A PRESENTATION

ON JET ENGINE

KM. SHIVA KATIYARROLL NO.: CSJMA12001390289

MEE- 2K12

PRESENTED BY:

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.

Thrust is the forward force that pushes the engine and therefore the airplane forward.

“A rearward channeled explosion can propel a machine forward at a great speed.”

Fig.1. Jet Engine [5]

Introduction

Jet engine is nothing but a Gas turbine. It works under the principle of Newton’s third law It states that “For every acting force there is an equal and

opposite force”. Gas turbine operates like toy balloon

Fig.2. Toy balloon [1]

Working Principle

Jet Propulsion

Operating principle based on Newton’s laws of motion.

Fig.3. Newton’s 3rd law of motion [1]

VinletVexit

Propulsive Efficiency ηp = Vinlet + Vexit

2Vinlet

Propulsion means to push forward or drive an object forward.

History

DR . HANS VON OHAN SIR FRANK M. WHITTLE

Ohan’s jet was first to fly in 1939.

Frank’s jet flew first in 1941 however he had patent his idea in 1930.

Parts of jet engine

FAN COMPRESSOR COMBUSTOR TURBINE MIXER NOZZLE Fig.4. Parts of jet engine [2]

How a jet engine works ?

Fig.5. Working of jet engine [2]

“Strictly speaking, energy is not “consumed”, but rather is converted into different forms.”

How air flows through the engine ?

Fig.6. Air flow through the engine [2]

The image above shows how the air flows through the engine. The air goes through the core of the engine as well as around the core. This causes some of the air to be very hot and some to be cooler. The cooler air then mixes with the hot air at the engine exit area.

Continued . . .

AIR INTAKE

Sucked in by the compressor

COMPRESSOR

Compressor speed and temperature increases gradually

FUEL BURNER

Fuel is mixed with the air, and electric sparks light the air, causing it to combust.

COMBUSTION CHAMBER

The air is burnt. Increase in the temperature

of the air, thus increases the pressure inside the engine.

Continued . . .

TURBINE

Works like a windmill The blades gain energy from the hot gases moving past them. This movement is used to power the compressor.

JET PIPE AND PROPELLING NOZZLE

The hot air rushes out of the nozzle. High pressure Hot air rushes out at very high speed

Piston Engine vs Jet Engine

Unsteady flow

RATE OF MASS AND ENERGY FLOW IS NOT CONSTANT.

Steady flow

RATE OF FLOW OF MASS AND ENERGY IS CONSTANT.

Fig.7. Piston Engine [3] Fig.8. Gas turbine Engine [1]

Combustion chamber

Propeller shaftWork output

Fuel

Compressor Turbine

workingGas Turbine Plant Layout

Air in Exhaust

Fig.9. Open cycle gas turbine [3]

Fuel(Heat)

Shaft

Simplistic gas turbines working principles

1-2 Isentropic compression (in a compressor); h2-h1 = mCp(T2-T1)2-3 Constant pressure heat addition (in a combustor); h3-h2 = mCp(T3-T2)3-4 Isentropic expansion (in a turbine); h3-h4 = mCp(T3-T4)4-1 Constant pressure heat rejection

Fig.10. Ideal Brayton cycle [3]

1. Turbojet

The turbojet engine is a reaction engine.

Substantial increases in thrust can be obtained by employing an afterburner

Types of Jet Engine

Fig.11. Turbojet [5]

2. Turboprop

A turboprop engine is a jet engine attached to a propeller.

Modern turboprop engines are equipped with propellers that have a smaller diameter but a larger number of blades for efficient operation at much higher flight speeds

Fig.12. Turboprop [5]

3. Turbofan

The objective of this sort of bypass system is to increase thrust without increasing fuel consumption.

It achieves this by increasing the total air-mass flow and reducing the velocity within the same total energy supply.

Fig.13. Turbofan [5]

4. Ramjet

It has no moving parts.

Combustion occurs at subsonic speed of airflow. Guided-missile systems, in defense sector used this type of jet.

Fig.14. Ramjet [5]

Mach 0.8 to Mach 5, efficient at high speed (> Mach 2.0 )

5. Scramjet

Scramjet (Supersonic Combustion Ramjet) A variant of Ramjet Air-breathing jet engine where combustion occurs in supersonic airflow.

Fig.15. Scramjet [5]

Few mechanical parts, can operate at very high Mach numbers (Mach 8 to 15) with good efficiencies.

Air Temp.

Thru

st

Increasing AltitudeTh

rust

Troposphere

Stratosphere

Trop

opau

se

Factor Affecting Thrust

Flat Rating

Tft

Fig.16. Temp. effect on thrust [1]

Fig.17. Altitude effect on thrust [1]

Thru

st

Pressure

Continued…

Fig.19. Pressure effect on thrust [1] Fig.20. Airspeed effect on thrust [1]

Applications

IN AIRCRAFT- Fighter plane, Missiles, Rocket, Airplane. Jet propulsion, land and sea transport, racing car. The first use of the jet engine was to power military aircraft. The General electric company used a “turboprop” jet engine to

run an electric generator. The jet engine is not only used on aircraft but on boats, where

water jets are used to propel the boat forward. Normal type of jet engine is used for domestic purpose i.e.

Traveling, carrying goods etc.

Advantages

High power to weight ratio.Very high speed therefore saves times.Mechanical efficiency of jet engine is high as compared to I.C. engine.

High fuel consumption. It is difficult to design a turbine that will work in high temperature with high speed.

Thermal efficiency of Jet engine is low compared to IC engine.

Disadvantages

Conclusion

Jet engine works on laws of basic thermodynamics as steady flow energy equation and Brayton cycle empowering the thought that natural resources air can be used according to human mind for the benefit of world.

Ram type of jet engines is used only in Defence sector. Because it travels at supersonic speed and generally high level of training is required. Since it travels at such a high speed it cannot be used for traveling.

Net work output of a jet propulsion cycle is zero.

Future Vision

To develop materials that can withstand extremely high temperatures and stresses required by more powerful engines.

Future engineers will find many opportunities to develop engines with increased efficiency, reduced mass, and exotic materials. New fuels, reduced noise, and reductions in pollution a wait further study, testing, and design.

As NASA seeks to return humans to space, as air travel continues to expand, and as humans seek to fly higher, faster, and farther, propulsion will play a major role in the design for the vehicles of the future.

“Engineers and engine designers are never content to stop “pushing the envelope” in aviation propulsion.”

References

[1]. R.D. Flack, “Fundamentals of Jet Propulsion”, Cambridge University Press, 2005.

[2]. J.L. Kerrebrock, “Aircraft Engines and Gas Turbines”, MIT Press, 1992.

[3]. R.K. Rajput, “Thermal Engineering”, Laxmi Publications, 9th edition, 2013, 754-795.

[4]. Y. A. Cengel and M. A. Boles. “Thermodynamics”, Mc Graw Hill, 7th edition, 2011, 484-535, 844-893.

[5]. H.Cohen, G.F.C. Rogers, and H.I.H. Saravanamutto, “Gas Turbine Theory”, 5th edition, New York: Wiley, 2003.

Thank you