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Saturday, April 30, 2016

Snippet: What is a Ramjet? (3 of n)

Design



A typical ramjet

A ramjet is designed around its inlet. An object moving at high speed through air generates a high pressure region upstream. A ramjet uses this high pressure in front of the engine to force air through the tube, where it is heated by combusting some of it with fuel. It is then passed through a nozzle to accelerate it to supersonic speeds. This acceleration gives the ramjet forward thrust.

A ramjet is sometimes referred to as a 'flying stovepipe', a very simple device comprising an air intake, a combustor, and a nozzle.

Normally, the only moving parts are those within the turbopump, which pumps the fuel to the combustor in a liquid-fuel ramjet. Solid-fuel ramjets are even simpler.

By way of comparison, a turbojet uses a gas turbine-driven fan to compress the air further. This gives greater compression and efficiency and far more power at low speeds, where the ram effect is weak, but is also more complex, heavier and expensive, and the temperature limits of the turbine section limit the top speed and thrust at high speed.


Courtesy: Wiki

Friday, April 29, 2016

Strangest Planes From Around The World

5 Strangest Military Airplanes

Snippet: What is a Ramjet? (2 of n)

Ramjets can be particularly useful in applications requiring a small and simple mechanism for high-speed use, such as missiles.
 
Weapon designers are looking to use ramjet technology in artillery shells to give added range; a 120 mm mortar shell, if assisted by a ramjet, is thought to be able to attain a range of 35 km (22 mi). They have also been used successfully, though not efficiently, on the end of helicopter rotors.
 
As speed increases, the efficiency of a ramjet starts to drop as the air temperature in the inlet increases due to compression. As the inlet temperature gets closer to the exhaust temperature, less energy can be extracted in the form of thrust.
 
To produce a usable amount of thrust at yet higher speeds, the ramjet must be modified so that the incoming air is not compressed (and therefore heated) nearly as much. This means that the air flowing through the combustion chamber is still moving very fast (relative to the engine), in fact it will be supersonic - hence the name Supersonic Combustion Ramjet, or Scramjet.


 
Check the video out beyond 2 minutes.


Courtesy: Wikipedia and Youtube

Thursday, April 28, 2016

Snippet: What is a Ramjet? (1 of n)

A ramjet, is a form of jet engine that uses the engine's forward motion to compress incoming air without a compressor. Ramjets cannot produce thrust at zero airspeed; they cannot move an aircraft from a standstill.
 
A ramjet-powered vehicle, therefore, requires an assisted take-off like a rocket assist to accelerate it to a speed where it begins to produce thrust.
 
Ramjets work most efficiently at supersonic speeds around Mach 3 (2,284 mph; 3,675 km/h). This type of engine can operate up to speeds of Mach 6 (4,567 mph; 7,350 km/h).




Courtesy: Wikipedia and Youtube

US Navy X47B STEALTH Unmanned Air Combat Vehicle aircraft