Jet engine



Jet Engine 3048
Photo by: arquiplay77

A jet engine is a heat engine that is propelled in a forward direction as the result of the escape of hot gases from the rear of the engine. In an airbreathing jet engine, air entering the front of the engine is used to burn a fuel within the engine, producing the hot gases needed for propulsion (forward movement). Jet engines are used for the fastest commercial and military aircraft now available.

A cutaway of a turbojet engine. A jet engine works by sucking air into one end, compressing it, mixing it with fuel and burning it in the combustion chanber, and then expelling it with great force out the exhaust system. (Reproduced by permission of The Gale Group.)
A cutaway of a turbojet engine. A jet engine works by sucking air into one end, compressing it, mixing it with fuel and burning it in the combustion chanber, and then expelling it with great force out the exhaust system. (Reproduced by permission of
The Gale Group
.)

Scientific principle behind jet engines

The scientific principle on which the jet engine operates was first stated in scientific terms by English physicist and mathematician Isaac Newton (1642–1727) in 1687. According to Newton's third law of motion, for every action there is an equal and opposite reaction. That principle can be illustrated by the behavior of a balloon filled with air. If the neck of the balloon is untied, gases begin to escape from the balloon. The escape of gases from the balloon is, in Newton's terms, an "action." The equal and opposite reaction resulting from the escape of gases is the movement of the balloon in a direction opposite to that of the movement of the gases. That is, as the air moves to the rear, the balloon moves forward.

Words to Know

Afterburner: A device added at the rear of a jet engine that adds additional fuel to the exhaust gases, increasing the efficiency of the engine's combustion.

Combustion: The process of burning; a chemical reaction, especially a rapid combination with oxygen, accompanied by heat and light.

Compress: To make more compact by using pressure.

Ramjet: A simple type of air-breathing jet engine in which incoming air is compressed and used to burn a jet fuel such as kerosene.

Turbojet: A type of air-breathing jet engine in which some of the exhaust gases produced in the engine are used to operate a compressor by which incoming air is reduced in volume and increased in pressure.

Turboprop: An engine in which an air-breathing jet engine is used to power a conventional propeller-driven aircraft.

Types of jet engines

Ramjets. The simplest of all jet engines is the ramjet. The ramjet consists of a long cylindrical metal tube open at both ends. The tube bulges in the middle and tapers off at both ends. As the engine moves forward at high speeds, the air entering it is automatically compressed (made more compact under pressure). The compressed air is then used to burn a fuel, usually a kerosene-like material. The hot gases produced during combustion within the engine are then expelled out the back of the engine. As the gases leave the back of the jet engine (the nozzle exit), they propel the engine—and the wing and airplane to which it is attached—in a forward direction.

A typical ramjet engine today has a length of about 13 feet (4 meters), a diameter of about 39 inches (1 meter), and a weight of about 1,000 pounds (450 kilograms). A ramjet engine of this design is capable of giving a maximum velocity of about Mach 4 (Mach 1 is equal to the speed of sound: 740 miles [1190 kilometers] per hour).

A jet aircraft with the engine cover open. (Reproduced by permission of Photo Researchers, Inc.)
A jet aircraft with the engine cover open. (Reproduced by permission of
Photo Researchers, Inc.
)

Turbojets. A turbojet differs from a ramjet in that it contains a compressor attached to a turbine. The compressor consists of several rows of metal blades attached to a central shaft. The shaft, in turn, is attached to a turbine at the rear of the compressor. When air enters the inlet of a turbojet engine, some of it is directed to the core of the engine where the compressor is located. The compressor reduces the volume of the air and sends it into the combustion chamber under high pressure.

The exhaust gases formed in the combustion chamber have two functions. They exit the rear of the chamber, as in a ramjet, providing the engine with a forward thrust. At the same time, the gases pass over the blades of the turbine, causing it to spin on its axis. The spinning turbine operates the compressor at the front of the engine, making possible the continued compression of new incoming air. Unlike a ramjet engine, which only operates after a high speed has been attained, the turbojet engine operates continuously.

