This document provides an overview of a seminar report on turbofan engines. It includes an introduction, acknowledgements, table of contents, and sections on the propulsion system, aircraft motion, aircraft engines, and the key components of a turbofan engine including the air intake, compressors, combustion chamber, turbines, and outlet. The sections describe the purpose and functioning of each component, with the overall aim of explaining how a turbofan engine converts energy to provide propulsion to aircraft.

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SEMINAR REPORT
On
TURBOFAN ENGINE
Submitted in partial fulfilment of the requirements
Of the degree of
Bachelor of Technology
In
Mechanical Engineering
MAHARAJA AGARSAIN INSTITUTE OF TECHNOLOGY (under AKTU)
PILUKHWA, HAPUR, UTTAR PRADESH
Submitted to :- Submitted by:-
Mr. DEEPAK BHASKAR (Assistant Professor) SHAILESH KUMAR
HOD-MECHANICAL DEPARTMENT Roll no: 1333240066
MAIT, GHAZIABAD B.tech-4th
YEAR

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ACKNOWLEDGEMENT
I express my sincere thanks to my guide Mr. Deepak Bhaskar, Head Of Department,
Mechanical Department, MAHARAJA AGARSAIN INSTITUTE OF TECHNOLOGY,
Ghaziabad, for guiding me right from the inception till the successful completion. I sincerely
acknowledge him for extending his valuable guidance, support for literature, critical reviews of
seminar report and above all the moral support he had provided to me with all stages of the
seminar.
Finally, I would like to add few heartfelt words for the people who were the part of the seminar
in various ways, especially my friends and classmates who gave me unending support right from
the beginning. My family has been the most significant in my life so far and this part of my life
has no exception. Without their support, persistence and love I would not be where I am today.
SHAILESH KUMAR
Mechanical Engineering
4TH Year, 8th Sem.
1333240066
MAHARAJA AGARSAIN INSTITUTE OF TECHNOLOGY

3. 2
CONTENT
Serial No. Title page no:
1. Introduction 1
2. Propulsion System 2
3. Aircraft motion 3-4
4. Aircraft Engine 4-5
5. Turbofan engine 6-7
5.1 Air Intake /fan 7-8
5.2 Compressors 8-9
5.3 Combustion Chamber 9
5.4 Turbines 10
5.5 Outlet/nozzle 11
6. Jet Propulsion 11
6.1 Turbojet 12
6.2 Ramjet 13
6.3 Rocket 14-15
7. Conclusion 16
8. References 17

4. 3
1. Introduction
An aircraft is a machine that is able to fly by gaining support from the air. It counters the force of
gravity by using either static lift or by using the dynamic lift of an air foil, or in a few cases the
downward thrust from jet engines.
The human activity that surrounds aircraft is called aviation. Crewed aircraft are flown by an on-
board pilot, but unmanned aerial vehicles may be remotely controlled or self-controlled by on-
board computers. Aircraft may be classified by different criteria, such as lift type, aircraft
propulsion, usage and others.
Propulsion is a means of creating force leading to movement. The term is derived from two Latin
words: pro, meaning before or forward; and pellere, meaning to drive. A propulsion system
consists of a source of mechanical power, and a propulsor (means of converting this power into
propulsive force).
A technological system uses an engine or motor as the power source, and wheels and axles,
propellers, or a propulsive nozzle to generate the force. Components such as clutches or
gearboxes may be needed to connect the motor to axles, wheels, or propellers.
Biological propulsion systems use an animal's muscles as the power source, and limbs such as
wings, fins or legs as the propulsors.
Some aircraft, like airliners and cargo planes, spend most of their life in a cruise condition. For
these airplanes, excess thrust is not as important as high engine efficiency and low fuel usage.
Since thrust depends on both the amount of gas moved and the velocity, we can generate high
thrust by accelerating a large mass of gas by a small amount, or by accelerating a small mass of
gas by a large amount. Because of the aerodynamic efficiency of propellers and fans, it is more
fuel efficient to accelerate a large mass by a small amount. That is why we find high bypass fans
and turboprops on cargo planes and airliners.
Some aircraft, like fighter planes or experimental high speed aircraft require very high excess
thrust to accelerate quickly and to overcome the high drag associated with high speeds. For these
airplanes, engine efficiency is not as important as very high thrust. Modern military aircraft
typically employ afterburners on a low bypass turbofan core. Future hypersonic aircraft will
employ some type of ramjet or rocket propulsion.

