How Different Types of Jet Engine Works PDF

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How Different Types of Jet Engines Work...

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GROUP # 15

HOW DIFFERENT TYPES OF JET ENGINE WORKS?

SUBMITTED TO:

H.M. YAZDAN ZUHAD

CLASS:

BS (2nd Year)

GROUP MEMBERS:

COURSE:

AEROSPACE (SST-401)

HUSNA NAZEER

DEPARTMENT:

ISST, UNIVERSITY OF KARACHI.

MARYAM ZEHRA

MAJOR DEPARTMENT: MATHEMATICS, UNIVERSITY OF KARACHI.

ANOUSHIA SHABBIR

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INDEX TOPICS

PAGE NUMBER

1. Introduction to jet engines

01

2. History

01

3. Fundamental equations governing jet engines 4. Types of engines

01-02

5. Turbojet

02-03

6. Turbofan

03-04

7. Turboprop

05-06

02

8. Afterburning turbojet

06

9. Ramjet

07

10. Scramjet

08

11. Ultra-high bypass

08

12. Conclusion

08

13. References

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IN INTRO TRO TROD DUC UCTIO TIO TION N TO JET EN ENGIN GIN GINES ES ES:: An engine using jet propulsion for forward thrust, mainly used for aircraft.Jet propulsion is defined simply as any forward movement caused by the backward ejection of a high-speed jet of gas or liquid. In the case of air travel and engines, jet propulsion means that the machine itself is powered by jet fuel.

HIS HISTO TO TORY: RY: The invention of the jet engine can be traced back to the aeolipile made around 150 B.C., Dr. Hans von Ohain and Sir Frank Whittle are both recognized as being the co-inventors of the jet engine as we know it today,

HANS VON OHAIN

FRANK WHITTLE

even though each worked separately and knew nothing of the other's work. While Von Ohain is considered the designer of the first operational turbojet engine, Whittle was first to register a patent for his schematics of a prototype, in 1930. Von Ohain obtained a patent for his prototype in 1936, and his jet was the first to fly in 1939. Whittle's took off for the first time in 1941. While von Ohain and Whittle may be the acknowledged fathers of modern jet engines, many grandfathers came before them, guiding them as they paved the way for the jet engines of today.

FU FUNDA NDA NDAME ME MENT NT NTAL AL EEQU QU QUAT AT ATION ION IONSS G GO OVER VERNI NI NING NG JET ENG ENGINE INE INES: S: THRUST PRODUCED IN THE ENTIRE JET ENGJINE: Most modern passenger and military aircraft are powered by gas turbine engines, which are also called jet engines. There are several different types of jet engines, but all jet engines have some parts in common. All jet engines have a nozzle which produces the thrust. Thrust is the force which moves an aircraft through the

𝑭 = 𝒎 𝒅𝒐𝒕 (𝑽𝒆 − 𝑽𝟎 )

air. Thrust is generated by the engines of the airplane. The most general thrust equation is then given by:

where; m dot = Mass Flow Rate Ve = Exit Velocity V0 = Free Stream Velocity

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The exit velocity of the nozzle performance is:

𝟏 (𝜸−𝟏)/𝜸 ) ] 𝑽𝒆 = 𝑽𝟖 = √𝟐𝒄𝒑 𝑻𝒕𝟖 𝜼𝒏[𝟏 − ( 𝑵𝑷𝑹 where; 𝑐𝑝 = Specific Heat 𝑇𝑡8 = Total Nozzle Exit Temperature 𝜂𝑛 = Adiabatic Nozzle Efficiency 𝑁𝑃𝑅 = Nozzle Pressure Ratio = pt8/p8 𝛾 = Specific Heat Ratio

TYPE TYPESS O OFF JET EN ENGIN GIN GINES: ES: There are various types of jet engines, some of them are listed below:       

Turbojet engine Turbofan engine Turboprop engine Afterburning turbojet engine Ramjet engine Scramjet engine Ultra high by-pass engine

1. TUR TURBO BO BOJE JE JET: T: The first and simplest type of gas turbine is the turbojet. It works on the principle of low mass and high acceleration.

CONSTRUCTION: A turbojet engine is a jet engine which produces all of its thrust by ejecting a high energy gas stream from the engine exhaust nozzle. The component parts of a turbojet engine are the inlet, the gas turbine engine, consisting of a compressor, a combustion chamber and a turbine, and the exhaust nozzle. 2

WORKING: Air is drawn into the engine through the inlet and compressed and heated by the compressor. Fuel is then added in the combustion chamber and ignited. The burning fuel adds energy to the exhaust stream by heating and expanding the air. A typical jet engine ratio has a 50:1 ratio of air mass flow to fuel mass flow. Now the hot expanding gas passes into the turbine. The turbine extracts sufficient energy to drive the compressor from the gases. The remainder of the exhaust energy is used to produce thrust, a process which is enhanced by the geometry of the exhaust nozzle. As the exhaust gas passes through the nozzle, it is accelerated to high speed as it expands thus providing propulsion.

