, but does concede that Germany's Dr. Hans von Ohain independently also "invented" the jet engine years later. Whittle is hailed as a father of jet propulsion patented the design for a gas turbine for jet propulsion A jet engine is a reaction engine that discharges a fast moving jet of fluid to generate thrust in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets and pump-jets. In general, most jet engines are internal combustion engines but non-combusting forms also exist. His work on gas propulsion relied on the work from all those who had previously worked in the same field and he has himself stated that his invention would be hard to achieve without the works of Ægidius Elling. The first successful use of his engine was in April 1937.
• 1934: Raúl Pateras de Pescara patented the free-piston engine The free-piston engine is a linear, 'crankless' internal combustion engine, in which the piston motion is not controlled by a crankshaft but determined by the interaction of forces from the combustion chamber gases, a rebound device and a load device (e.g. a gas compressor or a linear alternator) as a gas generator for gas turbines.
• 1936: Hans von Ohain and Max Hahn in Germany developed their own patented engine design at the same time that Sir Frank Whittle Air Commodore Sir Frank Whittle, OM, KBE, CB, FRS, Hon FRAeS was a British Royal Air Force (RAF) officer. Frank Whittle invented the jet engine in 1932, but does concede that Germany's Dr. Hans von Ohain independently also "invented" the jet engine years later. Whittle is hailed as a father of jet propulsion was developing his design in England.^{[citation needed]}
• 1939: First gas turbine power generator, designed by Aurel Stodola, for Brown Boveri company.

Theory of operation

Gas turbines are described thermodynamically In science, thermodynamics is the study of energy conversion between heat and mechanical work, and subsequently the macroscopic variables such as temperature, volume and pressure by the Brayton cycle The Brayton cycle is a thermodynamic cycle that describes the workings of the gas turbine engine, basis of the jet engine and others. It is named after George Brayton , the American engineer who developed it, although it was originally proposed and patented by Englishman John Barber in 1791. It is also sometimes known as the Joule cycle. The, in which air is compressed isentropically In thermodynamics, an isentropic process or isoentropic process (ισον = "equal" ; εντροπία entropy = "disorder"(Greek)) is one in which for purposes of engineering analysis and calculation, one may assume that the process takes place from initiation to completion without an increase or decrease in the entropy of the, combustion Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame. Fuels of interest often include organic compounds in the gas, liquid or occurs at constant pressure, and expansion over the turbine occurs isentropically back to the starting pressure.

In practice, friction and turbulence cause:

1. non-isentropic compression: for a given overall pressure ratio, the compressor delivery temperature is higher than ideal.
2. non-isentropic expansion: although the turbine temperature drop necessary to drive the compressor is unaffected, the associated pressure ratio is greater, which decreases the expansion available to provide useful work.
3. pressure losses in the air intake, combustor and exhaust: reduces the expansion available to provide useful work.

As with all cyclic heat engines A heat engine is a physical device that converts thermal energy to mechanical output. The mechanical output is called work, and the thermal energy input is called heat. Heat engines typically run on a specific thermodynamic cycle. Heat engines can be open to the atmospheric air or sealed and closed off to the outside, higher combustion temperature means greater efficiency Fuel efficiency, is a form of thermal efficiency, meaning the efficiency of a process that converts chemical potential energy contained in a carrier fuel into kinetic energy or work. Overall fuel efficiency may vary per device, which in turn may vary per application, and this spectrum of variance is often illustrated as a continuous energy profile. The limiting factor is the ability of the steel, nickel, ceramic, or other materials that make up the engine to withstand heat and pressure. Considerable engineering goes into keeping the turbine parts cool. Some turbines also try to recover exhaust heat, which otherwise is wasted energy. Recuperators are heat exchangers A heat exchanger is a device built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact. They are widely used in space heating, refrigeration, air conditioning, power plants, chemical plants, petrochemical plants, petroleum refineries, natural that pass exhaust heat to the compressed air, prior to combustion. Combined cycle A combined cycle is characteristic of a power producing engine or plant that employs more than one thermodynamic cycle. Heat engines are only able to use a portion of the energy their fuel generates . The remaining heat (e.g., hot exhaust fumes) from combustion is generally wasted. Combining two or more thermodynamic cycles, such as the Brayton designs pass waste heat to steam turbine systems. And combined heat and power (co-generation) uses waste heat for hot water production.

Mechanically, gas turbines can be considerably less complex than internal combustion piston engines. Simple turbines might have one moving part: the shaft/compressor/turbine/alternative-rotor assembly (see image above), not counting the fuel system. However, the required precision manufacturing for components and temperature resistant alloys necessary for high efficiency often make the construction of a simple turbine more complicated than piston engines.

More sophisticated turbines (such as those found in modern jet engines) may have multiple shafts (spools), hundreds of turbine blades, movable stator blades, and a vast system of complex piping, combustors and heat exchangers.

As a general rule, the smaller the engine the higher the rotation rate of the shaft(s) needs to be to maintain top speed. Turbine blade top speed determines the maximum pressure that can be gained,this produces the maximum power possible independent of the size of the engine. Jet engines operate around 10,000 rpm and micro turbines around 100,000 rpm.

Thrust bearings and journal bearings are a critical part of design. Traditionally, they have been hydrodynamic oil bearings, or oil-cooled ball bearings. These bearings are being surpassed by foil bearings, which have been successfully used in micro turbines and auxiliary power units.

Types of gas turbines

Aeroderivatives and jet engines

Airbreathing jet engines are gas turbines optimized to produce thrust from the exhaust gases, or from ducted fans connected to the gas turbines. Jet engines that produce thrust primarily from the direct impulse of exhaust gases are often called turbojets, whereas those that generate most of their thrust from the action of a ducted fan are often called turbofans or (rarely) fan-jets.

Gas turbines are also used in many liquid propellant rockets, the gas turbines are used to power a turbopump to permit the use of lightweight, low pressure tanks, which saves considerable dry mass.

Aeroderivatives are also used in electrical power generation due to their ability to startup, shut down, and handle load changes more quickly than industrial machines. They are also used in the marine industry to reduce weight. The GE LM2500 and LM6000 are two common models of this type of machine.

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