A turbine is a rotary engine that extracts energy from a fluid flow. An engine is a mechanical device that produces some form of output from a given input In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός FLUID ( F ast L ight '''U'''ser '''I'''nterface D esigner is a graphical editor that is used to produce FLTK Source code Claude Burdin (1788-1873) coined the term from the Latin turbo, or vortex, during an 1828 engineering competition. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. V erification of the O rigins of R otation in T ornadoes Ex periment or VORTEX, is a field project that seeks to understand how a Benoit Fourneyron (1802-1867), a student of Claude Burdin, built the first practical water turbine. Benoît Fourneyron ( October 31, 1802 &ndash July 31, 1867) was a French Engineer, born in Saint-Étienne.

The simplest turbines have one moving part, a rotor assembly, which is a shaft with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they rotate and impart energy to the rotor. Early turbine examples are windmills and water wheels. A windmill is a machine that is powered by the energy of the wind A water wheel is a means of extracting power from the flow (or fall of water otherwise known as Hydropower.

Gas, steam, and water turbines have a casing around the blades that contains and controls the working fluid. A gas turbine, also called a combustion turbine, is a rotary Engine that extracts energy from a flow of Combustion gas A steam turbine is a mechanical device that extracts Thermal energy from pressurized Steam, and converts it into useful mechanical work A water turbine is a rotary Engine that takes energy from moving water Credit for invention of the modern steam turbine is given to British Engineer Sir Charles Parsons (1854 - 1931). Sir Charles Algernon Parsons, OM (13 June 1854 &ndash 11 February 1931 was a British Engineer, best known for his invention of the Steam turbine.

A device similar to a turbine but operating in reverse is a compressor or pump. A gas compressor is a mechanical device that increases the Pressure of a Gas by reducing its Volume. For information on Wikipedia project-related discussions see WikipediaVillage pump. The axial compressor in many gas turbine engines is a common example. Axial compressors are rotating aerofoil based compressors in which the working fluid principally flows parallel to the axis of rotation A gas turbine, also called a combustion turbine, is a rotary Engine that extracts energy from a flow of Combustion gas

Contents 1 Theory of operation 2 Types of turbines 2.1 Other 3 Uses of turbines 4 Shrouded tidal turbines 5 See also 6 Notes 7 External links

Theory of operation

A working fluid contains potential energy (pressure head) and kinetic energy (velocity head). Potential energy can be thought of as Energy stored within a physical system Hydraulic head is a specific measurement of water pressure or Total energy per Unit weight above a Geodetic datum. The kinetic energy of an object is the extra Energy which it possesses due to its motion The fluid may be compressible or incompressible. In Thermodynamics and Fluid mechanics, compressibility is a measure of the relative volume change of a Fluid or Solid as a response Fluid mechanics is the study of how Fluids move and the Forces on them Several physical principles are employed by turbines to collect this energy:

Impulse turbines 

These turbines change the direction of flow of a high velocity fluid jet. In Classical mechanics, an impulse is defined as the Integral of a Force with respect to Time: \mathbf{I} = \int \mathbf{F}\ The resulting impulse spins the turbine and leaves the fluid flow with diminished kinetic energy. There is no pressure change of the fluid in the turbine rotor blades. Before reaching the turbine the fluid's pressure head is changed to velocity head by accelerating the fluid with a nozzle. A nozzle is a mechanical device or Orifice designed to control the characteristics of a Fluid flow as it exits (or enters an enclosed chamber or Pipe. Pelton wheels and de Laval turbines use this process exclusively. The Pelton wheel is among the most efficient types of Water turbines. A steam turbine is a mechanical device that extracts Thermal energy from pressurized Steam, and converts it into useful mechanical work Impulse turbines do not require a pressure casement around the runner since the fluid jet is prepared by a nozzle prior to reaching turbine. Newton's second law describes the transfer of energy for impulse turbines. Newton's laws of motion are three Physical laws which provide relationships between the Forces acting on a body and the motion of the

