MECHANICAL ENGINEERING SEMINAR PRESENTATION ON “ JET ENGINE” Presented By :

1. MECHANICAL ENGINEERING SEMINAR PRESENTATION ON “ JET ENGINE” Presented By: Sagar Kumar Pattnaik 8th Semester, Regd No- 0601222357 Department of Mechanical Engineering

2. JET ENGINE 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 . This broad definition of jet engines includes turbojets, turbofans, rocket, ramjets , pulsejets and pump-jets, but in common usage, the term generally refers to a gas turbine Brayton cycle engine, an engine with a rotary compressor powered by a turbine.

3. HISTORY Timeline of Jet Power- * Jet engines can be dated back to the first century AD, when Hero of Alexandria invented the aeolipile. It was simply considered a curiosity. * Jet propulsion -Invention of the rocket by the Chinese in the 11th century. * In Ottoman Turkey in 1633 Lagari Hasan Çelebi a cone shape rocket was invented. * For Army Dr.Hans Von Ohain and Sir Frank Whittle are both recognized as being the co- inventors of the Jet Engine.

4. Ohain's jet was the first to fly in 1939.Frank Whittle's jet first flew in 1941.

5. Sir Frank Whittle(left) and  Dr.Hans Von Ohain

6. TYPES OF JET ENGINE *Water jet *Motorjet *Turbojet *Turbofan *Rocket *Ramjet *Turboprop, Turboshaft(similar) *Propfan/Unducted Fan *Pulsejet *Pulse detonation engine *Air-augmented rocket *Scramjet *Turborocket

7. WORKING OF JET ENGINE A Jet Engine operates on the application of Sir Isaac Newton's third law of physics: for every action there is an equal and opposite reaction. This is called thrust. Jet engines move the airplane forward with a great force that is produced by a tremendous thrust and causes the plane to fly very fast. All jet engines, which are also called gas turbines, work on the same principle. The engine sucks air in at the front with a fan. A compressor raises the pressure of the air. The compressor is made up of fans with many blades and attached to a shaft. The blades compress 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.

8. PARTS OF A JET ENGINE Fan- The fan is the first component in a turbofan. The large spinning fan sucks in large quantities of air. Most blades of the fan are made 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 the other jet engine components.

9. Compressor and Combustor 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. Combuster- In the combustor the 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 fuel catches fire. This provides a hightemperature, high-energy airflow.

10. Turbine and Nozzle 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. 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.

11. DIFFERENT TYPES OF JET ENGINE *Turbojet Engine- The Basic idea of the Turbojet Engine is simple. Air taken in from an opening in the front of the engine is compressed to 3 to 12 times its original pressure in compressor. Fuel is added to the air and burned in a combustion chamber to raise the temperature of the fluid mixture to about 1,100°F to 1,300° F. The resulting hot air is passed through a turbine, which drives the compressor. If the turbine and compressor are efficient, the pressure at the turbine discharge will be nearly twice the atmospheric pressure, and this excess pressure is sent to the nozzle to produce a high-velocity stream of gas which produces a thrust. Substantial increases in thrust can be obtained by employing an afterburner. It is a second combustion chamber positioned after the turbine and before the nozzle.

12. *Turboprop Jet Engine- A Turboprop Engine is a Jet Engine attached to a propellor. The turbine at the back is turned by the hot gases, and this turns a shaft that drives the propellor. Some small airliners and transport aircraft are powered by turboprops. Like the turbojet, the turboprop engine consists of a compressor, combustion chamber, and turbine, the air and gas pressure is used to run the turbine, which then creates power to drive the compressor. Compared with a turbojet engine, the turboprop has better propulsion efficiency at flight speeds below about 500 miles per hour.

13. *Turbofan Jet Engine- A Turbofan Engine has a large fan at the front, which sucks in air. Most of the air flows around the outside of the engine, making it quieter and giving more thrust at low speeds. Most of today's airliners are powered by turbofans. In a turbojet all the air entering the intake passes through the gas generator, which is composed of the compressor, combustion chamber, and turbine. In a turbofan engine only a portion of the incoming air goes into the combustion chamber. The remainder passes through a fan, or low-pressure compressor, and is ejected directly as a "cold" jet or mixed with the gas-generator exhaust to produce a "hot” jet.

14. *Turboshaft Engines- - This is another form of gas-turbine engine that operates much like a Turboprop System. It does not drive a propellor. Instead, it provides power for a helicopter rotor. The turboshaft engine is designed so that the speed of the helicopter rotor is independent of the rotating speed of the gas generator. This permits the rotor speed to be kept constant even when the speed of the generator is varied to modulate the amount of power produced.

15. *Ramjets- The most simple jet engine has no moving parts. The speed of the jet "rams" or forces air into the engine. It is essentially a turbojet in which rotating machinery has been omitted. Its application is restricted by the fact that its compression ratio depends wholly on forward speed. The ramjet develops no static thrust and very little thrust in general below the speed of sound. As a consequence, a ramjet vehicle requires some form of assisted takeoff, such as another aircraft. It has been used primarily in guided-missile systems. Space vehicles use this type of jet.

16. CONCLUSION Jet engines can be dated back to the first century AD. The patent for a stationary turbine was granted to John Barber in England in 1791. The broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets and pump-jets, but in common usage, the term generally refers to a gas turbine Brayton cycle engine, Most jet engines are internal combustion engines By the 1960s all large civilian aircraft were also jet powered, The ascension of the jet engine to almost universal use in aircraft took well under twenty years. The turboprop has a wide rotating fan that takes and accelerates the large mass of air but only till the limited speed of any propeller driven airplane. When the plane speed exceeds this limit, propellers no longer provide any thrust.The turbojets and other similar engines accelerate much smaller mass of the air and burned fuel, but they emit it at the much higher speeds possible with a de Laval nozzle. This is why they are suitable for supersonic and higher speeds.

17. The propulsive efficiency is highest when the engine emits an exhaust jet at a speed that is the same as the airplane velocity.Rocket engines are best suited for high speeds and altitudes. Rocket engines are more efficient than even scramjets. A turbojet engine is a type of internal combustion engine often used to propel aircraft. If the jet velocity exceeds the aircraft flight velocity, there is a net forward thrust upon the airframe. The efficiency of a jet engine is strongly dependent upon the overall pressure ratio and the turbine inlet temperature of the cycle. Turbojet engines take a relatively small mass of air and accelerate it by a large amount, whereas a propeller takes a large mass of air and accelerates it by a small amount. The high-speed exhaust of a turbojet engine makes it efficient at high speeds (especially supersonic speeds) and high altitudes. Very small aircraft generally use conventional piston engines to drive a propeller Most modern jet engines are actually turbofans, where the low pressure compressor acts as a fan. Turbofans are used for airliners because they give an exhaust speed that is better matched to subsonic airliner's flight speed, In the 1960s there was little difference between civil and military jet engines.Today's military turbofans, however, have a relatively high specific thrust, to maximize the thrust for a given frontal area, jet noise being of less concern in military uses relative to civil uses.  

18. THANK YOU VERY MUCH