Turbo generator

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250 kW steam turbine generator set (1910) TMW 773 - Steam turbine generator set.jpg
250 kW steam turbine generator set (1910)
500 MW Siemens multi stage steam turbine with generator set (rear, red) Turbogenerator01.jpg
500 MW Siemens multi stage steam turbine with generator set (rear, red)
Parsons first 1 MW steam turbine driven "Turbogenerator" (made 1900 for a plant in Elberfeld, Germany) 1900 Elberfeld 1MW Generator.jpg
Parsons first 1 MW steam turbine driven "Turbogenerator" (made 1900 for a plant in Elberfeld, Germany)
Otto Blathy in the armature of a Ganz turbo generator (1904) Blathy in a Ganz turbogenerator.jpg
Ottó Bláthy in the armature of a Ganz turbo generator (1904)
Small RP4 steam turbo generator set 500W/24V for a steam locomotive: alternator (left) + turbine (right) Turbogenerator przekroj.jpg
Small RP4 steam turbo generator set 500W/24V for a steam locomotive: alternator (left) + turbine (right)

A turbo generator set or turbine generator set is the compound of a steam turbine or gas turbine shaft-connected to a fast running electric generator for the generation of electric power. Large steam-powered turbo generators provide the majority of the world's electricity and are also used by steam-powered turbo-electric ships. [1]

Contents

Small turbo-generators with gas turbines are often used as auxiliary power units (APU, mainly for aircraft). For base loads diesel generators or gas engines are usually preferred, since they offer better fuel efficiency; however, such stationary engines have a lower power density and are built only up to about 10 MW power per unit.

The efficiency of larger gas turbines (50 MW or more) can be enhanced by using a combined cycle, where the remaining energy of hot exhaust gases is used to generate steam which drives another steam turbine on the same shaft or a separate generator set.

History

Turbine contruction at the Ganz Company around 1886 Turbinaszereles.jpg
Turbine contruction at the Ganz Company around 1886

The first turbo-generators were water turbines which propelled electric generators. The first Hungarian water turbine was designed by the engineers of the Ganz Works in 1866; industrial-scale production with dynamo generators started only in 1883. [2] Engineer Charles Algernon Parsons demonstrated a DC steam-powered turbogenerator using a dynamo in 1887, [3] and by 1901 had supplied the first large industrial AC turbogenerator of megawatt power to a plant in Eberfeld, Germany. [4]

Turbo generators were also used on steam locomotives as a power source for coach lighting and water pumps for heating systems.

Construction features

Unlike hydraulic turbines which usually operate at lower speeds (100 to 600 rpm), the efficiency of a steam turbine is higher at higher speeds and therefore a turbo generator is used for steam turbines. The rotor of a turbo generator is a non-salient pole type usually with two poles. [5]

The normal speed of a turbo generator is 1500 or 3000 rpm with four or two poles at 50 Hz (1800 or 3600 rpm with four or two poles at 60 Hz). Salient rotors will be very noisy and with a lot of windage loss. The rotating parts of a turbo generator are subjected to high mechanical stresses because of the high operation speed. To make the rotor mechanically resistant in large turbo-alternators, the rotor is normally forged from solid steel and alloys like chromium-nickel-steel or chromium-nickel-molybdenum are used. The overhang of windings at the periphery will be secured by steel retaining rings. Heavy non-magnetic metal wedges on top of the slots hold the field windings against centrifugal forces. Hard composition insulating materials, like mica and asbestos, are normally used in the slots of rotor. These material can withstand high temperatures and high crushing forces. [6]

The stator of large turbo generators may be built of two or more parts while in smaller turbo-generators it is built up in one complete piece. [7]

Hydrogen-cooled turbo generator

Based on the air-cooled turbo generator, gaseous hydrogen first went into service as the coolant in a hydrogen-cooled turbo generator in October 1937, at the Dayton Power & Light Co. in Dayton, Ohio. [8] Hydrogen is used as the coolant in the rotor and sometimes the stator, allowing an increase in specific utilization and a 99.0% efficiency. Because of the high thermal conductivity, high specific heat and low density of hydrogen gas, this is the most common type in its field today. The hydrogen can be manufactured on-site by electrolysis.

