Gas Turbine Power Plant

Gas Turbine Power Plant

By

Mr.B.Ramesh, M.E.,(Ph.D) Research Scholar, CEG, Anna Universit University, y, Chennai. Associate Professor of Mechanical Engineering, St. Joseph¶s College of Engineering, Eng ineering, Jeppiaar Trust, Chennai-119

Unit

IIII II ± Pow Power er plant plant engine engineeri ering ng Gas turbine power plant

 Gas turbine: Working principle :

Airr is co comp mpre ress ssed ed(s (squ quee eeze zed) d) to hi high gh  Ai  pressure by a fan-like device called the compressor.  Then fuel and compressed air are mixed

in a combustion chamber and ignited.  Hot gases are given off, which spin the

turbine wheels. Most st of th thee tur urbi bine ne¶¶s po powe werr ru runs ns th thee  Mo compressor. Part of generator/machinery.

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it

drives

the

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Unit

IIII II ± Pow Power er plant plant engine engineeri ering ng Gas turbine power plant«

 Gas turbine: Description:

 Gas Gas tu turb rbin ines es bu burrn fu fuel elss su such ch as oi oil, l, natu na ture re ga gass an and d pu pulv lver eris ised ed(p (pow owde dere red) d) coal.

nste tead ad of us usin ing g th thee he heat at to pr prod oduc ucee  Ins steam, as in steam turbines, gas turbines usee th us thee ho hott ga gase sess di dire rect ctly ly to turn turn th thee turbine blades. 

Gas turbines have three main parts:

i)

Air co com mpr pres esssor 

ii)) ii

Combus Com busti tion on cha chamb mber  er 

iii) ii i) Tu Turb rbin inee 4 November 2010

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Unit

IIII II ± Pow Power er plant plant engine engineeri ering ng Gas turbine power plant«

 Gas turbine: Air compressor: 

The ai airr com ompr preesso sorr and tur urbi bine ne are mou ount nted ed at ei eith ther er en end d on a co com mmon horizontal axle(shaft), with the combustion chamber between them.



Gas tu Gas turb rbin ines es ar aree no nott se self lf st star arti ting ng.. A starting motor initially dr driives the compressor till the first combustion of  fuel takes place, later, part of the turbine¶s power runs the compressor.



The ai The airr com ompr pres esso sorr su succks in ai airr an and d comp co mpre ress sses es it it,, th ther ereb eby y in incr crea easi sing ng it itss  pressure.

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Unit

IIII II ± Pow Power er plant plant engine engineeri ering ng Gas turbine power plant«

 Gas turbine: Combustion chamber:  In

the combustion chamber, the compressed air combines with fuel and the resulting mixture is burnt.

 The greater the pressure of air, the better 

the fuel air mixture burns.  Modern gas turbines usually use liquid

fuel, but they may also use gaseous fuel, natural gas or gas produced artificially  by gasification gasification of a solid fuel.  Note :  The combination of air compressor and

combus comb usti tion on ch cham ambe berr is ca call lled ed as ga gass generator. 4 November 2010

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Unit

IIII II ± Pow Power er plant plant engine engineeri ering ng Gas turbine power plant«

 Gas turbine: Turbine: o

o

o

o

o

The burning gases expand rapidly and rush into the turbine, where they cause the turbine wheels to rotate. Hot gases move through a multistage gas turbine. Like in st Like stea eam m tu turb rbin ine, e, th thee ga gass turb turbin inee also has fixed(stationary) and moving(rotor) moving(r otor) blades. The stationary blades guide the moving gases to the rotor blades and adjust its velocity. The shaft of the turbine is coupled to a generator or machinery to drive it.

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Unit

IIII II ± Pow Power er plant plant engine engineeri ering ng Gas turbine power plant«

 Applications of gas turbine:  Gas turbines are used to drive pumps, compressors and high speed cars.  Used in aircraft and ships for their propulsion. They are not suitable for 

automobiles automobil es because of their very high h igh speeds. 

Power generation(used for peak load and as stand-by unit).

 Note : 

Gas tu Gas turb rbin ines es ru run n at ev even en hi high gher er te tem mpe pera ratu ture ress th than an st stea eam m tu turb rbin ines es,, th thee temperature temper ature may be as high as 1100 110 0 ± 12600C.



The thermal efficiency of gas turbine made of metal components do not exceed 36%.



Res eseear arcch is un unde derw rwaay to us usee cer eram amiic co com mpo pone nent ntss at tur urbi bine ne inl nlet et temperature temper ature of 13500C or more, and reach thermal efficiencies over 40% in a 300 k W unit.

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Layout

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of a gas turbine power plant

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Layout 

of gas ga s turbine power plant«

Starting motor:

 Gas turbines are not self starting.

