This document provides an overview of gas turbine engines. It discusses the history of gas turbine engines, including early developments in England, Germany, and the United States. It then describes the basic process of how gas turbine engines work, including the compressor, combustion chamber, and turbine. Finally, it discusses the different types of gas turbine engines, such as centrifugal flow, axial flow, and centrifugal-axial flow engines.

1. Topic: Gas Turbine Engines.
Submitted By:
Guide:
College:
Year: 20 – 20

2. Seminar Approval Sheet:
The seminar report entitled “Gas Turbine
Engines” by is approved for the degree of Auto
Mobile Polytechnique.
XYZ XYZ
(Head of Mechanical Dept.) (Examiner) (Guide)

3. ACKNOWLEDGEMENT
Though it may appear the following “Eulogizing “exposition of monotonous
beat of an usual acknowledgement. I assert, beyond the confines of the simple
sense of the word “Gratitude.” I size this opportunity to pass on my deep felt thanks
to those who have helped me
I express my deep sense of gratitude towards my able and acknowledge
guide ___________ whose guidance and constant inspiration led me towards the
completion of the seminar work.
I thank my colleagues for their cooperation in making this seminar a success.
Your name

4. Abstract
The name GAS TURBINE means exactly what it says. A turbine type engine
that is operated by gas rather than one operated, for instance, by steam or water.
The gas, which operates the turbine, is the product of the combustion that takes
place when a suitable fuel is mixed and burned with the air passing through the
engine.
The seminar includes the working process of gas turbine engines, its types
and characteristics and its applications in military aircrafts.
Advantage of gas turbine engines over reciprocating engines forms the
concluding part.
A neutral view has been taken by including the disadvantages as well.

5. Index:
Sr. No. Title Page No.
1 Abstract. 01
2 Introduction. 02
3 History 03
4 Gas Turbine 06
5 Gas Turbine Process 07
6
Gas Turbine Engine
 Centrifugal flow.
 Axial flow.
 Centrifugal-Axial flow.
11
7 Engine Theory 17
Advantages & Disadvantages 23
8
9 Conclusion 25
10 References 26

6. Introduction
There are many different kinds of turbines:
· You have probably heard of a steam turbine. Most power plants use
coal, natural gas, oil or a nuclear reactor to create steam. The steam runs through a
huge and very carefully designed multi-stage turbine to spin an output shaft that
drives the plant's generator.
· Hydroelectric dams use water turbines in the same way to generate
power. The turbines used in a hydroelectric plant look completely different from a
steam turbine because water is so much denser (and slower moving) than steam,
but it is the same principle.
· Wind turbines, also known as windmills, use the wind as their motive
force. A wind turbine looks nothing like a steam turbine or a water turbine because
winds is slow moving and very light, but again, the principle is the same.
A gas turbine is an extension of the same concept. In a gas turbine, a pressurized gas
spins the turbine. In all modern gas turbine engines, the engine produces its own pressurized
gas, and it does this by burning something like propane, natural gas, and kerosene or jet fuel.
The heat that comes from burning the fuel expands air, and the high-speed rush of this hot air
spins the turbine.

7. HISTORY
England
Sir Frank Whittle: Whittle is considered by many to be the father of the jet engine.
In 1930 Frank Whittle submitted his patent application for a jet aircraft engine.
The first Whittle engine was called the Power Jet W.1, after its manufacturer.
It flew in the British Gloster G.40 on May 15, 1941 with W 1 Whittle engine installed.
Germany

8. VON OHAIN At the same time, von Ohain in Germany had been at work on
the development of a jet engine for aircraft. He built and ran his first demonstration
engine in 1937. His first flight engine was the HES 3B which used on HE178 and
flew on August 27, 1939.
The Whittle and the von Ohain engines led to successful jet-powered fighter
aircraft by the end of World War II, the Messerschmitt Me262 that was used by
German Air Force.
It might be note that the early English production jet engine used centrifugal
compressor where as the production engine in Germany employed the more
advanced axial flow compressor.
America
America was a latecomer to the jet-propulsion field and with the help of British
Government; the General Electric Corporation was awarded the contract to built W.1
an American Version. The first jet engine airplane in America was made in October

9. 1942, in Bell XP-59A. The two General Electric I-A engines used in this airplane, the
I-A engine was rated at about 1300 lb of thrust. In late 1941, NAVY awarded the
contract to Westinghouse. Westinghouse engineers designed an engine with an
axial compressor and an annular combustion chamber. Shortly thereafter, several
other companies began to design and produce gas turbine engines.
Gas Turbine
As the principle of the gas turbine, a working
gas (air) is compressed by a compressor and
heated by combustion energy of the fuel at the first.
The working gas becomes the high temperature
and high pressure. The engine converts the energy
of working gas into the rotating energy of the
blades, making use of the interaction between the gas and the blades.

