Here is some knowledge about of Gas Turbine power plant that will help to upgrade the knowledge

1. Gas Turbine Power Plant

2. GAS TURBINES
• Invented in 1930 by Frank Whittle
• Patented in 1934
• First used for aircraft propulsion in 1942 on Me262 by
Germans during second world war
• Currently most of the aircrafts and ships use GT engines
• Used for power generation
• Manufacturers: General Electric, Pratt &Whitney, SNECMA,
Rolls Royce, Honeywell, Siemens – Westinghouse, Alstom
• Indian take: Kaveri Engine by GTRE (DRDO)

3. Selection of Site for Gas Turbine Power Plants
The following factors should be considered while selecting a site for gas turbine power plant:
1. Distance from Load Centre:
The site should be as near to the load centre as possible so that the transmission costs and
losses are minimised.
2. Availability of Land:
The land should be available at cheap rate in order to keep the capital cost of the plant low.
3. Availability of Fuel:
The fuel should be easily available and at reasonable rate.
4. Availability of Transportation Facilities:
The transportation facilities should be available.
5. Distance from Populated Area:
The site should be away from thickly populated area because of noisy operation.
6. Type of Land:
The land should be of high bearing capacity to withstand the load of the plant and also the
vibrations transmitted to the foundations from compressors and turbines.

4. Gas turbine power plant
 Gas turbine:
Working principle :
 Air is compressed(squeezed) to high 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 of the turbine’s power runs the compressor. Part of
it drives the generator/machinery.

5. Gas turbine power plant…
 Gas turbine:
Description:
 Gas turbines burn fuels such as oil,
nature gas and pulverised(powdered)
coal.
 Instead of using the heat to produce
steam, as in steam turbines, gas turbines
use the hot gases directly to turn the
turbine blades.
 Gas turbines have three main parts:
i) Air compressor
ii) Combustion chamber
iii) Turbine

6. Gas turbine power plant…
 Gas turbine:
Air compressor:
 The air compressor and turbine are mounted at either
end on a common horizontal axle(shaft), with the
combustion chamber between them.
 Gas turbines are not self starting. A starting motor
initially drives the compressor till the first combustion
of fuel takes place, later, part of the turbine’s power
runs the compressor.
 The air compressor sucks in air and compresses it,
thereby increasing its pressure.

7. 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 of a solid fuel.
Note :
 The combination of air compressor and
combustion chamber is called as gas
generator.

8. Gas turbine power plant…
 Gas turbine:
Turbine:
o The burning gases expand rapidly and
rush into the turbine, where they cause
the turbine wheels to rotate.
o Hot gases move through a multistage gas
turbine.
o Like in steam turbine, the gas turbine
also has fixed(stationary) and
moving(rotor) blades.
o The stationary blades guide the moving
gases to the rotor blades and adjust its
velocity.
o The shaft of the turbine is coupled to a
generator or machinery to drive it.

9. 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 because of their very high speeds.
 Power generation(used for peak load and as stand-by unit).
Note :
 Gas turbines run at even higher temperatures thansteam turbines,
the temperature may be as high as 1100 – 12600C.

10. Layout of a gas turbine power plant

11. Layout of gas 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.
Intercooler:
 The air after compression in the
LPC is hot. It is cooled by the
intercooler.The intercooler is circulated with
cooling water.

12. Layout of gas turbine power
plant… High pressure compressor(HPC):
 The air from the intercooler enters
the HPC where it is further
compressed to a high pressure.
The compressed air passes
through a regenerator.
 Regenerator(Heat exchanger):
 The air entering the combustion
chamber(CC) for
compressed air entering
combustion chamber.
combustion  Combustionchamber:
must be hot. The heat from the The fuel(natural gas, pulverized coal,
exhaust gases is picked up by the kerosene or gasoline) is injected into the
the combustion chamber.
The fuel gets ignited because of the
compressed air.
The fuel along with the compressed air is
ignited sometimes with a spark plug.

13. Layout of gas turbine power
plant… High pressure compressor(HPC):
 The air from the intercooler enters
the HPC where it is further
compressed to a high pressure.
The compressed air passes
through a regenerator.
 Regenerator(Heat exchanger):
 The air entering the combustion
chamber(CC) for combustion
must be hot. The heat from the
exhaust gases is picked up by the
compressed air entering the
combustion chamber.
 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.
 The fuel along with the compressed
air is ignited sometimes with a spark

14. Layout of gas turbine power
plant…
 High pressure turbine (HPT):
 In the beginning 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 HPT shaft rotates it infact
drives the compressor shaft which
is coupled to it. Now the HPT
runs the compressor and the
starting motor is stopped.
Note :
 About 66%
developed by
of the power
the gas turbine
power plant is used to run the
compressor.
Only 34% of the power developed by
the plant is used to generate electric
power.