5. 4
2. Propulsion System
Propulsion is a means of creating force leading to movement. The term is derived from two Latin
words: pro, meaning before or forward; and puller, meaning to drive. A propulsion system
consists of a source of mechanical power, and a propulsor (means of converting this power into
propulsive force).
An aircraft propulsion system generally consists of an aircraft engine and some means to
generate thrust, such as a propeller or a propulsive nozzle.
An aircraft propulsion system must achieve two things. First, the thrust from the propulsion
system must balance the drag of the airplane when the airplane is cruising. And second, the
thrust from the propulsion system must exceed the drag of the airplane for the airplane to
accelerate. In fact, the greater the difference between the thrust and the drag, called the excess
thrust, the faster the airplane will accelerate.
Some aircraft, like airliners and cargo planes, spend most of their life in a cruise condition. For
these airplanes, excess thrust is not as important as high engine efficiency and low fuel usage.
Since thrust depends on both the amount of gas moved and the velocity, we can generate high
thrust by accelerating a large mass of gas by a small amount, or by accelerating a small mass of
gas by a large amount. Because of the aerodynamic efficiency of propellers and fans, it is more
fuel efficient to accelerate a large mass by a small amount. That is why we find high bypass fans
and turboprops on cargo planes and airliners.
Some aircraft, like fighter planes or experimental high speed aircraft, require very high excess
thrust to accelerate quickly and to overcome the high drag associated with high speeds. For these
airplanes, engine efficiency is not as important as very high thrust. Modern military aircraft
typically employ afterburners on a low bypass turbofan core. Future hypersonic aircraft will
employ some type of ramjet or rocket propulsion.
A propeller or airscrew comprises a set of small, wing-like aerofoil blades set around a central
hub which spins on an axis aligned in the direction of travel. The blades are set at a pitch angle to
the airflow, which may be fixed or variable, such that spinning the propeller creates aerodynamic
lift, or thrust, in a forward direction.

6. 5
3. Aircraft Motion
This slide shows some rules for the simplified motion of an aircraft. By simplified motion we
mean that some of the four forces acting on the aircraft are balanced by other forces and that we
are looking at only one force and one direction at a time. In reality, this simplified motion doesn't
occur because all of the forces are interrelated to the aircraft's speed, altitude, orientation, etc.
But looking at the forces ideally and individually does give us some insight and is much easier to
understand.
In an ideal situation, an airplane could sustain a constant speed and level flight in which the
weight would be balanced by the lift, and the drag would be balanced by the thrust. The closest
example of this condition is a cruising airliner. While the weight decreases due to fuel burned,
the change is very small relative to the total aircraft weight. In this situation, the aircraft will
maintain a constant cruise velocity as described by Newton's first law of motion.
If the forces become unbalanced, the aircraft will move in the direction of the greater force. We
can compute the acceleration which the aircraft will experience from Newton's second law of
motion
F = m * a
Where a is the acceleration, m is the mass of the aircraft, and F is the net force acting on the
aircraft. The net force is the difference between the opposing forces; lift minus weight, or thrust
minus drag. With this information, we can solve for the resulting motion of the aircraft.
If the weight is decreased while the lift is held constant, the airplane will rise:
Lift > Weight - Aircraft Rises
If the lift is decreased while the weight is constant, the plane will fall:
Weight > Lift - Aircraft Falls
Similarly, increasing the thrust while the drag is constant will cause the plane to accelerate:
Thrust > Drag - Aircraft Accelerates
And increasing the drag at a constant thrust will cause the plane to slow down:
Drag > Thrust - Aircraft Slows