Turboprop engines. In a turboprop engine, a conventional propeller is attached to the turbine in a turbojet engine. As the turbine is turned by the series of reactions described above, it turns the airplane's propeller. Much greater propeller speeds can be attained by this combination than are possible with simple piston-driven propeller planes. However, propellers cannot operate at high air speeds. The maximum efficient speed at which turboprop airplanes can operate is less than 450 miles (724 kilometers) per hour.

Afterburners. No more than about one-quarter of all the oxygen entering the front of the jet engine is actually used to burn fuel within the engine. To make the process more efficient, some jet engines are also equipped with an afterburner. The afterburner is located directly behind the turbine in the jet engine. It consists of tubes out of which fuel is sprayed into the hot exhaust gases exiting the tubing. Combustion takes place in the afterburner, as it does in the combustion chamber, providing the engine with additional thrust.



Also read article about Jet Engine from Wikipedia

User Contributions:

1
vishwas
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Apr 19, 2007 @ 2:02 am
ITS REALLY GOOD TO FIND A WEBSITE LIKE THIS, FROM WHICH JET ENTHUSIASTS LIKE US COME TO KNOW ABOUT THE WORKING IN DETAIL.
2
ananth krishna s
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Oct 31, 2007 @ 11:11 am
ITIS VERY USEFUL AERO ENGG. STUDENTS OF ANNNA UNIVERSITY, LANGUAGE USED IS VERY SIMPLE ,PLEASE ADD ABOUT SCRAM JET AND MORE INFORMATIONS
3
Promise
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May 22, 2008 @ 11:11 am
The article is very very nice and educative. Ca we also know the principle of the Aircraft brakes?
Thanks
4
Geevarghese
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Jun 17, 2008 @ 7:07 am
It is very good explanation for understanding Aircraft technology for any one.
5
christopher
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Jun 13, 2009 @ 12:00 am
Thanks very much for the idea and the information of the Aircrafts
engine
6
Allen
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Sep 25, 2009 @ 6:06 am
What metals and chemical used to make a jet engine???
7
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Aug 14, 2010 @ 10:10 am
hey nice piece of information i would like to visit ur site again
8
santosh
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Aug 19, 2010 @ 10:10 am
thanks yar i got so much information in this i thanks u all
9
PRANATHI
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Sep 24, 2010 @ 12:12 pm
THANK U FOR YOUR INFORMATION IT IS USEFULL FOR ALL SUBJECTS .
10
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Sep 30, 2010 @ 1:01 am
easy to understand, readable one to everyone.
make it up
11
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Jan 18, 2011 @ 7:19 pm
I'm researching the amount of oxygen per jet engine used. So far the numbers I'm given is the size of the engine equals the amount of oxygen assumed to be the burn ratio. But that doesn't seem right and wonder what that actual numbers are if there are any data to support the amount of oxygen burned say per hour or per minute?
12
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Mar 12, 2011 @ 1:01 am
it was usefull for me. i am going to prepare a ppt fpr seminar.
it is very much intresting
13
Nilesh
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Aug 18, 2011 @ 11:23 pm
How make mini jet plane in project?
Please give me some advice.
14
manish shrestha
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Dec 22, 2011 @ 11:23 pm
this jet engine model is good!in future i also want to fly such jet planes.i also want to design such jet engine!
15
Jaydeep
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May 24, 2012 @ 3:03 am
very nice information , by which we can understand how the jet engine works
16
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Jan 15, 2015 @ 4:16 pm
what is the chemical that makes jet to fry in the sky ?
17
jumbo sherpa
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Jul 16, 2015 @ 6:06 am
this is great site for the youngster which inspires to make changes areospace engineering in coming future
18
chidera okwaranyia
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Jul 21, 2015 @ 6:06 am
this is amazing i just love aeronautics and pages like this is what we need in this our world were facing today

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