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Turbojet

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A turbojet is an airbreathing jet engine used to power aircraft. It is a type of gas turbine engine that creates thrust to move a vehicle forward. This engine is essential for high-speed flight because it replaces traditional propellers with a high-speed jet of exhaust. While turbojets are less efficient at low speeds, they are perfect for supersonic travel. Today, they are still used in medium-range cruise missiles due to their simplicity and small frontal area.

JetEngineGraph2
JetEngineGraph2

The engine works through a specific sequence of steps to turn air into motion. First, air enters through an intake or tube. This intake directs air smoothly into the engine and helps manage pressure. Next, the air enters a compressor. The compressor uses rotating blades to squeeze the air into a smaller space, which increases its pressure and temperature.

Axial compressor
Axial compressor

After compression, the air moves into a combustion chamber. Here, fuel is mixed with the compressed air and burned. The resulting hot, expanding gases flow through a turbine. This turbine extracts energy from the gas to spin the compressor, keeping the cycle going. Finally, the remaining gas expands through a propelling nozzle. This nozzle accelerates the exhaust to a very high speed to provide thrust.

Turbojet operation- axial flow
Turbojet operation- axial flow

There are two main types of compressors used in these engines: centrifugal and axial. A centrifugal compressor, like the one used in early Whittle engines, throws the air outward from the center. An axial compressor, like the one in the Junkers Jumo 004, keeps the airflow parallel to the axis of thrust.

Jumo 004
Jumo 004

Most manufacturers eventually moved toward axial designs by the 1950s because they allow for a smaller engine diameter. While turbojets provide direct thrust, a related design called a turboshaft uses an extra turbine to drive a rotating shaft. Turboshafts are commonly used to power helicopters and hovercraft.

The history of the turbojet involves two engineers working independently in the late 1930s. In the United Kingdom, Frank Whittle developed the concept and filed his first patent in 1930. His team successfully ran the first liquid-fuelled Power Jets WU engine on 12 April 1937. In Germany, Hans von Ohain patented a similar engine in 1935. On 27 August 1939, the Heinkel He 178 became the first aircraft to fly using von Ohain's turbojet design.

Ohain USAF He 178 page61
Ohain USAF He 178 page61

In Britain, the Gloster E.28/39 made the first jet-engined flight in 1941.

Whittle Jet Engine W2-700
Whittle Jet Engine W2-700

By 1944, the first operational turbojet aircraft entered service. The Messerschmitt Me 262 entered service in April, while the Gloster Meteor followed in July. The Me 262 was produced in large numbers, with up to 1,400 units manufactured. These engines changed aviation by allowing much higher speeds than piston engines. However, early engines faced challenges with heat. Without advanced materials, early non-UK engines had to be overhauled every 10 to 20 hours to prevent damage. British engineers used Nimonic alloys to improve durability, allowing some engines to run for 500 hours without maintenance.

The development of high-temperature materials was vital for engine progress. Engineers had to create superalloys and cooling designs to handle the intense heat of the turbine. In the early days, pilots even had to monitor turbine temperatures manually to avoid damage. Some early engines used water injection during takeoff to increase thrust without exceeding temperature limits. This method increased thrust but often left a visible smoke trail because it prevented complete combustion. As technology improved, automatic temperature limiting was introduced to help pilots.

J85 ge 17a turbojet engine
J85 ge 17a turbojet engine

Turbojets had a massive impact on the reliability of commercial aviation. Older piston engines were less reliable, often requiring planes to carry four engines for safety. Turbojets can reach dispatch reliability ratings of over 99.9 percent. This high reliability allowed designers to build planes with only two or three engines. This change enabled more direct, long-distance flight paths. The Concorde is a famous example of a plane that used turbojets to maintain supersonic speeds.

Frank Whittle CH 011867
Frank Whittle CH 011867

Even at Mach 2.2, the engine efficiency of the Concorde helped manage the high drag of supersonic flight.

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🖼️ Images & Media (10)
File:Jumo 004.jpg
Jumo 004.jpg
File:JetEngineGraph2.PNG
JetEngineGraph2.PNG
File:Frank Whittle CH 011867.jpg
Frank Whittle CH 011867.jpg
File:Ohain.jpg
Ohain.jpg
File:Ohain USAF He 178 page61.jpg
Ohain USAF He 178 page61.jpg
File:Whittle Jet Engine W2-700.JPG
Whittle Jet Engine W2-700.JPG
File:J85 ge 17a turbojet engine.jpg
J85 ge 17a turbojet engine.jpg
File:Axial compressor.gif
Axial compressor.gif
File:Turbojet operation- centrifugal flow.png
Turbojet operation- centrifugal flow.png
File:Turbojet operation- axial flow.png
Turbojet operation- axial flow.png
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