Reaction turbines 

These turbines develop torque by reacting to the fluid's pressure or weight. In Classical mechanics, Newton's third law states that Forces occur in pairs one called the Action and the other the Reaction ( actio et A torque (τ in Physics, also called a moment (of force is a pseudo- vector that measures the tendency of a force to rotate an object about The pressure of the fluid changes as it passes through the turbine rotor blades. A pressure casement is needed to contain the working fluid as it acts on the turbine stage(s) or the turbine must be fully immersed in the fluid flow (wind turbines). The casing contains and directs the working fluid and, for water turbines, maintains the suction imparted by the draft tube. Francis turbines and most steam turbines use this concept. The Francis turbine is a type of Water turbine that was developed by James B A steam turbine is a mechanical device that extracts Thermal energy from pressurized Steam, and converts it into useful mechanical work For compressible working fluids, multiple turbine stages may be used to harness the expanding gas efficiently. Newton's third law describes the transfer of energy for reaction turbines. Newton's laws of motion are three Physical laws which provide relationships between the Forces acting on a body and the motion of the

Turbine designs will use both these concepts to varying degrees whenever possible. Wind turbines use an airfoil to generate lift from the moving fluid and impart it to the rotor (this is a form of reaction). A wind turbine is a rotating machine which converts the Kinetic energy in Wind into Mechanical energy. An airfoil (in American English) or aerofoil (in British English) is the shape of a Wing or blade (of a Propeller, rotor In the context of a Fluid flow relative to a body the lift force is the component of the Aerodynamic force that is Perpendicular to the flow Wind turbines also gain some energy from the impulse of the wind, by deflecting it at an angle. Crossflow turbines are designed as an impulse machine, with a nozzle, but in low head applications maintain some efficiency through reaction, like a traditional water wheel. A Crossflow turbine, Banki-Michell turbine, or Ossberger turbine is a Water turbine developed by the Australian Anthony Michell, the Hungarian Turbines with multiple stages may utilize either reaction or impulse blading at high pressure. Steam Turbines were traditionally more impulse but continue to move towards reaction designs similar to those used in Gas Turbines. At low pressure the operating fluid medium expands in volume for small reductions in pressure. Under these conditions (termed Low Pressure Turbines) blading becomes strictly a reaction type design with the base of the blade solely impulse. The reason is due to the effect of the rotation speed for each blade. As the volume increases, the blade height increases, and the base of the blade spins at a slower speed relative to the tip. This change in speed forces a designer to change from impulse at the base, to a high reaction style tip.

Classical turbine design methods were developed in the mid 19th century. Vector analysis related the fluid flow with turbine shape and rotation. Graphical calculation methods were used at first. Formulas for the basic dimensions of turbine parts are well documented and a highly efficient machine can be reliably designed for any fluid flow condition. Some of the calculations are empirical or 'rule of thumb' formulae, and others are based on classical mechanics. Classical mechanics is used for describing the motion of Macroscopic objects from Projectiles to parts of Machinery, as well as Astronomical objects As with most engineering calculations, simplifying assumptions were made.

Velocity triangles can be used to calculate the basic performance of a turbine stage. Gas exits the stationary turbine nozzle guide vanes at absolute velocity V_a1. The rotor rotates at velocity U. Relative to the rotor, the velocity of the gas as it impinges on the rotor entrance is V_r1. The gas is turned by the rotor and exits, relative to the rotor, at velocity V_r2. However, in absolute terms the rotor exit velocity is V_a2. The velocity triangles are constructed using these various velocity vectors. Velocity triangles can be constructed at any section through the blading (for example: hub , tip, midsection and so on) but are usually shown at the mean stage radius. Mean performance for the stage can be calculated from the velocity triangles, at this radius, using the Euler equation:

Whence:

where:

specific enthalpy drop across stage

turbine entry total (or stagnation) temperature

turbine rotor peripheral velocity

change in whirl velocity

The turbine pressure ratio is a function of and the turbine efficiency.