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Fig-a-forces acting on aircraft
4. Aircraft Engine
The Merriam-Webster dictionary defines an engine as a machine for converting any of various
forms of energy into mechanical force and motion. The engine is thus an energy transformer.
Energy (also called work, and quantified in Joules) can itself be interpreted as a force in motion.
In the well-known case of a car engine, the thermal energy coming from the 20 combustion of
petrol and air is transformed into mechanical energy which is applied to the wheels of the vehicle
(the force allowing to turn the wheels).The more familiar notion of power, quantified in Watts
(or in horse-power by our parents and grandparents – 1 horse power = 736 Watts) expresses the
quantity of energy used in one unit of time.
This transformation is unfortunately not perfect and is necessarily accompanied by certain losses.
This introduces the notion of efficiency. The efficiency is defined as the ratio between the result
obtained (the mechanical energy transmitted to the wheels in the example of a car engine) and
the means used to produce it (thermal energy contained in the petrol-air mixture in this example).
Its value is always less than 1 (or 100%). As an example, a petrol engine and a diesel engine give
respectively efficiencies of the order of 35% and 46%. In a traffic jam, this efficiency can reduce
to 15%. The lost energy is generally transformed into heat.

8. 7
Fig-b-Aircraft Engine
In flight, an aircraft does not have wheels in contact with the ground. We therefore need to
define the way of generating energy to allow it to advance. The principle of aeronautical
propulsion is a direct application of Newton’s third law of motion (principle of opposite action or
action-reaction) which says that any body A exerting a force on a body B experiences a force of
equal intensity, exerted on it by body B. In the case of aeronautical propulsion, the body A is
atmospheric air which is accelerated through the engine. The force – the action – necessary to
accelerate this air has an equal effect, but in the opposite direction – the reaction -, applied to the
object producing this acceleration (the body B, that is the engine, and hence the aircraft to which
it is attached).
It is possible to imagine much simpler examples based on the same principle. The first, probably
the most simple, is that of the fairground balloon, which is first inflated then released. The air
(body A) is ejected from the balloon (body B) through a small opening and at high speed. The
balloon is propelled in the opposite direction to the ejected air – this is the reaction. The second
example is that of a rotating watering system.
The speed of water (body A) is increased by its passage through small ejection holes. The two
arms of the watering system (body B) are pushed in the opposite direction (reaction), thus
driving the rotation.

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5.Turbofan engine
A Turbofan engine is also called a combustion turbine, is a type of internal combustion engine. It
has an upstream rotating compressor coupled to a downstream turbine, and a combustion
chamber in between.
The basic operation of the gas turbine is similar to that of the steam power plant except that air is
used instead of water. Fresh atmospheric air flows through a compressor that brings it to higher
pressure. Energy is then added by spraying fuel into the air and igniting it so the combustion
generates a high-temperature flow. This high-temperature high-pressure gas enters a turbine,
where it expands down to the exhaust pressure, producing a shaft work output in the process. The
turbine shaft work is used to drive the compressor and other devices such as an electric generator
that may be coupled to the shaft. The energy that is not used for shaft work comes out in the
exhaust gases, so these have either a high temperature or a high velocity. The purpose of the gas
turbine determines the design so that the most desirable energy form is maximized. Gas turbines
are used to power aircraft, trains ships, electrical generators, or even tanks.
The example proposed here is the simplest that can be imagined for an engine. This is composed
of 5 main parts:
 The air intake /fan
 The compressor
 The combustion chamber
 The turbine
 The outlet (jet pipe and propelling nozzle)

10. 9
The purpose of the following parts are-
1. Suck atmospheric air into the engine (air describe briefly these components. Their inte-
intake and compressor) gration serves to:
2. Increase the energy of this air by means of the compressor (increasing the pressure) and
the combustion chamber (increasing the temperature by burning a mixture of air and kerosene)
3. Transforming this energy into speed (kinetic energy) by means of the outlet tube in order
to apply the principle of aeronautical propulsion described above.
Fig-c-working of gas turbine

11. 10
5.1 The Air Intake
The air intake is one of the most visible parts of an aircraft engine. A typical photo of this
component is shown on the right picture. This envelope which precedes the main part of the
engine is attached to a strut, which is itself fixed to a wing or the fuselage. The main purposes of
this nacelle are:
 to present as little air resistance (drag) as possible
 to guarantee optimal functioning of the engine during the different phases of flight (take-
off, cruise, landing)
 to limit the acoustical disturbance of the engine by absorbing some of the noise
 to protect the inlet parts of the engine from phenomena relating to icing (the local
temperature at 10 000 metres altitude is between -40° and -50°C)