15. Layout of gas turbine power
plant…
 Low pressure turbine (LPT):
 The purpose of the LPT is to
produce electric power.
 The shaft of the LPT is directly
coupled with the generator for
producing electricity.
combustion) after leaving
 The hot gases(products of
the
HPT is again sent to a combustion
chamber where it further
undergoes combustion.
 The exhaust gases after leaving
the LPT passes through the
regenerator
exhausted
before being
through the chimney
into the atmosphere.
 The heat from the hot gases is used
to preheat the air entering the
combustion chamber. This preheating
of the air improves the efficiency of the
combustion chamber.

16. 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.
 It is simple in construction. There is no need for boiler, condenser and
other
accessories as in the case of steam power plants.
 Cheaper fuel such as kerosene , paraffin, benzene and powdered coal can
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 – 12600C. 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.

17. Compared to Steam-Turbine, Gas Turbine offers :
1. Greater Power for a given size and weight,
2. High Reliability,
3. Long Life,
4. More Convenient Operation.
5. Engine Start-up Time reduced from 4 hrs to less than 2 min…!!
Gas Turbine Power Plants – Advantages

18. Gas Turbine Power Plants – Applications
Two Major Application Areas:
1. Aircraft Propulsion
2. Electric Power Generation.
Electric Power GenerationAircraft Propulsion

19. Made up of Four Internally Reversible processes:
Brayton Closed Cycle – Analysis
1-2
2-3
3-4
4-1
Isentropic Compression (in a Compressor)
Constant-Pressure Heat Addition
Isentropic Expansion (in a Turbine)
Constant-Pressure Hat Rejection

20. Back Work Ratio
Back WorkRatio
Compressor Work 1
TurbineWork 2
Usually, more than one-half of the
Turbine Work Output is used to drive the
Compressor.
In contrast to Steam Power Plants, where Back Work Ratio is only a few percent.
..!!
This is due to :
1. Liquid is compressed in Steam Power Plants instead of a gas.
2. Steady-Flow Work is proportional to Sp. Volume of the workingfluid.
Therefore, the turbines used in Gas-Turbine Power Plants are larger thanthose
used in Steam Power Plants of the same net power output…!!

21. Regenerative Brayton Cycle
For the Brayton cycle, the turbine exhaust temperature is greater than the
compressor exit temperature. Therefore, a heat exchanger can be placed
between the hot gases leaving the turbine and the cooler gases leaving the
compressor. This heat exchanger is called a regenerator or recuperator..

22. Gas Turbine Cycle – Intercooling
Net Work Output of Gas Turbine can be ↑ by ↓ the Compressor WorkInput.
Multistage + Intercooling…!!!

23. Gas Turbine Cycle – Intercooling
Three Internally Reversible
processes:
1-c Isentropic Compression,
till Pr. is Pi
c-d Constant-Pressure Cooling,
↓ from Tcto Td
d-2 Isentropic Compression,
State 2.

24. Gas Turbine Cycle – Reheat
For Metallurgical Reasons, the Temperature of the Gaseous Combustion Products
entering the turbine must be limited.
This temperature can be controlled by providing Air in Excess of the Amount
required to Burn the Fuel in the combustor.
As a consequence, the gases exiting the combustor contain Sufficient Air to
support the Combustion of Additional Fuel.
Gas Turbine Power Plants take advantage of the Excess Air by means of a
Multistage Turbine with a Reheat Combustor between the stages. With this
arrangement the Net Work per Unit of Mass Flow can be increased.
NOTE : Reheat is used for ↑ in Output Power.
It may not ↑ the Efficiency…!!

25. Gas Turbine Cycle – Reheat
After expansion from State 3 to State a in the first turbine, the gas is Reheated
at Constant Pressure from State a to State b.
The expansion is then completed in the second turbine from State b to State 4.

26. Gas Turbine Cycle – Intercooling + Reheat + Regenerator

27. Brayton with Intercooling,
Reheat, & Regeneration