2. TUR TURBO BO BOFAN FAN FAN:: Modern airliners use turbofan engines because of their high thrust and good fuel efficiency. A turbofan engine sometimes referred to as a fanjet or bypass engine, is the most modern variation of the basic gas turbine engine.

CONSTRUCTION: (Core engine: Every gas turbine engine has a combustion section (red), a compressor (cyan) and a turbine (magenta). The compressor, burner, and turbine are called the core of the engine, since all gas turbines have these components.) In the turbofan engine, the core engine is surrounded by a fan in the front and an additional turbine at the rear. The fan and fan turbine are composed of many blades, and are connected to an additional shaft.

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WORKING: The incoming air is captured by the engine inlet. Some of the incoming air passes through the fan and continues on into the core compressor and then the burner, where it is mixed with fuel and combustion occurs. The hot exhaust passes through the core and fan turbines and then out the nozzle, as in a basic turbojet. The rest of the incoming air passes through the fan and bypasses, or goes around the engine, just like the air through a propeller. The air that goes through the fan has a velocity that is slightly increased from free stream. So a turbofan gets some of its thrust from the core and some of its thrust from the fan. The ratio of the air that goes around the engine to the air that goes through the core is called the bypass ratio. A turbofan engine that derives most of its thrust from the jet engine core efflux is referred to as low bypass engine whereas an engine that derives most of its thrust from the fan is referred to as a high bypass engine. Low bypass engines are most commonly found in military applications, and may be equipped with an afterburner, whereas high bypass turbofan engines are the prevalent design in today’s commercial aviation jet engines. Because the fuel flow rate for the core is changed only a small amount by the addition of the fan, a turbofan generates more thrust for nearly the same amount of fuel used by the core. This means that a turbofan is very fuel efficient. That is why turbofans are found on high speed transports and propellers are used on low speed transports.

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3. TUR TURBO BO BOPRO PRO PROP: P: Many low speed transport aircraft and small commuter aircraft use turboprop propulsion. (Propulsion is the study of how to design an engine that will provide the thrust that is needed for a plane to take off and fly through the air. The engine provides the power for the airplane.)

CONSTRUCTION/WORKING: The turboprop uses a gas turbine core to turn a propeller. As, propeller engines develop thrust by moving a large mass of air through a small change in velocity. Propellers are very efficient and can use nearly any kind of engine to turn the prop. There are two main parts to a turboprop propulsion system, the core engine and the propeller. The core is very similar to a basic turbojet except that instead of expanding all the hot exhaust through the nozzle to produce thrust, most of the energy of the exhaust is used to turn the turbine. There may be an additional turbine stage present, which is connected to a drive shaft. The drive shaft, is connected to a gear box. The gear box is then connected to a propeller that produces most of the thrust. The exhaust velocity of a turboprop is low and contributes little thrust because most of the energy of the core exhaust has gone into turning the drive shaft. When the aircraft is used over relatively short distances, these cost and performance benefits offset the lower speed making turboprops the engine of choice for most commuter aircraft. Examples of turboprop powered aircraft include the Bombardier Dash 8, the Alenia ATR 42 and the Pilatus PC-12. A turboprop engine is very similar to a turboshaft and many engines are available in both variants. The principal difference between the two is that the turboprop version must be designed to support the loads of the attached propeller whereas a turboshaft engine need not be as robust as it normally drives a transmission which is structurally supported by the vehicle and not by the engine itself. (A turboshaft engine is a variant of a jet engine that has been optimized to produce shaft power to drive machinery instead of producing thrust. Turboshaft engines are

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most commonly used in applications that require a small, but powerful, light weight engine, inclusive of helicopters and auxiliary power units.)

4. AFT AFTER ER B BUR UR URNING NING NING:: An afterburner (or a reheat) is an additional component present on some jet engines, mostly military supersonic aircraft. Its purpose is to provide an increase in thrust, usually for supersonic flight, takeoff and for combat situations. Afterburning is achieved by injecting additional fuel into the jet pipe downstream of (i.e. after) the turbine. The nozzle of the basic turbojet has been extended and there is now a ring of flame holders, in the nozzle. The advantage of afterburning is significantly increased thrust; the disadvantage is its very high fuel consumption and inefficiency, though this is often regarded as acceptable for the short periods during which it is usually used. Jet engine thrust is governed by the general principle of mass flow rate. Thrust depends on two things: the velocity of the exhaust gas and the mass of that gas. A jet engine can produce more thrust by either accelerating the gas to a higher velocity or by having a greater mass of gas exit the engine. To generate the increased power with a more compact engine for short periods of time, an engine requires an afterburner. The afterburner increases thrust primarily by accelerating the exhaust gas to a higher velocity. While the mass of the fuel added to the exhaust does contribute to an increase in thrust, this effect is small compared to the increase in exhaust velocity.

