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turbine

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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turbine

turbine Rotary device turned by a moving fluid (liquid or gas). The modern form of water turbine is like a many-bladed propeller and is used to generate hydroelectricity. In power stations that burn fuels to produce electricity, the energy released by the burning is harnessed by the blades of jet engine-like steam turbines. As they spin, the turbines turn generators that produce electricity. Modern wind generators produce electricity when the wind turns their rotors. In gas turbines, hot gases from burning fuel turn turbines that can operate generators or other machinery.

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turbine

tur·bine / ˈtərˌbīn; -bin/ • n. a machine for producing continuous power in which a wheel or rotor, typically fitted with vanes, is made to revolve by a fast-moving flow of water, steam, gas, air, or other fluid.

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turbine

turbine XIX. — F., — L. turbō, -bin- (see prec.). Comb. form turbo- XIX.

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turbine

turbinealign, assign, benign, brine, chine, cline, combine, condign, confine, consign, dine, divine, dyne, enshrine, entwine, fine, frontline, hardline, interline, intertwine, kine, Klein, line, Main, malign, mine, moline, nine, on-line, opine, outshine, pine, Rhein, Rhine, shine, shrine, sign, sine, spine, spline, stein, Strine, swine, syne, thine, tine, trine, twine, Tyne, underline, undermine, vine, whine, wine •Sabine • carbine • Holbein • woodbine •concubine • columbine • turbine •sardine • Aldine • muscadine •celandine • anodyne • androgyne

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Turbine

Turbine

History

Types of turbines

Resources

A turbine is any of various rotary machines that convert the kinetic energy in a stream of fluid (gas or liquid) into mechanical energy by passing the stream through a system of fixed and moving fans or blades. Turbines are simple but powerful machines that embody Newtons third law of motion which states that for every action there is an equal and opposite reaction. They are classified according to the driving fluid they use: steam, gas, water, and wind. Today, different types of turbines generate electricity, power ships and submarines, and propel jet aircraft.

History

the idea of using naturally moving water or air to help do work is an ancient one. Waterwheels and windmills are the best examples of ancient mankinds ability to

capture some of natures energy and put it to work. The Romans were grinding corn with a waterwheel as early as 70 BC, and modern-type windmills were being used in Persia around 700 AD. Both are ancestors of the turbine. Both have large surfaces (paddles, buckets, or a sail) at their wheel edges that are struck by moving wind or water which forces the wheel to turn. It was through the turning of this large central wheel, which could turn other smaller wheels, that mechanical energy was obtained and work, like grinding corn or operating a pump, could be accomplished.

The most ancient of these methods was the undershot wheel or paddle wheel. On these old waterwheels, only the very lowest part of the wheel was submerged beneath a moving body of water, and the entire wheel was turned as the river flowed past it, pushing against its paddles. This was a prototype for what came to be called an impulse turbine, which is one that is driven by the force of a fluid directly striking it. The under-shot waterwheel was followed during medieval times by the overshot wheel. This first made its appearance in Germany around the middle of the twelveth century and became the prototype for the modern reaction turbine. Contrasted to the impulse turbine whose energy source is kinetic energy (something striking something else and giving it some of its energy), the energy source for an overshot wheel (or reaction turbine) is known as potential energy. This is because it is the weight of the water acting under gravity that is used to turn the wheel. Renaissance engineers studied the waterwheel and realized that the action of water on a wheel with blades would be much more effective if the entire wheel were somehow enclosed in a kind of chamber. They knew very well that only a small amount of the water pushing or falling on a wheel blade or paddle actually strikes it, and that much of the energy contained in the onrushing water is lost or never actually captured. Enclosing the wheel and channeling the water through this chamber would result in a machine of greater efficiency and power. They were hampered, however, by a lack of any theoretical understanding of hydraulics as well as by a lack of precision machine tools with which they could carefully build things. Both of these problems were resolved to some degree in the eighteenth century, and one of the earliest examples of a reaction turbine was built in 1750 by the German mathematician and naturalist Johann Andres von Segner (1704-1777). In his system, the moving water entered a cylindrical box containing the shaft of a runner or rotor and flowed out through tangential openings, acting with its weight on the inclined vanes of the wheel.