10. As shown in the below figure, there are two types of the gas turbine. One is
the open cycle type (internal type), and another is the closed cycle type (external
type). Basic components of both types are the air compressor, a combustor and the
turbine.
The gas turbine can handle a larger gas flow than that of the reciprocating
internal combustion engines, because it utilizes a continued combustion. Then the
gas turbine is suitable as the high power engine. The gas turbine for airplanes
(called a jet engine) makes use of this advantage.
The Gas Turbine Process
Gas turbine engines are, theoretically, extremely simple. They have three parts:
· Compressor - Compresses the incoming air to high pressure
· Combustion area - Burns the fuel and produces high-pressure, high-velocity
gas
· Turbine - Extracts the energy from the high-pressure, high-velocity gas
flowing from the combustion chamber
The following figure shows the general layout of an axial-flow gas turbine -- the sort of
engine you would find driving the rotor of a helicopter, for example:

11. In this engine, air is sucked in from the right by the compressor. The
compressor is basically a cone-shaped cylinder with small fan blades attached in
rows (eight rows of blades are represented here). Assuming the light blue represents
air at normal air pressure, then as the air is forced through the compression stage its
pressure rises significantly. In some engines, the pressure of the air can rise by a
factor of 30. The high-pressure air produced by the compressor is shown in dark
blue.
This high-pressure air then enters the combustion area, where a ring of fuel
injectors injects a steady stream of fuel. The fuel is generally kerosene, jet fuel,
propane or natural gas. If you think about how easy it is to blow a candle out, then
you can see the design problem in the combustion area -- entering this area is high-pressure
air moving at hundreds of miles per hour. You want to keep a flame burning
continuously in that environment. The piece that solves this problem is called a
"flame holder," or sometimes a "can." The can is a hollow, perforated piece of heavy
metal. Half of the can in cross-section is shown below:

12. The injectors are at the right. Compressed air enters through the
perforations. Exhaust gases exit at the left. You can see in the previous figure that a
second set of cylinders wraps around the inside and the outside of this perforated
can, guiding the compressed intake air into the perforations.
At the left of the engine is the turbine section. In this figure there are two sets
of turbines. The first set directly drives the compressor. The turbines, the shaft, and
the compressor all turn as a single unit:
At the far left is a final turbine stage, shown here with a single set of vanes. It
drives the output shaft. This final turbine stage and the output shaft are a completely
stand-alone, freewheeling unit. They spin freely without any connection to the rest of
the engine. And that is the amazing part about a gas turbine engine -- there is
enough energy in the hot gases blowing through the blades of that final output
turbine to generate 1,500 horsepower and drive a 63-ton M-1 Tank! A gas turbine
engine really is that simple.

13. In the case of the turbine used in a tank or a power plant, there really is
nothing to do with the exhaust gases but vent them through an exhaust pipe, as
shown. Sometimes the exhaust will run through some sort of heat exchanger either
to extract the heat for some other purpose or to preheat air before it enters the
combustion chamber.
The discussion here is obviously simplified a bit. For example, we have not
discussed the areas of bearings, oiling systems, internal support structures of the
engine, stator vanes and so on. All of these areas become major engineering
problems because of the tremendous temperatures, pressures and spin rates inside
the engine. But the basic principles described here govern all gas turbine engines
and help you to understand the basic layout and operation of the engine.