The generator is hermetically sealed to prevent escape of the hydrogen gas. The absence of oxygen in the atmosphere within significantly reduces the damage of the windings' insulation by eventual corona discharges. The hydrogen gas is circulated within the rotor enclosure, and cooled by a gas-to-water heat exchanger. [9]

See also

Related Research Articles

Engine machine that converts one form of energy into mechanical energy

An engine or motor is a machine designed to convert one form of energy into mechanical energy. Heat engines convert heat into work via various thermodynamic processes. The internal combustion engine is perhaps the most common example of a heat engine, in which heat from the combustion of a fuel causes rapid pressurisation of the gaseous combustion products in the combustion chamber, causing them to expand and drive a piston, which turns a crankshaft. Electric motors convert electrical energy into mechanical motion, pneumatic motors use compressed air, and clockwork motors in wind-up toys use elastic energy. In biological systems, molecular motors, like myosins in muscles, use chemical energy to create forces and ultimately motion.

Steam turbine Machine that uses steam to rotate a shaft

A steam turbine is a device that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft. Its modern manifestation was invented by Charles Parsons in 1884.

Turbine Rotary mechanical device that extracts energy from a fluid flow

A turbine is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating electrical power when combined with a generator. A turbine is a turbomachine with at least one moving part called a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades so that they move and impart rotational energy to the rotor. Early turbine examples are windmills and waterwheels.

Gas turbine Type of internal combustion engine

A gas turbine, also called a combustion turbine, is a type of continuous and internal combustion engine. The main elements common to all gas turbine engines are:

Electric generator Device that converts other energy to electrical energy

In electricity generation, a generator is a device that converts motive power into electrical power for use in an external circuit. Sources of mechanical energy include steam turbines, gas turbines, water turbines, internal combustion engines, wind turbines and even hand cranks. The first electromagnetic generator, the Faraday disk, was invented in 1831 by British scientist Michael Faraday. Generators provide nearly all of the power for electric power grids.

Alternator Device converting mechanical to electrical energy

An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature. Occasionally, a linear alternator or a rotating armature with a stationary magnetic field is used. In principle, any AC electrical generator can be called an alternator, but usually the term refers to small rotating machines driven by automotive and other internal combustion engines.

Synchronous motor Type of AC motor

A synchronous electric motor is an AC motor in which, at steady state, the rotation of the shaft is synchronized with the frequency of the supply current; the rotation period is exactly equal to an integral number of AC cycles. Synchronous motors contain multiphase AC electromagnets on the stator of the motor that create a magnetic field which rotates in time with the oscillations of the line current. The rotor with permanent magnets or electromagnets turns in step with the stator field at the same rate and as a result, provides the second synchronized rotating magnet field of any AC motor. A synchronous motor is termed doubly fed if it is supplied with independently excited multiphase AC electromagnets on both the rotor and stator.

Combined cycle power plant

A combined cycle power plant is an assembly of heat engines that work in tandem from the same source of heat, converting it into mechanical energy. On land, when used to make electricity the most common type is called a combined cycle gas turbine (CCGT) plant. The same principle is also used for marine propulsion, where it is called a combined gas and steam (COGAS) plant. Combining two or more thermodynamic cycles improves overall efficiency, which reduces fuel costs.

Microturbines are 25 to 500 kilowatt gas turbines evolved from piston engine turbochargers, aircraft auxiliary power units (APU) or small jet engines, the size of a refrigerator. Early turbines of 30-70 kW grew to 200-250 kW.

Thermal power station

A thermal power station is a power station in which heat energy is converted to electricity. Typically, water is heated into steam, which is used to drive an electrical generator. After it passes through the turbine the steam is condensed in a steam condenser and recycled to where it was heated. This is known as a Rankine cycle. The greatest variation in the design of thermal power stations is due to the different heat sources: fossil fuel, nuclear energy, solar energy, biofuels, and waste incineration are all used. Certain thermal power stations are also designed to produce heat for industrial purposes, for district heating, or desalination of water, in addition to generating electrical power.

Doubly-fed electric machines also slip-ring generators are electric motors or electric generators, where both the field magnet windings and armature windings are separately connected to equipment outside the machine.

An induction generator or asynchronous generator is a type of alternating current (AC) electrical generator that uses the principles of induction motors to produce electric power. Induction generators operate by mechanically turning their rotors faster than synchronous speed. A regular AC induction motor usually can be used as a generator, without any internal modifications. Induction generators are useful in applications such as mini hydro power plants, wind turbines, or in reducing high-pressure gas streams to lower pressure, because they can recover energy with relatively simple controls.

In electrical engineering, electric machine is a general term for machines using electromagnetic forces, such as electric motors, electric generators, and others. They are electromechanical energy converters: an electric motor converts electricity to mechanical power while an electric generator converts mechanical power to electricity. The moving parts in a machine can be rotating or linear. Besides motors and generators, a third category often included is transformers, which although they do not have any moving parts are also energy converters, changing the voltage level of an alternating current.