12. 11
5.2 The Compressor
The compressor, situated just behind the air intake, is the first element which allows
transformation of energy, in this case from mechanical energy into energy in the form of
pressure. This machine is presented at the bottom left, where the flow is from left to right.
The compressor is composed of a series of fixed blades, both fixed (stators – coloured in grey in
the figure) and moving (rotors – coloured in blue, yellow and red in the figure). The function of
these blades is to transform the mechanical energy which turns the rotors into pressure energy.
This transformation operates by directing in a precise way the flow which develops in the
channels defined by the blades and the envelope of the engine. The rotor which is best known is
the one coloured in blue in Figure at the left; this is also called the fan and can be seen at the
entrance of the engine. Air from the atmosphere is sucked into the engine by the compressor in
the same way that a ventilator fan (which is nothing else but a type of compressor) sucks air into
a polluted room.
The compressor of a modern engine allows pressures typically 30 or 40 times greater to be
reached at the outlet of this element. The fan turns at a rotational speed of the order of 5000
revolutions per minute: the largest diameters are of the order of 3.25 metres, the length of the
blades of the largest fans is greater than 1.20 meters. The centrifugal force undergone by
transport aircraft these rotating blades is comparable to the weight of a railway carriage (80
000kg) being attached to the end of one of these blades.
Fig-d-compressor

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5.3 The Combustion Chamber
The combustion chamber, situated just downstream from the compressor, is the element in which
thermal energy is added to the pressure energy accumulated at the outlet of the compressor. The
transformation of energy considered here comes from the combustion of the air/kerosene mixture
(the combustible used in most aircraft engines) which generates an increase in the temperature of
the air passing through the engine.
Calculations show that the efficiency of the engine will be better if the temperature at the outlet
of the combustion chamber is higher. In the most recent engines, temperatures of the order of
2100°C are achieved. To understand this temperature, it is useful to remember that the
temperature of the flame of a wood fire is only about 1000°C. The materials used for the
construction of a combustion chamber contain an important fraction of nickel and chrome. The
melting temperature of these two metals is less than this 2100°C and protection and cooling of
the metal parts is therefore absolutely necessary. A description of such technologies is outside
the scope of this document.
In summary then, at the outlet of the combustion chamber, there is a mixture of burnt air and
kerosene at very high temperature and pressure.
fuel

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5.4 Turbine
The turbine is situated at the outlet of the combustion chamber. Its function is to transform the
energy available in the form of pressure and temperature into mechanical energy. In other words,
the turbine is the “motor” which turns the com- pressure. The pressure and temperature of the air
kerosene mixture will decrease during passage through this element. This part of the machine is
presented in Left Figure.
As for the compressor, the turbine is composed of a series of blades, both fixed (stators –
coloured in grey in the figure) and moving (rotors – coloured in red, yellow and blue in the
figure). The function of these rotors is to transform the temperature and pressure energy into
mechanical energy which turns the compressor. This transformation is also made by precisely
directing the flow which develops in the channels defined by the blades and the envelope of the
engine. As an example, the red rotor in Left Figure is generally composed of 30 to 40 blades.
Each one of these generates the same energy as is generated by the entire engine of a Formula
One car!
Calculations show that the complete transformation of the energy available in the form of
pressure and temperature and the energy available in the kerosene gives more mechanical energy
than is needed to turn the compressor (typically twice as much). The turbine serves then to
transform only the quantity of energy strictly required to achieve this function. The 50%
available energy which remains in the air/kerosene mixture is transformed into kinetic energy
(the speed necessary to guarantee propulsion of the aircraft).
Fig-e-turbine