14. Gas Turbine Engine
The gas turbine engine runs on a Brayton cycle using a continuous
combustion process. In this cycle, a compressor (usually radial flow for automotive
applications) raises the pressure and temperature of the inlet air. The air is then
moved into the burner, where fuel is injected, and combusted to raise the
temperature of the air. Power is produced when the heated, high-pressure mixture is
expanded and cooled through a turbine. When a turbine engine is directly coupled to
a generator, it is often called a turbo generator or turbo alternator.
The power output of a turbine is controlled through the amount of fuel
injected into the burner. Many turbines have adjustable vanes and/or gearing
to decrease fuel consumption during partial load conditions and to improve
acceleration.
Most of modern passenger and military aircraft are powered by gas turbine
engines, which are also called jet engines. There are several types of jet engines,
but all jet engines have some parts in common. Aircraft gas turbine engines can be
classified according to (1) the type of compressor used and (2) power usage
produces by the engine.
Compressor types are as follows:
1. Centrifugal flow
2. Axial flow
3. Centrifugal-Axial flow.

15. Power usage produced is as follows:
1. Turbojet engines
2. Turbofan engines.
3. Turbo shaft engines.
Centrifugal Compressor Engines
Centrifugal flows engines are compress the air by accelerating air outward
perpendicular to the longitudinal axis of the machine. Centrifugal compressor
engines are divided into Single-Stage and Two-Stage compressor. The amount of
thrust is limited because the maximum compression ratio.
Principal Advantages of Centrifugal Compressor
1. Light Weight.
2. Simplicity.
3. Low cost.

16. Axial Flow Compressor Engines
Axial flow compressor engines may incorporate one, two, or three spools (Spool is
defined as a group of compressor stages rotating at the same speed). Two-spool
engine, the two rotors operate independently of one another. The turbine assembly
for the low-pressure compressor is the rear turbine unit. This set of turbines is
connected to the forward, low-pressure compressor by a shaft that passes through
the hollow center of the high-pressure compressor and turbine drive shaft.
Advantages and Disadvantages
Advantages:
Most of the larger turbine engines use this type of compressor
because of its ability to handle large volumes of airflow and high-pressure
ratio.

17. Disadvantages:
More susceptible to foreign object damage, Expensive to
manufacture and it is very heavy in comparison to the centrifugal
compressor with the same compression ratio.
Axial-Centrifugal Compressor Engine
Centrifugal compressor engine were used in many early jet engines, the
efficiency level of single stage centrifugal compressor is relatively low. The
multi-stage compressors are somewhat better, but still do not match with
axial flow compressors. Some small modern turbo-prop and turbo-shaft
engines achieve good results by using a combination axial flow and
centrifugal compressor such as PT6 Pratt and Whitney of Canada which
very popular in the market today and T53 Lycoming engine.
Characteristics and Applications

18. The turbojet engine: Turbojet engine derives its thrust by highly accelerating
a mass of air, all of which goes through the engine. Since a high “jet " velocity is
required to obtain an acceptable of thrust, the turbine of turbo jet is designed to
extract only enough power from the hot gas stream to drive the compressor and
accessories. All of the propulsive force (100% of thrust) produced by a jet engine
derived from exhaust gas.
The turboprop engine: Turboprop engine derives its propulsion by the
conversion of the majority of gas stream energy into mechanical power to drive the
compressor, accessories, and the propeller load. The shaft on which the turbine is
mounted drives the propeller through the propeller reduction gear system.
Approximately 90% of thrust comes from propeller and about only 10% comes from
exhaust gas.
The turbofan engine: Turbofan engine has a duct-enclosed fan mounted at
the front of the engine and driven either mechanically at the same speed as the
compressor, or by an independent turbine located to the rear of the compressor drive
turbine. The fan air can exit separately from the primary engine air, or it can be
ducted back to mix with the primary's air at the rear. Approximately more than 75%
of thrust comes from fan and less than 25% comes from exhaust gas.
The turbo shaft engine: Turbo shaft engine derives its propulsion by the
conversion of the majority of gas stream energy into mechanical power to
drive the compressor, accessories, just like the turboprop engine but the shaft
on which the turbine is mounted drives something other than an aircraft
propeller such as the rotor of a helicopter through the reduction gearbox. The
engine is called turbo shaft.