A really efficient water turbine was now within reach it appeared, and a prize was offered in France by the Societe dEncouragement pour lIndustrie Nationale. The prize was won by the French mining engineer Claude Burdin (1778-1873), who published his results in 1828. It was in this publication that Burdin coined the word turbine which he took from the Latin turbo meaning a whirling or spinning top. It was Burdins student, Benoit Fourneyron (1801-1867), who improved and developed his mentors work and who is considered to be the inventor of the modern hydraulic turbine. Fourneyron built a six-horsepower turbine and later went on to build larger machines that worked under higher pressures and delivered more horsepower. His main contribution was his addition of a distributor which guided the water flow so that it acted with the greatest efficiency on the blades of the wheel. His was a reaction type turbine, since water entering through the vanes of the distributor (that was fitted inside the blades) then acted on the blades of the wheel.

Following Fourneyrons first turbine, which happened to be a hydraulic or water turbine, other turbines were developed that used the energy of a different material like gas or steam. Although these different types of turbines have different means of operation and certainly different histories, they still embody the basic characteristics of a turbine. They all spin, or receive their energy from some form of a moving fluid, and they all convert it into mechanical energy.

Types of turbines

While turbines can be classed as either impulse or reaction according to the way they function, there are four broad types of turbines categorized according to the fluid that supplies the driving force: steam, gas, water, or wind. Steam, water, and wind turbines are all used to generate electricity, and gas turbines are most often used by jet aircraft for propulsion. The steam turbine is mainly used by power plants that burn either fossil fuels or use nuclear energy to drive generators for consumer electricity. Steam turbines also power submarines and ships. The water or hydraulic turbine is used almost exclusively in hydroelectric plants to power an electric generator which then produces electric power for homes, offices, and factories. Wind turbines are the least common, but Scotland now uses the vertical machines called Darrieus turbines whose giant, bow-shaped blades look like huge egg beaters to generate electricity via the wind. The gas turbine is primarily used by jet aircraft.

Steam turbines transform the thermal energy stored in steam into mechanical work. The earliest steam turbine was also the earliest known steam engine. During the first century AD, the Greek mathematician and engineer, Hero of Alexandria, built what was basically a novelty and produced no useful work, but was nonetheless the first steam turbine. It consisted of a small, hollow sphere with two nozzles or bent tubes sticking out of it. The sphere was attached to a boiler which produced steam. As the steam escaped from the spheres hollow tubes, the sphere itself would rotate on its axis and continue to whirl. This was in principle a reaction steam turbine because the force of the escaping steam itself provided the thrust to make it spin. Steam was not considered in any type of turbine context again until the Italian Giovanni Branca published a work in 1629, in which he suggested the principle of the impulse steam turbine. In his book he details that it would be simple to convert the linear motion of a cylinder into the rotary motion needed for work by directing a jet of steam onto the vanes of a wheel, like water against a water-wheel. It is not known if he ever built such an engine.

Despite the advances made in understanding and managing steam that were gained in the eighteenth century, the steam turbine could not be built until the precision and strength of machining and materials had reached a certain level. In 1884, English engineer Charles Algernon Parsons (1854-1931) produced the first practical steam turbine engine. Although designed for the production of electric power, it was soon applied to marine propulsion and drove a ship named Turbinia in 1887. The spectacular speed and performance of this great ship opened a new era of steam propulsion at sea. Parsons overcame several major engineering difficulties involving stress, vibration, and balancing and truly deserves the title of father of the modern steam turbine. Besides their use at sea, steam turbines went on to generate an overwhelming proportion of the electricity used in the twentieth century. Today, the bulk of our electricity is generated by power stations using steam turbines. The steam is produced by the burning of fossil fuels (coal or gas) or by the use of nuclear energy. Most agree that steam turbines are still evolving and will play a considerable role in the generation of electrical power for some time to come.

Water or hydraulic turbines are identified with dams and the generation of hydroelectric power. When a turbine is operated by rapidly flowing or falling water, it is called an impulse turbine. The huge hydro-electric plant at Niagara Falls that was built at the end of the nineteenth century is this type of turbine. Water conditions usually determine what type of turbine is needed, and impulse water turbines require a constant flow of water to operate efficiently. Two aspects of this water flow is critical, its volume and its head. Water head is the distance water must fall before it strikes the turbines wheel. With a sufficient volume and head like Niagara, the impulse turbine can have its wheel or rotor mounted on either a vertical or a horizontal shaft. The ends of the turbines blades act like cup-shaped buckets, and as the water is directed at them at very high speeds by jets, the blades turn. As might be expected, most hydraulic turbines are of the reaction type since they are best suited to low-head situations. Here, the turbine is underwater and is turned by both the weight and speed of its flow. Its shaft is vertical and has either spirally curved blades or ones that resemble a ships propeller. Unlike impulse turbines which achieve rotation by the acceleration of water from the supply nozzles, reaction turbines work because of the acceleration of water in the rotor or runner. Both then transform the energy from the rushing water into mechanical energy.

