JET ENGINE

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JET ENGINE

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Contents

• History
• Types of Jet engines
• Major components
• Working
• Advanced Jet planes

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History of Jet Engines
Sir Isaac Newton in the 18th century was the
first to theorize that a rearward-channeled
explosion could propel a machine forward at a
great rate of speed. This theory was based on
his third law of motion. As the hot air blasts
backwards through the nozzle the plane moves
forward.
Henri Giffard built an airship which was
powered by the first aircraft engine, a
three-horse power steam engine. It was very
heavy, too heavy to fly.
In 1874, Felix de Temple, built a monoplane
that flew just a short hop down a hill with the
help of a coal fired steam engine.
Otto Daimler in the late 1800's, invented the
first gasoline engine.
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In 1903, the Wright Brothers flew, "The Flyer",
with a 12 horse power gas powered engine.
From 1903, the year of the Wright Brothers
first flight, to the late 1930s the gas powered
reciprocating internal-combustion engine with a
propeller was the sole means used to propel
aircraft.
It was Frank Whittle, a British pilot, who
designed the first turbo jet engine in 1930.The
first Whittle engine successfully flew in April,
1937. This engine featured a multistage
compressor, and a combustion chamber, a single
stage turbine and a nozzle.
The first jet airplane to successfully use this
type of engine was the German Heinkel He 178
invented by Hans Von Ohain. It was the world's
first turbojet powered flight. 
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The W2/700 engine flew in the Gloster E.28/39,
the first British aircraft to fly with a turbojet
engine, and the Gloster Meteor.
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A jet engine is an engine that discharges a fast
moving jet of fluid to generate thrust in
accordance with Newton's third law of motion.
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Types Of Jet engines

• Water Jets
• Motor Jets
• Turbo jets
• Turbo fans
• Rockets
• Ramjets

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Working principleJet engines are also called as
gas turbines. The engine sucks air in at the
front with a fan. A compressor raises the
pressure of the air. The compressed air is then
sprayed with fuel and an electric spark lights
the mixture. The burning gases expand and blast
out through the nozzle, at the back of the
engine. As the jets of gas shoot backward, the
engine and the aircraft are thrust forward.
TURBO JET ENGINES

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Major components

• Air intake
• Compressors
• Combustors
• Turbines
• Nozzles
• Fuel system
• Cooling system

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Intermediate components

• Turbo pumps
• Afterburners( reheat)
• Thrust reversers

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AIR INTAKE
Fan-The fan is a first component in a turbo fan.
The large spinning fan sucks in large quantity
of air. Most of the fan blades are made up of
titanium. It then speeds this air up and splits
it into two parts. One part continues through
the core or center of the jet engine, where it
is acted upon by other jet engine components.
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The second part bypasses the core of the jet
engine. It goes through a duct which surrounds
the core to the back of jet enginewhere it
produces much of force that propels the airplane
forward. This cooler air helps toquiet the jet
engine as well as adding thrustto the jet engine.
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Compressor - The compressor is the first
component in the jet engine core. The
compressor is made up of fans with many blades
and attached to a shaft. The compressor squeezes
the air that enters it into progressively
smaller areas, resulting in an increase in the
air pressure. This results in an increase in the
energy potential of the air. The squashed air is
forced into the combustion chamber.
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Combustor - In the combustor the air is mixed
with fuel and then ignited. There are as many as
20 nozzles to spray fuel into the air stream.
The mixture of air and fuel catches fire. This
provides a high temperature, high-energy
airflow. The fuel burns with the oxygen in the
compressed air, producing hot expanding gases.
The inside of the combustor is often made of
ceramic materials to provide a heat-resistant
chamber. The heat can reach 2700.
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Turbine - The high-energy airflow coming out of
the combustor goes into the turbine, causing the
turbine blades to rotate. The turbines are
linked by a shaft to turn the blades in the
compressor and to spin the intake fan at the
front. This rotation takes some energy from the
high-energy flow that is used to drive the fan
and the compressor. The gases produced in the
combustion chamber move through the turbine and
spin its blades.
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The turbines of the jet spin around thousands of
times. They are fixed on shafts which have
several sets of ball-bearing in between them.
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Nozzle - The nozzle is the exhaust duct of the
jet engine. This is the jet engine part which
actually produces the thrust for the plane. The
energy depleted airflow that passed the turbine,
in addition to the colder air that bypassed the
engine core, produces a force when exiting the
nozzle that acts to propel the engine, and
therefore the airplane, forward. The combination
of the hot air and cold air are expelled and
produce an exhaust, which causes a forward
thrust.
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The nozzle may be preceded by a mixer, which
combines the high temperature air coming from
the jet engine core with the lower temperature
air that was bypassed in the fan. The mixer
helps to make the jet engine quieter.
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Variable Exhaust Nozzle, on the GE F404-400
low-bypass turbofan installed on a Boeing F-18
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Turbopumps
Turbo pumps are centrifugal pumps which are spun
by gas turbines and are used to raise the
propellant pressure above the pressure in the
combustion chamber so that it can be injected
and burnt. Turbo pumps are very commonly used
with rockets, but ramjets and turbojets also
have been known to use them.
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Afterburners (reheat)
Due to temperature limitations with the gas
turbines, jet engines do not consume all the
oxygen in the air ('run stochiometric').
Afterburners burn the remaining oxygen after
exiting the turbines, but usually do so
inefficiently due to the low pressures existing
at this part of the jet engine however this
gains thrust, which can be useful.
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Thrust reversers
Thrust reversal, also called reverse thrust, is
the temporary diversion of an aircraft engine's
exhaust or changing of propeller pitch so that
the thrust produced is directed forward, rather
than aft. This acts against the forward travel of
the aircraft, providing deceleration.
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Feul system
Apart from providing fuel to the engine, the fuel
system is also used to control propeller speeds,
compressor airflow and cool lubrication oil. Fuel
is usually introduced by an atomized spray, the
amount of which is controlled automatically
depending on the rate of airflow.
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. It also increases the energy extracted by the
turbine which drives the compressor even faster
and so there is an increase in air flowing into
the engine as well.
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Cooling system
Cooling air then passes through complex passages
within the turbine blades. After removing heat
from the blade material, the air (now fairly hot)
is vented, via cooling holes, into the main gas
stream. Cover plates are incoperated on blades
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This acts as a centrifugal compressor to
pressurize the cooling air before it enters the
blade. Another solution is to use an
ultra-efficient turbine rim seal to pressurize
the area where the cooling air passes across to
the rotating disc.
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