19. ENGINE THEORY
OPERATION
The jet engines are essentially a machine designed for the purpose of
producing high velocity gasses at the jet nozzle. The engine is started by rotating the
compressor with the starter, the outside air enter to the engine. The compressor
works on this incoming air and delivery it to the combustion or burner section with as
much as 12 times or more pressure the air had at the front. At the burner or
combustion section, the ignition is igniting the mixture of fuel and air in the
combustion chamber with one or more igniters which somewhat likes automobile
spark plugs. When the engine has started and its compressor is rotating at sufficient
speed, the starter and igniters are turn off. The engine will then run without further
assistance as long as fuel and air in the proper proportions continue to enter the
combustion chamber. Only 25% of the air is taking part in the actual combustion
process. The rest of the air is mixed with the products of combustion for cooling
before the gases enter the turbine wheel. The turbine extracts a major portion of
energy in the gas stream and uses this energy to turn the compressor and
accessories. The engine's thrust comes from taking a large mass of air in at the front
and expelling it at a much higher speed than it had when it entered the compressor.
Thrust, then, is equal to mass flow rate time’s change in velocity.

20. The more air that an engine can compress and use, the greater is the power or
thrust that it can produce. Roughly 75% of the power generated inside a jet engine is
used to drive the compressor. Only what is left over is available to produce the thrust
needed to propel the airplane.
JET ENGINE EQUATION
Since Fuel flow adds some mass to the air flowing through the engine, this
must be added to the basic of thrust equation. Some formulary does not consider the
fuel flow effect when computing thrust because the weight of air leakage is
approximately equal to the weight of fuel added. The following formulary is applied
when a nozzle of engine is " choked “; the pressure is such that the gases are
traveling through it at the speed of sound and cannot be further accelerated. Any
increase in internal engine pressure will pass out through the nozzle still in the form
of pressure. Even this pressure energy cannot turn into velocity energy but it is not
lost.

21. Factors Affecting Thrust
The Jet engine is much more sensitive to operating variables. Those are:
1. Engine rpm.
2. Size of nozzle area.
3. Weight of fuel flow.
4. Amount of air bled from the compressor.
5. Turbine inlet temperature.

22. 6. Speed of aircraft (ram pressure rise).
7. Temperature of the air.
8. Pressure of air
9. Amount of humidity.
Note; item 8, 9 are the density of air.
Engine Station Designations
Station designations are assigned to the various sections of gas turbine
engines to enable specific locations within the engine to be easily and accurately
identified. The station numbers coincide with position from front to rear of the engine
and are used as subscripts when designating different temperatures and pressures
at the front, rear, or inside of the engine. For engine configurations other than the
picture below should be made to manuals published by the engine manufacturer.
N = Speed (rpm or percent)
N1 = Low Compressor Speed
N2 = High Compressor Speed

23. N3 = Free Turbine Speed
P = Pressure
T = Temperature
T = Total
EGT = Exhaust Gas Temperature
EPR = Engine Pressure Ratio (Engine Thrust in term of EPR). Pt7 / Pt2
Ex.: Pt 2 = Total Pressure at Station 2 (low pressure compressor inlet)
Pt 7 = Total Pressure at Station 7 (turbine discharge total pressure)

24. Advantages
· The turbine is light and simple: -
The only moving part of a simple turbine is the rotor. A turbine has no
reciprocating motion, and consequently runs smoother than a reciprocating engine.
· A turbine will run on a variety of fuels: -
Any combustible fuel that can be injected into the airstream will burn in a
turbine. A turbine has this flexibility because the continuous combustion is not
heavily reliant on the combustion characteristics of the fuel.
· A turbine produces low levels of emissions: -
Because of its multi-fuel capability; a fuel, which burns completely and
cleanly, can be used to reduce emissions.
Disadvantages
The turbine engine has a few drawbacks, which have prevented its
widespread use in automotive applications:
· Turbine engines have high manufacturing costs: -
Because of the complicated design, manufacturing is expensive.

25. Conclusion:
Thus we have thoroughly gone through the gas turbine engine. The seminar
information shows the advantages, benefits, characteristics, and applications of gas
turbine engines.
It clearly states the superiority of gas turbine engines over reciprocating
engines. We have taken a neutral view of the topic.
Reference Text:
Following are the sources from where the information for the seminar has
been collected:
1. www.howstuffworks.com
2. www.thai-engines.com
3. www.gasturbineengines.com