Wind turbines are the least common or significant of all turbine types, and many technical texts do not even mention them. Unlike waterwheels which directly led to the hydraulic turbine, the windmill has for the most part not evolved as a significant source of modern energy. As with the noted Darrieus turbines in Scotland however, wind turbines do exist and have proved useful in areas of high, continuous winds. Wind turbine clusters generate electricity in the

KEY TERMS

Hydroelectric power Electric power derived from generators that are driven by hydraulic or water turbine engines.

Impulse turbine The force of a fastmoving fluid striking the blades that makes the rotor spin.

Kinetic energy That part of the energy of a body that it possesses as a result of its motion.

Mechanical energy Energy in the form of mechanical power.

Reaction turbine The rotor turns primarily as a result of the weight or pressure of a fluid on the blades.

Tehachapi Mountains near Barstow, California, as well as in certain areas of Hawaii and New Hampshire.

The best-known use for gas turbines is for jet engines. Gas turbines utilize hot gases as their names implies, and they are the newest type of turbine engine. Their gases are produced by the burning of some type of fuel, like kerosene. Air is then drawn into the front of the turbine and passed through a compressor where the compressed air is mixed with fuel in a combustion chamber and is burned. This produces hot gases that expand and therefore rush through the turbine rotors, causing them to spin. This spinning can be used to power an electric generator or a pump, but in the case of a jet aircraft, the hot expanding gases are sent out at very high speed from the rear nozzle of the engine, producing thrust which then pushes the engine and the aircraft forward. Gas turbines attain temperatures higher than those of a steam turbine (the hotter a gas turbine is, the more efficiently it runs) and consequently cannot be built with ordinary metals.

Turbine engines are an example of an idea that could not be put into practice until technology had accomplished certain advances. Probably the most important technical advance was the widespread introduction of steel and its alloys that occurred during the second half of the nineteenth century. The popularity and use of certain types of turbine engines rises and falls as needs, priorities, and situations change. A good example is the use of steam turbines for ship propulsion. After dominating sea travel for many years, steam turbines declined after the 1973 oil embargo because the fuel to make steam became prohibitively expensive. Diesels moved in to take their place since they required less fuel. Diesels can only use liquid fuel however, and as oil becomes scarcer in the next century, steam turbines for ships may again be the choice, since they can be driven by coal-burning boilers.

See also Alternative energy sources; Jet engine.

Resources

BOOKS

Meriam, J.L., and L.G. Kraige. Engineering Mechanics, Dynamics. 5th ed. New York: John Wiley & Sons, 2002.

Leonard C. Bruno

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Turbine

Turbine

A turbine is any of various rotary machines that convert the kinetic energy in a stream of fluid (gas or liquid) into mechanical energy by passing the stream through a system of fixed and moving fans or blades. Turbines are simple but powerful machines that embody Newton's third law of motion which states that for every action there is an equal and opposite reaction. They are classified according to the driving fluid they use: steam, gas, water , and wind . Today, different types of turbines generate electricity , power ships and submarines, and propel jet aircraft .


History

The idea of using naturally moving water or air to help do work is an ancient one. Waterwheels and windmills are the best examples of ancient mankind's ability to capture some of nature's energy and put it to work. The Romans were grinding corn with a waterwheel as early as 70 b.c., and modern-type windmills were being used in Persia around a.d. 700. Both are ancestors of the turbine. Both have large surfaces (paddles, buckets, or a sail) at their wheel edges that are struck by moving wind or water which forces the wheel to turn. It was through the turning of this large central wheel, which could turn other smaller wheels, that mechanical energy was obtained and work, like grinding corn or operating a pump, could be accomplished.

