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Cycles usedin Jet Engines
CLASS 5
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Jet enginesJet engines move the airplane
forward with a great force that isproduced by a tremendousthrust and causes the plane tofly very fast.
All jet engines, which are alsocalled gas turbines, work on thesame principle.
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Jet engines
The image below shows how theair flows through the engine.
The air goes through the core ofthe engine as well as around thecore.
This causes some of the air to be
very hot and some to be cooler. The cooler air then mixes with the
hot air at the engine exit area.
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What is Thrust?
Thrustis the forward force thatpushes the engine and, theairplane forward.
An engine uses principle:
"every action there is anequal and opposite reaction."
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Jet TrustThe engine takes in a large
volume of air.The air is heated and
compressed and sloweddown.
The air is forced throughmany spinning blades.
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Jet Trust By mixing this air with jet
fuel, the temperature of theair can be as high as threethousanddegrees.
The power of the air is used toturn the turbine.
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Jet TrustFinally, when the air
leaves, it pushesbackward out of theengine.
This causes the plane tomove forward.
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Jet Engine Design1
2 3 4 56
diffuser
compressor
combustion chamber turbine nozzle
1
2
3
4
5
6
P=constant
P=constant
qout
qin
T
s
1-2 Isentropic compression in diffuser
2-3 Isentropic compression through compressor
3-4 Constant pressure heat additionin combustion chamber
4-5 Isentropic expansion through turbine
5-6 Isentropic expansion in nozzle
6-1 Constant pressure heat rejection
Idealized air-standard
Brayton cycle
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Isentropic
compressionCompression which
occurs without anychange in entropy.
Entropy =
"disorder"(Greek)
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Parts of a Jet Engine
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FanFan - The fan is the first component in aturbofan. The large spinning fan sucks in
large quantities of air. Most blades of thefan are made of titanium. It then speedsthis air up and splits it into two parts. Onepart continues through the "core" or
center of the engine, where it is actedupon by the other engine components.
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FanThe second part "bypasses" the core ofthe engine. It goes through a duct that
surrounds the core to the back of theengine where it produces much of theforce that propels the airplane forward.This cooler air helps to quiet the engine as
well as adding thrust to the engine.
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CompressorCompressor - The compressor
is the first component in theengine core.The compressor is made up
of fans with many blades and
attached to a shaft.
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Compressor The compressor squeezes the air
that enters it into progressively
smaller areas, resulting in anincrease in the air pressure.
This results in an increase in theenergy potential of the air.
The squashed air is forced intothe combustion chamber.
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Combustor
Combustor - In the combustorthe air is mixed with fuel and
then ignited.There are as many as 20 nozzles
to spray fuel into the airstream.
The mixture of air and fuelcatches fire
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Combustor
This provides a high
temperature, high-energyairflow.
The fuel burns with theoxygen in the compressed
air, producing hotexpanding gases.
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Combustor
The inside of the
combustor is often made ofceramic materials toprovide a heat-resistant
chamber.The heat can reach 2700.
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Turbine
Turbine - The high-energy airflowcoming out of the combustor
goes into the turbine, causingthe turbine blades to rotate.
The turbines are linked by ashaft to turn the blades in the
compressor and to spin theintake fan at the front.
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Turbine
This rotation takes some energyfrom the high-energy flow that is
used to drive the fan and thecompressor.
The gases produced in thecombustion chamber move
through the turbine and spin itsblades.
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Turbine
The turbines of the jet spin
around thousands of times.They are fixed on shafts
which have several sets of
ball-bearing in betweenthem.
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Nozzle
Nozzle - The nozzle is the
exhaust duct of theengine.This is the engine part
which actually producesthe thrust for the plane.
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Nozzle
The energy depleted airflow thatpassed the turbine, in addition to
the colder air that bypassed theengine core, produces a forcewhen exiting the nozzle that actsto propel the engine, and
therefore the airplane,forward.
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Nozzle
The combination of the
hot air and cold air areexpelled and producean exhaust, whichcauses a forward thrust.
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mixerThe nozzle may be preceded by
a mixer, which combines the
high temperature air comingfrom the engine core with thelower temperature air that wasbypassed in the fan.
The mixer helps to make theengine quieter.