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5. RAM RAMJET JET JET:: CONSTRUCTION: The ramjet is the most simple jet engine and has no moving parts. It is essentially a turbojet in which rotating machinery has been omitted. because of this simplicity, is often referred to as a "flying stovepipe". The engine consists of an air intake, a combustor and an exhaust nozzle.

WORKING: compressed by the forward speed of the aircraft itself or A high speed object moving through the air generates a high pressure region in front of it. The ramjet engine intake takes in high dynamic pressure air from this region and, using shockwaves created by the intake configuration, slows the air to subsonic speed before it enters the combustion chamber. In the combustor, fuel is mixed with the compressed air and ignited to reaccelerate the exhaust to supersonic speed. The exhaust gas is further accelerated as it exits the engine due to the geometric configuration of the exhaust nozzle.

Ramjets produce thrust only when the vehicle is already moving; ramjets cannot produce thrust when the engine is stationary or static. Since a ramjet cannot produce static thrust, some other propulsion system must be used to accelerate the vehicle to a speed where the ramjet begins to produce thrust. The higher the speed of the vehicle, the better a ramjet works until aerodynamic losses become a dominant factor. Ramjet propelled vehicles operate from about Mach 3 to Mach 6. 7

6. SCR SCRAM AM AMJET JET JET:: A scramjet engine is an improvement over the ramjet engine and it allows supersonic combustion. A scramjet (supersonic combustion ramjet) is a ramjet engine in which the airflow through the engine remains supersonic, or greater than the speed of sound. Scramjet powered vehicles are envisioned to operate at speeds up to at least Mach 15. Ground tests of scramjet combustors have shown this potential, but no flight tests have surpassed the Mach 9.6 X-43A flight.

7. ULT ULTRA RA H HIG IG IGH H BY-PA PASS SS EENG NG NGINE INE to improve fuel consumption, some ultra-high bypass engines are on the drawing board. As a rule: the higher the ratio, the more efficient the engine. And more efficient engines mean lower fuel consumption and emissions. Ultra high bypass technology has the potential for significant reductions in fuel burn, noise and emissions. A recently developed engine layout, identified as the inducted fan (or UDF; trademark), provides a set of very high-efficiency counter-rotating propeller blades, each blade mounted on one of either of two sets of counter-rotating low-pressure turbine stages and achieving all the advantages of the arrangement without the use of a gearbox.

CO CONCLU NCLU NCLUSI SI SION ON ON:: Jet engines have in general a high technological level but there are demands on lower fuel consumption and reduced pollutant emissions. To achieve this alternate thermodynamic cycles recovering the thermal energy of the exhaust gas are considered. Heat exchanged jet engines are in the line of developments that may lead to improved performance and contribution to the overall optimization of jet engines.

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REFERENCES 

https://www.thoughtco.com/history-of-the-jet-engine4067905#:~:text=While%20Von%20Ohain%20is%20considered,the%20first%20time%20in%201941.

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https://en.wikipedia.org/wiki/Jet_engine#/media/File:Jet_engine.svg

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https://www.skybrary.aero/index.php/Turbojet_Engine#:~:text=A%20turbojet%20engine%20is%20a ,from%20the%20engine%20exhaust%20nozzle.&text=Air%20is%20drawn%20into%20the,the%20co mbustion%20chamber%20and%20ignited.

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https://www.grc.nasa.gov/www/k-12/airplane/aturbf.html

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https://www.skybrary.aero/index.php/Turbofan_Engine

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https://www.skybrary.aero/index.php/Turboprop_Engine

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https://www.grc.nasa.gov/WWW/k-12/airplane/aturbp.html

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https://www.skybrary.aero/index.php/Afterburner



https://www.grc.nasa.gov/www/k-12/airplane/aturba.html



https://www.thoughtco.com/different-types-of-jet-engines-1992017

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https://www.britannica.com/technology/jet-engine/Turboprops-propfans-and-unducted-fanengines

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https://www.isro.gov.in/launchers/isro%E2%80%99s-scramjet-engine-technologydemonstratorsuccessfully-flight-tested

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https://www.skybrary.aero/index.php/Ramjet



https://www.grc.nasa.gov/www/k-12/airplane/ramjet.html

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https://www.nasa.gov/centers/langley/news/factsheets/X43A_2006_5.html#:~:text=A%20scramjet %20(supersonic%2Dcombustion%20ramjet,to%20at%20least%20Mach%2015.&text=In%20a %20scramjet%2C%20even%20the%20airflow%20through%20the%20engine%20remains%20s upersonic.

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