Modern turbine design carries the calculations further. Computational fluid dynamics dispenses with many of the simplifying assumptions used to derive classical formulas and computer software facilitates optimization. Computational fluid dynamics (CFD is one of the branches of Fluid mechanics that uses Numerical methods and algorithms to solve and analyze problems that involve These tools have led to steady improvements in turbine design over the last forty years.

The primary numerical classification of a turbine is its specific speed. This number describes the speed of the turbine at its maximum efficiency with respect to the power and flow rate. The specific speed is derived to be independent of turbine size. Given the fluid flow conditions and the desired shaft output speed, the specific speed can be calculated and an appropriate turbine design selected.

The specific speed, along with some fundamental formulas can be used to reliably scale an existing design of known performance to a new size with corresponding performance.

Off-design performance is normally displayed as a turbine map or characteristic. Each Turbine in a Gas turbine engine has an operating map Complete maps are either based on turbine rig test results or are predicted by a special computer program

Types of turbines

• Steam turbines are used for the generation of electricity in thermal power plants, such as plants using coal or fuel oil or nuclear power. A steam turbine is a mechanical device that extracts Thermal energy from pressurized Steam, and converts it into useful mechanical work A power station (also referred to as generating station, power plant or powerhouse) is an industrial facility for the generation of Fuel oil is a fraction obtained from Petroleum Distillation, either as a distillate or a residue Nuclear power is any Nuclear technology designed to extract usable Energy from atomic nuclei via controlled Nuclear reactions They were once used to directly drive mechanical devices such as ship's propellors (eg the Turbinia), but most such applications now use reduction gears or an intermediate electrical step, where the turbine is used to generate electricity, which then powers an electric motor connected to the mechanical load. A propeller is essentially a type of fan which transmits power by converting Rotational motion into Thrust for propulsion of a vehicle such as an Development Charles Algernon Parsons invented the steam turbine in 1884 and having foreseen its potential to power ships he set up the Marine Steam Turbine Company An electric motor uses Electrical energy to produce Mechanical energy.
• Gas turbines are sometimes referred to as turbine engines. A gas turbine, also called a combustion turbine, is a rotary Engine that extracts energy from a flow of Combustion gas Such engines usually feature an inlet, fan, compressor, combustor and nozzle (possibly other assemblies) in addition to one or more turbines.
• Transonic turbine. Transonic is an Aeronautics term referring to a range of velocities just below and above the Speed of sound (about mach 0 The gasflow in most turbines employed in gas turbine engines remains subsonic throughout the expansion process. In a transonic turbine the gasflow becomes supersonic as it exits the nozzle guide vanes, although the downstream velocities normally become subsonic. Transonic turbines operate at a higher pressure ratio than normal but are usually less efficient and uncommon. This turbine works well in creating power from water.
• Contra-rotating turbines. Contra-rotating, also referred to as coaxial contra-rotating, is a technique whereby Propellers or fan blades mounted on a common axle rotate in opposite directions Some efficiency advantage can be obtained if a downstream turbine rotates in the opposite direction to an upstream unit. However, the complication may be counter-productive.
• Statorless turbine Multi-stage turbines have a set of static (meaning stationary) inlet guide vanes that direct the gasflow onto the rotating rotor blades. The stator is the stationary part of an Electric generator or Electric motor. In a statorless turbine the gasflow exiting an upstream rotor impinges onto a downstream rotor without an intermediate set of stator vanes (that rearrange the pressure/velocity energy levels of the flow) being encountered.
• Ceramic turbine. The word ceramic is derived from the Greek word κεραμικός ( keramikos) Conventional high-pressure turbine blades (and vanes) are made from nickel-steel alloys and often utilise intricate internal air-cooling passages to prevent the metal from melting. In recent years, experimental ceramic blades have been manufactured and tested in gas turbines, with a view to increasing Rotor Inlet Temperatures and/or, possibly, eliminating aircooling. Ceramic blades are more brittle than their metallic counterparts, and carry a greater risk of catastrophic blade failure.
• Shrouded turbine. A ducted fan is a propulsion arrangement whereby a fan which is a type of Propeller, is mounted within a cylindrical shroud or duct Many turbine rotor blades have a shroud at the top, which interlocks with that of adjacent blades, to increase damping and thereby reduce blade flutter.
• Shroudless turbine. A ducted fan is a propulsion arrangement whereby a fan which is a type of Propeller, is mounted within a cylindrical shroud or duct Modern practise is, where possible, to eliminate the rotor shroud, thus reducing the centrifugal load on the blade and the cooling requirements. Shroud usually refers to an item such as a cloth that covers or protects some other object
• Bladeless turbine uses the boundary layer effect and not a fluid impinging upon the blades as in a conventional turbine. The Tesla turbine is a bladeless centrifugal flow Turbine expander patented by Nikola Tesla in 1913
• Water turbines
  • Pelton turbine, a type of impulse water turbine. A water turbine is a rotary Engine that takes energy from moving water The Pelton wheel is among the most efficient types of Water turbines.
  • Francis turbine, a type of widely used water turbine. The Francis turbine is a type of Water turbine that was developed by James B
  • Kaplan turbine, a variation of the Francis Turbine. The Kaplan turbine is a propeller-type Water turbine that has adjustable blades
• Wind turbine. A wind turbine is a rotating machine which converts the Kinetic energy in Wind into Mechanical energy. These normally operate as a single stage without nozzle and interstage guide vanes. An exception is the Éolienne Bollée, which has a stator and a rotor, thus being a true turbine. Éolienne Bollée is an unusual Wind turbine, unique for having a stator and a rotor as a Water turbine has