The most ancient of these methods was the undershot wheel or paddle wheel. On these old waterwheels, only the very lowest part of the wheel was submerged beneath a moving body of water, and the entire wheel was turned as the river flowed past it, pushing against its paddles. This was a prototype for what came to be called an impulse turbine, which is one that is driven by the force of a fluid directly striking it. The undershot waterwheel was followed during medieval times by the overshot wheel. This first made its appearance in Germany around the middle of the twelveth century and became the prototype for the modern reaction turbine. Contrasted to the impulse turbine whose energy source is kinetic energy (something striking something else and giving it some of its energy), the energy source for an overshot wheel (or reaction turbine) is known as potential energy. This is because it is the weight of the water acting under gravity that is used to turn the wheel. Renaissance engineers studied the waterwheel and realized that the action of water on a wheel with blades would be much more effective if the entire wheel were somehow enclosed in a kind of chamber. They knew very well that only a small amount of the water pushing or falling on a wheel blade or paddle actually strikes it, and that much of the energy contained in the onrushing water is lost or never actually captured. Enclosing the wheel and channeling the water through this chamber would result in a machine of greater efficiency and power. They were hampered, however, by a lack of any theoretical understanding of hydraulics as well as by a lack of precision machine tools with which they could carefully build things. Both of these problems were resolved to some degree in the eighteenth century, and one of the earliest examples of a reaction turbine was built in 1750 by the German mathematician and naturalist Johann Andres von Segner (1704-1777). In his system, the moving water entered a cylindrical box containing the shaft of a runner or rotor and flowed out through tangential openings, acting with its weight on the inclined vanes of the wheel.

A really efficient water turbine was now within reach it appeared, and a prize was offered in France by the Societe d'Encouragement pour l'Industrie Nationale. The prize was won by the French mining engineer Claude Burdin (1778-1873), who published his results in 1828. It was in this publication that Burdin coined the word "turbine" which he took from the Latin "turbo" meaning a whirling or spinning top. It was Burdin's student, Benoit Fourneyron (1801-1867), who improved and developed his master's work and who is considered to be the inventor of the modern hydraulic turbine. Four-neyron built a six-horsepower turbine and later went on to build larger machines that worked under higher pressures and delivered more horsepower. His main contribution was his addition of a distributor which guided the water flow so that it acted with the greatest efficiency on the blades of the wheel. His was a reaction type turbine, since water entering through the vanes of the distributor (that was fitted inside the blades) then acted on the blades of the wheel. Following Fourneyron's first turbine, which happened to be a hydraulic or water turbine, other turbines were developed that used the energy of a different material like gas or steam. Although these different types of turbines have different means of operation and certainly different histories, they still embody the basic characteristics of a turbine. They all spin, or receive their energy from some form of a moving fluid, and they all convert it into mechanical energy.

Types of turbines

While turbines can be classed as either impulse or reaction according to the way they function, there are four broad types of turbines categorized according to the fluid that supplies the driving force: steam, gas, water, or wind. Steam, water, and wind turbines are all used to generate electricity, and gas turbines are most often used by jet aircraft for propulsion. The steam turbine is mainly used by power plants that burn either fossil fuels or use nuclear energy to drive generators for consumer electricity. Steam turbines also power submarines and ships. The water or hydraulic turbine is used almost exclusively in hydroelectric plants to power an electric generator which then produces electric power for homes, offices, and factories. Wind turbines are the least common, but Scotland now uses the vertical machines called Darrieus turbines whose giant, bow-shaped blades look like huge egg beaters to generate electricity via the wind. The gas turbine is primarily used by jet aircraft.

Steam turbines transform the thermal energy stored in steam into mechanical work. The earliest steam turbine was also the earliest known steam engine . During the first century a.d., the Greek mathematician and engineer, Hero of Alexandria, built what was basically a novelty and produced no useful work, but was nonetheless the first steam turbine. It consisted of a small, hollow sphere with two nozzles or bent tubes sticking out of it. The sphere was attached to a boiler which produced steam. As the steam escaped from the sphere's hollow tubes, the sphere itself would rotate on its axis and continue to whirl. This was in principle a reaction steam turbine because the force of the escaping steam itself provided the thrust to make it spin. Steam was not considered in any type of turbine context again until the Italian Giovanni Branca published a work in 1629, in which he suggested the principle of the impulse steam turbine. In his book he details that it would be simple to convert the linear motion of a cylinder into the rotary motion needed for work by directing a jet of steam onto the vanes of a wheel, like water against a waterwheel. It is not known if he ever built such an engine.