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5.4 The Outlet
This last element, situated at the back of the turbine, is the outlet tube. In this tube the last
transformation of energy takes place with the aim of creating a jet of air exiting the engine at
high speed, thus allowing the propulsion of the aircraft according to the principle of
action/reaction. This transformation is achieved by a controlled variation of the cross-section of
the outlet tube.
In the case of Concorde (a now discontinued supersonic civil transport aircraft) and in the case of
a number of military aircrafts, a final transformation of energy, afterburning, is made in the
outlet tube. The principle of this transformation is to inject extra kerosene and burning the
mixture. The extra energy obtained gives an even higher
Speed to the jet of air exiting the engine and hence an even great propulsive power. A photo of
the outlet jet, with after burn shown in fig. This technology is mainly used for aircraft flying at
speeds greater than the speed of soun
6. Jet Propulsion
Jet propulsion is thrust produced by passing a jet of matter (typically air or water) in the opposite
direction to the direction of motion. By Newton's third law, the moving body is propelled in the
opposite direction to the jet. It is most commonly used in the jet engine, but is also the favoured
means of propulsion used to power various space craft.
A number of animals, including Cephalopods Sea hares, arthropods, and fish have convergently
evolved jet propulsion mechanisms.
Jet propulsion is most effective when the Reynolds number is high - that is, the object being
propelled is relatively large and passing through a low-viscosity medium.
In biology, the most efficient jets are pulsed, rather than continuous. at least when the Reynolds
number is greater than 6.
A jet engine is a reaction engine that discharges a fast moving jet of fluid to generate thrust by jet
propulsion and in accordance with Newton's laws of motion.

16. 15
6.1 Turbojets
The turbojet is an air breathing jet engine, usually used in aircraft. It consists of a gas turbine
with a propelling nozzle. The gas turbine has an air inlet, a compressor, a combustion chamber,
and a turbine (that drives the compressor). The compressed air from the compressor is heated by
the fuel in the combustion chamber and then allowed to expand through the turbine. The turbine
exhaust is then expanded in the propelling nozzle where it is accelerated to high speed to provide
thrust. Two engineers, Frank Whittle in the United Kingdom and Hans von Ohlin in Germany,
developed the concept independently into practical engines during the late 1930s. Turbojets have
been replaced in slower aircraft by turboprops which use less fuel. At medium speeds, where the
propeller is no longer efficient, turboprops have been replaced by turbofans.
The turbofan is quieter and uses less fuel than the turbojet. Turbojets are still common in
medium range cruise, due to their high exhaust speed, small frontal area, and relative simplicity.
The jet engine is only efficient at high vehicle speeds, which limits their usefulness apart from
aircraft. Turbojet engines have been used in isolated cases to power vehicles other than aircraft,
typically for attempts on land speed records. Where vehicles are 'turbine powered' this is more
commonly by use of a turbo shaft engine, a development of the gas turbine engine where an
additional turbine is used to drive a rotating output shaft. These are common in helicopters and
hovercraft. Turbojets have also been used experimentally to clear snow from switches in rail
yards.
Fig-f-turbojets

17. 16
6.2 Ramjet
A ramjet, sometimes referred to as a flying stovepipe or an athodyd (an abbreviation of aero
thermodynamic duct), is a form of air breathing jet engine that uses the engine's forward motion
to compress incoming air without an axial compressor. Ramjets cannot produce thrust at zero
airspeed; they cannot move an aircraft from a standstill. A ramjet-powered vehicle, therefore,
requires an assisted take-off like a rocket assist to accelerate it to a speed where it begins to
produce thrust. Ramjets work most efficiently at supersonic speeds around Mach 3 (2,284 mph;
3,675 km/h). This type of engine can operate up to speeds of Mach 6 (4,567 mph; 7,350 km/h).
Ramjets can be particularly useful in applications requiring a small and simple mechanism for
high-speed use, such as missiles. Weapon designers are looking to use ramjet technology in
artillery shells to give added range; a 120 mm mortar shell, if assisted by a ramjet, is thought to
be able to attain a range of 35 km (22 mi).They have also been used successfully, though not
efficiently, as tip jets on the end of helicopter rotors.
Ramjets differ from pulsejets, which use an intermittent combustion; ramjets employ a
continuous combustion process.
As speed increases, the efficiency of a ramjet starts to drop as the air temperature in the inlet
increases due to compression. As the inlet temperature gets closer to the exhaust temperature,
less energy can be extracted in the form of thrust. To produce a usable amount of thrust at yet
higher speeds, the ramjet must be modified so that the incoming air is not compressed (and
therefore heated) nearly as much. This means that the air flowing through the combustion
chamber is still moving very fast (relative to the engine), in fact it will be supersonic - hence the
name Supersonic Combustion Ramjet, or Scramjet.
Fig-g-aRamjet