Other

• Velocity compound "Curtis". Curtis combined the de Laval and Parsons turbine by using a set of fixed nozzles on the first stage or stator and then a rank of fixed and rotating stators as in the Parsons, typically up to ten compared with up to a hundred stages, however the efficiency of the turbine was less than that of the Parsons but it operated at much lower speeds and at lower pressures which made it ideal for ships. Note that the use of a small section of a Curtis, typically one nozzle section and two rotors is termed a "Curtis Wheel"
• Pressure Compund Multistage Impulse or Rateau. The Rateau employs simple Impulse rotors separated by a nozzle diaphragm. The diaphragm is essentially a partition wall in the turbine with a series of tunnels cut into it, funnel shaped with the broad end facing the previous stage and the narrow the next they are also angled to direct the steam jets onto the impulse rotor.

Uses of turbines

Almost all electrical power on Earth is produced with a turbine of some type. Very high efficiency turbines harness about 40% of the thermal energy, with the rest exhausted as waste heat.

Most jet engines rely on turbines to supply mechanical work from their working fluid and fuel as do all nuclear ships and power plants. specific --->A jet engine is a Reaction engine that discharges a fast moving jet of Fluid to

Turbines are often part of a larger machine. A gas turbine, for example, may refer to an internal combustion machine that contains a turbine, ducts, compressor, combustor, heat-exchanger, fan and (in the case of one designed to produce electricity) an alternator. A gas turbine, also called a combustion turbine, is a rotary Engine that extracts energy from a flow of Combustion gas However, it must be noted that the collective machine referred to as the turbine in these cases is designed to transfer energy from a fuel to the fluid passing through such an internal combustion device as a means of propulsion, and not to transfer energy from the fluid passing through the turbine to the turbine as is the case in turbines used for electricity provision etc.

Reciprocating piston engines such as aircraft engines can use a turbine powered by their exhaust to drive an intake-air compressor, a configuration known as a turbocharger (turbine supercharger) or, colloquially, a "turbo". An aircraft engine is a Propulsion system for an Aircraft. Aircraft engines are almost always a type of lightweight Internal combustion engine. A turbocharger, or turbo, is an air Compressor used for forced-induction of an Internal combustion engine. A supercharger is an air compressor used for Forced induction of an Internal combustion engine.