Despite the advances made in understanding and managing steam that were gained in the eighteenth century, the steam turbine could not be built until the precision and strength of machining and materials had reached a certain level. In 1884, English engineer Charles Algernon Parsons (1854-1931) produced the first practical steam turbine engine. Although designed for the production of electric power, it was soon applied to marine propulsion and drove a ship named Turbinia in 1887. The spectacular speed and performance of this great ship opened a new era of steam propulsion at sea. Parsons overcame several major engineering difficulties involving stress, vibration, and balancing and truly deserves the title of father of the modern steam turbine. Besides their use at sea, steam turbines went on to generate an overwhelming proportion of the electricity used in the twentieth century. Today, the bulk of our electricity is generated by power stations using steam turbines. The steam is produced by the burning of fossil fuels (coal or gas) or by the use of nuclear energy. Most agree that steam turbines are still evolving and will play a considerable role in the generation of electrical power for some time to come.

Water or hydraulic turbines are identified with dams and the generation of hydroelectric power. When a turbine is operated by rapidly flowing or falling water, it is called an impulse turbine. The huge hydro-electric plant at Niagara Falls that was built at the end of the nineteenth century is this type of turbine. Water conditions usually determine what type of turbine is needed, and impulse water turbines require a constant flow of water to operate efficiently. Two aspects of this water flow is critical, its volume and its head. Water head is the distance water must fall before it strikes the turbine's wheel. With a sufficient volume and head like Niagara, the impulse turbine can have its wheel or rotor mounted on either a vertical or a horizontal shaft. The ends of the turbine's blades act like cup-shaped buckets, and as the water is directed at them at very high speeds by jets, the blades turn. As might be expected, most hydraulic turbines are of the reaction type since they are best suited to low-head situations. Here, the turbine is underwater and is turned by both the weight and speed of its flow. Its shaft is vertical and has either spirally curved blades or ones that resemble a ship's propeller. Unlike impulse turbines which achieve rotation by the acceleration of water from the supply nozzles, reaction turbines work because of the acceleration of water in the rotor or runner. Both then transform the energy from the rushing water into mechanical energy.

Wind turbines are the least common or significant of all turbine types, and many technical texts do not even mention them. Unlike waterwheels which directly led to the hydraulic turbine, the windmill has for the most part not evolved as a significant source of modern energy. As with the noted Darrieus turbines in Scotland however, wind turbines do exist and have proved useful in areas of high, continuous winds. Wind turbine clusters generate electricity in the Tehachapi Mountains near Barstow, California, as well as in certain areas of Hawaii and New Hampshire.

The best-known use for gas turbines is for jet engines. Gas turbines utilize hot gases as their names implies, and they are the newest type of turbine engine. Their gases are produced by the burning of some type of fuel, like kerosene. Air is then drawn into the front of the

turbine and passed through a compressor where the compressed air is mixed with fuel in a combustion chamber and is burned. This produces hot gases that expand and therefore rush through the turbine rotors, causing them to spin. This spinning can be used to power an electric generator or a pump, but in the case of a jet aircraft, the hot expanding gases are sent out at very high speed from the rear nozzle of the engine, producing thrust which then pushes the engine and the aircraft forward. Gas turbines attain temperatures higher than those of a steam turbine (the hotter a gas turbine is, the more efficiently it runs) and consequently cannot be built with ordinary metals.

Turbine engines are an example of an idea that could not be put into practice until technology had accomplished certain advances. Probably the most important technical advance was the widespread introduction of steel and its alloys that occurred during the second half of the nineteenth century. The popularity and use of certain types of turbine engines rises and falls as needs, priorities, and situations change. A good example is the use of steam turbines for ship propulsion. After dominating sea travel for many years, steam turbines declined after the 1973 oil embargo because the fuel to make steam became prohibitively expensive. Diesels moved in to take their place since they required less fuel. Diesels can only use liquid fuel however, and as oil becomes scarcer in the next century, steam turbines for ships may again be the choice, since they can be driven by coal-burning boilers.

See also Alternative energy sources; Jet engine.


Resources

books

Gunston, Bill. The Development of Jet and Turbine Aero Engines. 2nd ed. New York: Haynes Publishing, 1998.

IEEE Guide for the Operation and Maintenance of TurbineGenerators. Institute of Electrical and Electronics Engineers, 1990.

Meriam, J.L., and L.G. Kraige. Engineering Mechanics, Dynamics. 5th ed. New York: John Wiley & Sons, 2002.


Leonard C. Bruno

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hydroelectric power

Electric power derived from generators that are driven by hydraulic or water turbine engines.

Impulse turbine

—The force of a fastmoving fluid striking the blades that makes the rotor spin.

Kinetic energy

—That part of the energy of a body that it possesses as a result of its motion.

Mechanical energy

—Energy in the form of mechanical power.

Reaction turbine

—The rotor turns primarily as a result of the weight or pressure of a fluid on the blades.

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