They require a starting motor to first bring the turbine to the minimum speed called coming ±in speed, for this purpose a starting motor is required. 

Low pressure compressor(LPC):

 The purpose of the compressor is

to compress the air. Air from the atmosphere is drawn into the LPC and is compressed.

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Intercooler: The air after compression in the LPC

is hot. It is cooled by the intercooler. Thee int Th nter erco cool oler er is ci circ rcul ulaate ted d wi with th cooling water water.. 9

Layout 

of gas ga s turbine power plant«

High pressure compressor(HPC):

 The air from the intercooler enters

the HPC where it is further  comp co mpre ress ssed ed to a hi high gh pr pres essu sure re.. The compressed air passes through a regenerator. 

Regenera Rege nerator(H tor(Heat eat excha exchanger) nger)::

airr en ente terin ring g the com combus busti tion on  The ai cha ham mbe ber( r(C CC) for com omb bus usttion must be hot. The heat from the exhaust gases is picked up by the compressed air entering the combustion chamber.

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 Combustion chamber:

fuel(n l(nat atur ural al ga gas, s, pul pulve veriz rized ed co coal al,, The fue kerosene or gasoline) is injected into the combustion chamber ch amber.. Thee fu fuel el ge gets ts igni gnite ted d be beca caus usee of th thee Th compressed air air..  The fuel along with the compressed air  is ignited sometimes with a spark plug. 10

Layout 

of gas ga s turbine power plant«

High pressure compressor(HPC):

 The air from the intercooler enters

the HPC where it is further  comp co mpre ress ssed ed to a hi high gh pr pres essu sure re.. The compressed air passes through a regenerator. 

Regenera Rege nerator(H tor(Heat eat excha exchanger) nger)::

airr en ente terin ring g the com combus busti tion on  The ai cha ham mbe ber( r(C CC) for com omb bus usttion must be hot. The heat from the exhaust gases is picked up by the compressed air entering the combustion chamber.

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 Combustion chamber: The fuel(natural gas, pulverized coal,

kerosene or gasoline) is injected into the combustion chamber. The fuel gets ignited because of the compressed air air..  The fuel along with the compressed air is ignited sometimes with a spark  11  plug.

Layout 

of gas ga s turbine power plant«

High pressure turbine (HPT):

 In

the be beg ginning the starting motor runs the compressor shaft.

 The

hot gases(products of  combustion) expands through the high pressure turbine.

 It is important to note that when

the HP HPT T sha haft ft ro rota tate tess it in infa fact ct drives the compressor shaft which is coupled to it. Now the HPT runs the compressor and the starting motor is stopped.  Note :

Only 34% of the power developed by

the pl the plan antt is us used ed to ge gene nera rate te el elec ectr tric ic 66% of the power    power.  About developed by the gas tu turrbine   pow poweer pl plaant is use used to run the compressor.

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Layout 

of gas ga s turbine power plant«

Low pressure turbine (LPT):

purrpose of the LPT is to  The pu  produce electric power.  The shaft of the LPT is directly

couple coup led d wi with th th thee ge gene nera rato torr fo for  r   producing electricity.  The

hot gases(products of  com co mbu bust stio ion) n) af afte terr le leav aviing th thee HPT is again sent to a combustion chamber where it further  undergoes combustion.

exhau aust st gas gases es aft after er le leav aving ing  The exh the LPT passes through the regenerator before being exha ex haus uste ted d th thro roug ugh h th thee ch chim imney ney into the atmosphere. 4 November 2010

 The heat from the hot gases is used

to preheat the air entering the combusti com bustion on cham chamber ber.. Thi Thiss prehe preheati ating ng of the air improves the efficiency of the combustion chamber. 13

Gas turbine power plant«  Advantages of gas turbine power plant :  Storage of fuel requires less area and handling is easy.  The cost of maintenance is less. construction. on. There is no need for boiler, condenser and other   It is simple in constructi accessories as in the case of steam power plants. paraffin, n, benzene and powdered p owdered coal can  Cheaper fuel such as kerosene , paraffi  be used which are cheaper than petrol and diesel.  Gas turbine plants can be used in water scarcity areas.  Less pollution and less water is required.  Disadvantages

of gas turbine power plant :

 66% of the power developed is used to drive the compressor. Therefore

the gas turbine unit has a low thermal efficiency.  The running speed of gas turbine is in the range of (40,000 to 100,000 rpm) and the operating temperature is as high as 1100 ± 1260 0C. For this reason special metals and alloys have to be used for the various parts of  the turbine.  High frequency noise from the compressor is objectionable. 4 November 2010

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Videos

and Animations

1.

How a gas turbine engine works

2.

Gas turbine working principle

3. 3 Gas turbine power plant.swf 

Thank You

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