West Burton power stations

The West Burton power stations are a pair of power stations on the River Trent near Gainsborough, Lincolnshire, England. One is a coal-fired power station, which was commissioned in 1967, and the second is a combined cycle gas turbine power station, commissioned in 2013. Both stations are owned and operated by EDF Energy.

Hydrogen-cooled turbo generator

A hydrogen-cooled turbo generator is a turbo generator with gaseous hydrogen as a coolant. Hydrogen-cooled turbo generators are designed to provide a low-drag atmosphere and cooling for single-shaft and combined-cycle applications in combination with steam turbines. Because of the high thermal conductivity and other favorable properties of hydrogen gas this is the most common type in its field today.

A permanent magnet synchronous generator is a generator where the excitation field is provided by a permanent magnet instead of a coil. The term synchronous refers here to the fact that the rotor and magnetic field rotate with the same speed, because the magnetic field is generated through a shaft mounted permanent magnet mechanism and current is induced into the stationary armature.

Hybrid turbocharger

A hybrid turbocharger is an electric turbocharger consisting of a high speed turbine-generator and a high speed electric air compressor. The turbine and compressor are high-speed aeromachines, as in a conventional turbocharger. The electrical motors run at speeds in excess of 120,000 rpm and when used as generators, generate electricity at up to 98.5% electrical efficiency. High electrical efficiency is paramount, because there is no mechanical link between the turbine and compressor. In other words, hybrid turbocharger refers to a series hybrid setup, in which compressor speed and power are independent from turbine speed and power. This design flexibility leads to further improvements in turbine and compressor efficiency, beyond a conventional turbocharger.

Flux switching alternator

A flux switching alternator is a form of high-speed alternator, an AC electrical generator, intended for direct drive by a turbine. They are simple in design with the rotor containing no coils or magnets, making them rugged and capable of high rotation speeds. This makes them suitable for their only widespread use, in guided missiles.

Single-phase generator

Single-phase generator is an alternating current electrical generator that produces a single, continuously alternating voltage. Single-phase generators can be used to generate power in single-phase electric power systems. However, polyphase generators are generally used to deliver power in three-phase distribution system and the current is converted to single-phase near the single-phase loads instead. Therefore, single-phase generators are found in applications that are most often used when the loads being driven are relatively light, and not connected to a three-phase distribution, for instance, portable engine-generators. Larger single-phase generators are also used in special applications such as single-phase traction power for railway electrification systems.

An electric turbo-compound (ETC) system is defined where a turbine coupled to a generator (turbogenerator) is located in the exhaust gas flow of a reciprocating engine to harvest waste heat energy and convert it into electrical power.

References

  1. "The turbogenerator – A continuous engineering challenge" (PDF). Archived from the original (PDF) on 2010-08-21.
  2. http://www.sze.hu/~mgergo/EnergiatudatosEpulettervezes/2013_1_feladat/ErosErika/V%EDzenergia%20hasznos%EDt%E1s%20szigetk%F6zi%20szemmel%20EL%D5AD%C1SANYAG.pdf
  3. Smil, Vaclav (2005). Creating the Twentieth Century . Oxford University Press. pp.  63–64. ISBN   0195168747.
  4. Scientific American . 27 April 1901.Missing or empty |title= (help)
  5. Basic Electrical Engineering (Be 104). McGraw-Hill Education (India) Pvt Limited. 1990. p. 8.1. ISBN   978-1-259-08116-3. Archived from the original on 11 February 2018. Retrieved 8 August 2017.
  6. Basic Electrical Engineering (Be 104). McGraw-Hill Education (India) Pvt Limited. 1990. p. 8.3. ISBN   978-1-259-08116-3. Archived from the original on 11 February 2018. Retrieved 8 August 2017.
  7. Basic Electrical Engineering (Be 104). McGraw-Hill Education (India) Pvt Limited. 1990. p. 8.4. ISBN   978-1-259-08116-3. Archived from the original on 11 February 2018. Retrieved 8 August 2017.
  8. National Electrical Manufacturers Association (11 February 2018). "A chronological history of electrical development from 600 B.C." New York, N.Y., National Electrical Manufacturers Association via Internet Archive.
  9. "Aeroderivative & Heavy-Duty Gas Turbines - GE Power". www.gepower.com. Archived from the original on 2010-05-05.