Turbines can have very high power density (ie the ratio of power to weight, or power to volume). This is because of their ability to operate at very high speeds. The Space Shuttle's main engines use turbopumps (machines consisting of a pump driven by a turbine engine) to feed the propellants (liquid oxygen and liquid hydrogen) into the engine's combustion chamber. NASA 's Space Shuttle, officially called the Space Transportation System ( STS) is the Spacecraft currently used by the United States As the name suggests a turbopump comprises basically two main components a rotodynamic Pump and a driving Turbine, both mounted on the same shaft The liquid hydrogen turbopump is slightly larger than an automobile engine (weighing approximately 700 lb) and produces nearly 70,000 hp (52. 2 MW). The watt (symbol W) is the SI derived unit of power, equal to one Joule of energy per Second.

Turboexpanders are widely used as sources of refrigeration in industrial processes. A turboexpander, also referred to as a turbo-expander or an expansion turbine, is a centrifugal or axial flow Turbine through which a high Pressure

Turbines could also be used as powering system for a remote controlled plane that creates thrust and lifts the plane of the ground. They come in different sizes and could be as small as soda can, still be strong enough to move objects with a weight of 100kg.

Shrouded tidal turbines

An emerging renewable energy technology is the shrouded tidal turbine enclosed in a venturi shaped shroud or duct producing a sub atmosphere of low pressure behind the turbine, allowing the turbine to operate at higher efficiency (than the Betz limit ^[1] of 59. The Venturi effect is the fluid pressure that results when an incompressible fluid flows through a constricted section of pipe Wind turbines are designed to exploit the wind energy that exists at a location 3%) and typically 3 times higher power output ^[2] than a turbine of the same size in free stream.

As shown in the CFD generated figure^[3], it can be seen that a down stream low pressure (shown by the gradient lines) draws upstream flow into the inlet of the shroud from well outside the inlet of the shroud. Computational fluid dynamics (CFD is one of the branches of Fluid mechanics that uses Numerical methods and algorithms to solve and analyze problems that involve This flow is drawn into the shroud and concentrated (as seen by the red coloured zone). This augmentation of flow velocity corresponds to a 3-4 times increase in energy available to the turbine. Therefore a turbine located in the throat of the shroud is then able to achieve higher efficiency, and an output 3-4 times the energy the turbine would be capable of if it were in open or free stream. For this reason shrouded turbines are not subject to the properties of the Betz limit.

Considerable commercial interest has been shown in recent times in shrouded tidal turbines as it allows a smaller turbine to be used at sites where large turbines are restricted. Arrayed across a seaway or in fast flowing rivers shrouded tidal turbines are easily cabled to a terrestrial base and connected to a grid or remote community. Alternatively the property of the shroud that produces an accelerated flow velocity across the turbine allows tidal flows formerly too slow for commercial use to be utilised for commercial energy production.

While the shroud may not be practical in wind, as a tidal turbine it is gaining more popularity and commercial use. A shrouded tidal turbine is mono directional and constantly needs to face upstream in order to operate. It can be floated under a pontoon on a swing mooring, fixed to the seabed on a mono pile and yawed like a wind sock to continually face upstream. A shroud can also be built into a tidal fence increasing the performance of the turbines.

Cabled to the mainland they can be grid connected or can be scaled down to provide energy to remote communities where large civil infrastructures are not viable. Similarly to tidal stream open turbines they have little if any environmental or visual amenity impact.

See also

• Rotordynamics
• Turbo-alternator
• Turbinia
• RMS Lusitania
• Secondary flow in turbines

Notes

External links

• Turbine introductory math
• Turbines jet powered 1/16 scale Airbus A330
• Turbine working process

Rotordynamics is a specialized branch of Applied mechanics concerned with the behavior and diagnosis of rotating structures alternator is an electromechanical device that converts mechanical energy to Alternating current electrical energy Development Charles Algernon Parsons invented the steam turbine in 1884 and having foreseen its potential to power ships he set up the Marine Steam Turbine Company Construction and trials Owned by the Cunard Steamship Company built by John Brown and Company Lusitania was named for the ancient Roman province of In Fluid dynamics, a secondary flow is a relatively minor flow superimposed on the primary flow where the primary flow usually matches very closely the flow pattern predicted

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