18. 17
6.3 Rocket
A rocket engine is a type of jet engine that uses only stored rocket propellant mass for forming
its high speed propulsive jet. Rocket engines are reaction engines, obtaining thrust in accordance
with Newton's third law. Most rocket engines are internal combustion engines, although non-
combusting forms (such as cold gas thrusters) also exist. Vehicles propelled by rocket engines
are commonly called rockets. Since they need no external material to form their jet, rocket
engines can perform in a vacuum and thus can be used to propel spacecraft and ballistic missiles.
Rocket engines as a group have the highest thrust, are by far the lightest, but are the least
propellant efficient (have the lowest specific impulse) of all types of jet engines. The ideal
exhaust is hydrogen, the lightest of all gases, but chemical rockets produce a mix of heavier
species, reducing the exhaust velocity. Rocket engines become more efficient at high velocities
(due to greater propulsive efficiency and Oberth effect). Since they do not benefit from, or use,
air, they are well suited for uses in space and the high atmosphere.
Rocket engines produce thrust by the expulsion of an exhaust fluid which has been accelerated to
a high speed through a propelling nozzle. The fluid is usually a gas created by high pressure
(150-to-2,900-pound-per-square-inch (10 to 200 bar)) combustion of solid or liquid propellants,
consisting of fuel and oxidiser components, within a combustion chamber. The nozzle uses the
heat energy released by expansion of the gas to accelerate the exhaust to very high (supersonic)
speed, and the reaction to this pushes the engine in the opposite direction. Combustion is most
frequently used for practical rockets, as high temperatures and pressures are desirable for the best
performance, permitting a longer nozzle, giving higher exhaust speeds and better thermodynamic
efficiency.
An alternative to combustion is the water rocket, which uses water pressurised by compressed
air, carbon dioxide, nitrogen, or manual pumping, for model rocketry.
Rocket propellant is mass that is stored, usually in some form of propellant tank, prior to being
ejected from a rocket engine in the form of a fluid jet to produce thrust. Chemical rocket
propellants are most commonly used, which undergo exothermic chemical reactions which
produce hot gas which is used by a rocket for propulsive purposes. Alternatively, a chemically

19. 18
inert reaction mass can be heated using a high-energy power source via a heat exchanger, and
then no combustion chamber is used.
Solid rocket propellants are prepared as a mixture of fuel and oxidising components called 'grain'
and the propellant storage casing effectively becomes the combustion chamber. Liquid-fuelled
rockets typically pump separate fuel and oxidiser components into the combustion chamber,
where they mix and burn. Hybrid rocket engines use a combination of solid and liquid or gaseous
propellants. Both liquid and hybrid rockets use injectors to introduce the propellant into the
chamber. These are often an array of simple jets - holes through which the propellant escapes
under pressure; but sometimes may be more complex spray nozzles. When two or more
propellants are injected, the jets usually deliberately cause the propellants to collide as this
breaks up the flow into smaller droplets that burn more easily.
Fig-h- Rocket engine

20. 19
7. Conclusion
A propulsion system is a machine that produces thrust to push an object forward. On airplanes,
thrust is usually generated through some application of Newton's third law of action and reaction.
A gas, or working fluid, is accelerated by the engine, and the reaction to this acceleration
produces a force on the engine.
The four basic parts of a jet engine are the compressor, turbine, combustion chamber, and
propelling nozzles. Air is compressed, then led through chambers where its volume is increased
by the heat of fuel combustion. On emergence it spins the compression rotors, which in turn act
on the incoming air.

21. 20
8. References
1- Thermodynamics by P. K. Nag
2- Engineering Thermodynamics by R. K. Rajput
3- http://www.grc.nasa.gov
4- https://spaceflightsystems.grc.nasa.gov
5- https://en.wikipedia.org
6- Preliminary survey of propulsion using chemical energy stored in the upper atmosphere by
lionel v, baldwin and perry l. Blackshear
7- "A Century of Ramjet Propulsion Technology Evolution", AIAA Journal of Propulsion and
Power, Vol. 20, No. 1, January – February 2004.
8- Wake, M.H. (1993). "The Skull as a Locomotors Organ". In Hanken, James.The Skull.
University of Chicago Press.