Blog on gas turbine power plant (Part 2- working of
plant and parts )
VIDEO 1
VIDEO 2
SEE BOTH THE VIDEOS FOR BETTER EXPLANATION
Gas turbine functions in the same way
as the Internal Combustion engine. It sucks in air from the atmosphere,
compresses it. The fuel is injected and ignited. The gases expand doing work
and finally exhausts outside. The only difference is instead of the reciprocating
motion, gas turbine uses a rotary motion throughout.
This article
will explain the three main sections of the Gas Turbine.
1.
Compressor.
The compressor sucks in air form
the atmosphere and compresses it to pressures in the range of 15 to 20 bar. The
compressor consists of a number of rows of blades mounted on a shaft. This is
something like a series of fans placed one after the other. The pressurized air
from the first row is further pressurised in the second row and so on.
Stationary vanes between each of the blade rows guide the air flow from one
section to the next section. The shaft is connected and rotates along with the
main gas turbine.
2.
Combustor.
This is an annular chamber where
the fuel burns and is similar to the furnace in a boiler. The air from the
compressor is the Combustion air. Burners arranged circumferentially on the
annular chamber control the fuel entry to the chamber. The hot gases in the
range of 1400 to 1500 °C leave the chamber with high energy levels. The chamber
and the subsequent sections are made of special alloys and designs that can
withstand this high temperature.
3.
Turbine
The turbine does the main work of
energy conversion. The turbine portion also consists of rows of blades fixed to
the shaft. Stationary guide vanes direct the gases to the next set of blades.
The kinetic energy of the hot gases impacting on the blades rotates the blades
and the shaft. The blades and vanes are made of special alloys and designs that
can withstand the very high temperature gas. The exhaust gases then exit to
exhaust system through the diffuser. The gas temperature leaving the Turbine is
in the range of 500 to 550 °C.
The gas
turbine shaft connects to the generator to produce electric power. This is
similar to generators used in conventional thermal power plants.
Performance
More than Fifty percent of the energy
converted is used by the compressor. Only around 35 % of the energy input is
available for electric power generation in the generator. The rest of the
energy is lost as heat of the exhaust gases to the atmosphere.
Three parameters that affect the
performance of a of gas turbine are
1.
The pressure of
the air leaving the compressor.
2.
The hot gas
temperature leaving the Combustion chamber.
3.
The gas
temperature of the exhaust gases leaving the turbine.
The above is a simple description of the
Gas Turbine. Actually it is a very sophisticated and complex equipment which
over the years have become one of the most reliable mechanical equipment.
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