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• California Distributed Energy Resource guide - Microturbine generators

• First Marine Gas Turbine 1947

• Introduction to how a gas turbine works from "how stuff works.com"

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turbine

Dictionary: tur·bine (tûr'bĭn, -bīn') Sponsored Links Turbine Engines

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Home > Library > Literature & Language > Dictionary n.

Any of various machines in which the kinetic energy of a moving fluid is converted to mechanical power by the impulse or reaction of the fluid with a series of buckets, paddles, or blades arrayed about the circumference of a wheel or cylinder.

[French, from Latin turbō, turbin-, spinning top, perhaps from Greek turbē, turmoil.]

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Columbia Encyclopedia: turbine Top

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turbine, rotary engine that uses a continuous stream of fluid (gas or liquid) to turn a shaft that can drive machinery.

A water, or hydraulic, turbine is used to drive electric generators in hydroelectric power stations. The first such station was built in Wisconsin in 1882. In a hydraulic turbine falling water strikes a series of blades or buckets attached around a shaft, causing the shaft to rotate, this motion in turn being used to drive the rotor of an electric generator. The three most common types of hydraulic turbine are the Pelton wheel, the Francis turbine, and the Kaplan turbine. Toward the end of the 19th cent. two engineers, Sir Charles A. Parsons of Great Britain and Carl G. P. de Laval of Sweden, were pioneers in the building of steam turbines. Continual improvements of their basic machines have caused steam turbines to become the principal power sources used to drive most large electric generators and the propellers of most large ships.

A steam turbine typically consists of a roughly conical, steel shell enclosing a central shaft along which a series of bladed disks are spaced like washers. The blades are curved and extend radially outward from the rim of each disk. In some steam turbines the shaft is surrounded by a drum to which the rows of blades are attached. Between each pair of disks is a row of stationary vanes attached to the steel shell and extending radially inward. Each set of stationary vanes and the bladed disk immediately next to it constitutes a stage of the turbine; most steam turbines are multistage engines.

At the inlet end of the turbine high-pressure steam enters from a boiler and moves through the turbine parallel to the shaft, first striking a row of stationary vanes that directs the steam against the first bladed disk at an optimum speed and angle. The steam then passes through the

remaining stages, forcing the disks and the shaft to rotate. At one end of the turbine the shaft sticks out and can be attached to machinery. A large steam turbine unit may actually be composed of several turbines that are all using the same shaft and steam. Such a unit might consist of a small, high-pressure turbine, connected to a larger, intermediate-pressure turbine, connected to a still larger, low-pressure turbine. After the steam leaves the turbine, it is sent to a condenser where it is converted back into water before being returned to the boiler.

Gas turbines are used mainly as aircraft engines. Some are used to drive electric generators, as in a gas turbine–electric locomotive, and high-speed tools. The term gas turbine is usually applied to a unit whose essential components are a compressor, a combustion chamber, and a turbine that resembles a steam turbine. The turbine drives the compressor, which feeds high-pressure air into the combustion chamber; there it is mixed with a fuel and burned, providing high-pressure gases to drive the turbine, the gases expanding until their pressure drops to atmospheric pressure. In a turboprop engine the turbine is used to turn a propeller as well as the compressor. In a turbojet engine only a small pressure drop is used to drive the turbine, the majority of the pressure drop occurring as the gases are expelled directly out of the engine. A variation of the turbojet is known as the turbofan engine.

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Essay: The perfect engine: the turbine Top

Turbines are devices that spin in the presence of a moving fluid. The difference between water wheels or windmills and turbines is largely one of emphasis and degree. During the 18th and 19th centuries, much progress was made toward extracting the kinetic energy of flowing water by devising water turbines. Leonhard Euler, applying fluid mechanics, developed a water turbine as early as 1750. During the 18th century several engineers, such as Benôit Fourneyron,

succeeded in building water turbines that by far outstripped conventional water wheels by giving the blades special shapes. The term "turbine" was coined by Fourneyron's professor Claude Burdin; he derived the term from turbo, a spinning object.

The most useful turbines for many purposes are those that can be propelled with energy from heat. A typical turbine based on heat is the steam turbine. The idea of a steam turbine is much older than the steam engine itself. Around 60 BCE the Alexandrian Greek Heron (a.k.a. Hero)

used jets of steam to turn a kettle. In 1629 the Italian engineer Giovanni Branca depicted in his machine book Le Machine a steam turbine in which a jet of steam is directed at the vanes of the same sort of apparatus as a water wheel. No doubt others observed that escaping steam is like the rushing wind and could be used to push mills just as the wind powers windmills.

When practical steam engines were built at the start of the 18th century, however, they moved a cylinder back and forth (reciprocating motion) instead of pushing a wheel around, although they could be made to turn wheels with various ingenious mechanisms. Reciprocating steam engines were bulky, had slow rotation speeds, and wasted much energy in the machine itself to move the heavy pistons back and forth. When first used to drive electric generators, reciprocating steam engines proved difficult to maintain at a fixed rotation speed as the load on the generator changed.

Turbines are as simple as reciprocating engines are complex. Because they have essentially only one moving part, they are sometimes called the perfect engines, almost directly turning heat into rotary motion.

The first to build a steam turbine was the British engineer Charles Algernon Parsons. In 1884 he completed a small turbine that rotated at 18,000 revolutions per minute and that delivered 10 horsepower. The Swedish engineer Carl Gustav de Laval, experimenting with steam turbines, achieved greater power and higher rotation rates. In 1890 he built a turbine consisting of a 30-cm (12-in.) disk with 200 blades mounted on a flexible axis. The steam was admitted to the blades by special nozzles (Laval nozzles) that accelerated the steam to very high velocities, thus transferring the energy of the steam in the form of kinetic energy to the blades.

The design of steam turbines developed into a science near the end of the 19th century. Better materials allowed the construction of turbine blades that are resistant to corrosion. Charles Curtis developed the multistage turbine in which the blades and disks become progressively larger when the steam expands. Parsons developed in 1894 the ship turbine engine. The slow-revolving turbine consisted of several sections of increasing diameter. High-pressure steam is admitted to the turbine and pressure differences in each section drive the turbine blades. The first ship to be equipped with such a steam turbine, the Turbinia, immediately established a speed record with 31 knots (57.5 km or 35.7 mi per hour). During the early years of the 20th century, most

reciprocating steam engines were replaced by steam turbines (or by diesels). Steam turbines can deliver much more power than reciprocating engines and need less maintenance. Steam turbines also supplanted marine steam engines on ships.

A similar evolution took place for large internal combustion engines, mainly driven by the need for lightweight and powerful airplane engines. Most large modern airplanes are now powered by

either turboprop or turbojet engines. These turbines are spun by the expansion of jet fuel instead of by the expansion of water into steam.

turbine

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