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Gas turbines have been used for electricity generation. Gas turbines are ideal for this application as they
can be started and stopped quickly . There are twobasic types of gas turbines
Aero derivative and,
Industrial.Over the last ten years there have been majorimprovements to the sizes and efficiencies of these gasturbines.
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Layout gas turbine power plant
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How does a Gas Turbine Work?Gas turbines use the hot gas produced by burning a fuel to drive a
turbine. They are also called combustion turbines or combustion gasturbines.
Because some of its heat and pressure energy has been
transferred to the turbine, the gas is cooler and at a lowerpressure when it leaves the turbine. It is then eitherdischarged up a chimney (often called a stack) or isdirected to a special type of boiler, called a Heat Recovery
Steam Generator (HRSG), where most of the remainingheat energy in the gas is used to produce steam .
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MODEL DESIGN
The cross section of a typical large gas turbine
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Gas Turbine System
A schematic of a gas turbine-based CHP system. Somecombined cycles extract steam at an intermediate pressurefor use in industrial processes and are combined cycle CHPsystems
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The photo shows, for a large gas turbine ,
The photo shows, for a large gas turbine, the cross-section of a typical burner/combustor combination, thearrangement of these combustors and the area betweenthe combustors and the turbine. The heat resistantceramic tiles used in these hot areas can be clearly seen.
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Air Compressor
The air compressors used in gas turbines are made up of several rows of blades (similar to the blades on ahousehold fan). Each row of blades compress and push theair onto the next row of blades. As the air becomes moreand more compressed, the sizes of the blades becomesmaller from row to row. The row of largest blades can beseen at the left end of the compressor in the photo above, with the smallest blades to the right (the direction of airflow is from left to right). Note: A row of blades fixed tothe outer casing of the compressor is also located aftereach row of moving blades
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Inlet Air
The air coming into the compressor of a gasturbine must be cleaned of impurities (such as
dust and smoke) which could erode or stick to theblades of the compressor or turbine, reducing thepower and efficiency of the gas turbine. Dry filtersor water baths are usually used to carry out thiscleaning.
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Burners and Combustors
The compressed air and fuel is mixed and metered inspecial equipment called burners. The burners areattached to chambers called combustors. The fuel & airmixture is ignited close to the exit tip of the burners, then
allowed to fully burn in the combustors. The temperatureof the gas in the combustors and entering the turbine canreach up to 1350C. Special heat resistant materials (suchas ceramics) are used to line the inside walls of thecombustors. The area between the combustors and theturbine are also lined.
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Noise
The inlet air (blue) enters the compressor at the left. Theexhaust gas (red) leaves the turbine at the right. Theburners and combustors are located between thecompressor and turbineGas turbines are very compact and occupy small groundarea.. Silencers are usually fitted in the inlet air and exhaustgas ducts.
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Gas Turbines
Gas turbines are an established technology available in sizes ranging from severalhundred kilowatts to over several hundred megawatts. Gas turbines produce highquality heat that can be used for industrial or district heating steam requirements.
Alternatively, this high temperature heat can be recuperated to improve theefficiency of power generation or used to generate steam and drive a steam turbinein a combined-cycle plant. Gas turbine emissions can be controlled to very lowlevels using dry combustion techniques, water or steam injection, or exhausttreatment. Maintenance costs per unit of power output are about a third to a half of reciprocating engine generators. Low maintenance and high quality waste heatoften make gas turbines a
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Half compressor
The combustion (gas) turbines being installed in many of today'snatural-gas-fueled power plants are complex machines, but they basically involve three main sections:The compressor which draws air into the engine, pressurizes it, andfeeds it to the combustion chamber literally at speeds of hundreds of miles per hour.
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