Ramjet

Operation

The ramjet consists of a tube open at the two ends, into which one injects a Carburant which mixes with the Air. It ignites thanks to an ignition system then combustion is then maintained using devices called " hang flammes". The result of this Combustion is the production of hot gases in great quantity, which accelerate while slackening in the Tuyère finishing the engine, causing a significant Poussée.

In spite of the apparent simplicity of the concept, the effectiveness of such an engine depends largely on the interior shapes of the “tube”. The first part, known as air intake, makes it possible to compress the air (Théorème of Bernoulli) by lowering its speed. This deceleration is also accompanied by a heating of the air. The air thus arrives in the combustion chamber with a pressure and a high Température and a reduced Speed. This zone is equipped in general with several crowns of Injecteur S which pulverize the Carburant and maintain the Flamme. The shape of this room and the provision of the injectors must ensure the stability of the flame and the quality of combustion and constitute the most complex part to develop. Lastly, as for any other reaction engine, the shape of the conduit generates the push by Détente gases flarings. Thermal energy is transformed into kinetic energy.

This engine with the advantage of not comprising any machine element moving. It on the other hand has the disadvantage of not being able to function at null speed. It must thus be coupled to another system of propulsion to reach its minimal speed of operation, which limits its field of application considerably.

The term “ramjet” usually indicates the traditional ramjet, or ramjet with subsonic combustion. In this type of ramjet, the air velocity in the combustion chamber is largely subsonic, about Mach 0,5. But beyond a certain external speed, the lowering speed necessary becomes too important and the effectiveness of the engine decrease. This limit is between Mach 5 and 6. To solve this problem, combustion must be carried out in mode Supersonique. One speaks then about ramjet with supersonic combustion or Superstato engine or scramjet. Between Mach 3 and Mach approximately 6, the traditional ramjet is the most effective engine. In lower part of Mach 3, it becomes less effective than the Turboréacteur with simple flow.

Scope of application

The great nations study this system of propulsion with various successes.

The shortly after the Second world war, one believed, in particular in France, in the future of the ramjet. Rene Leduc built his planes “Leduc” which hardly shone by their performances and appeared difficult to control, the ramjet badly supporting the changes of rate of injection. More succeeded, the interceptor with turbo mixed propulsion/stato Northern Aviation 1500 “Griffon” exceeded Mach 2 between 1957 and 1959. But the development of the turbojets, much less constraining, put an end to the career of the ramjet. In 1960, the Air force and the Custom Air Force tested the flying target French CT41 which was equipped with two ramjets and which could reach Mach 3,1. Too much fast for its time, no plane which cannot intercept it, it for what it had been conceived, it was thus abandoned in 1965. Today, one finds ramjets with accelerators with powder integrated in supersonic Missile S like the ASMP.

With the the United States, NASA and the US Air Force manufactured several apparatuses functioning with a ramjet including one Drone of trisonic recognition in the years 1960. The Blackbird uses engines private individual, which includes/understands a turbojet surrounded by a ramjet, which ensures an increasing share of thorough out of high speed, a little as in the griffon.

An engine of the future?

Research on the Superstato engines, which are ramjets with supersonic combustion which use the oxygen contained in the air for combustion, and not in tanks, like the rockets, is promising. In spite of major defects (thermal problems, output with high-speeds) one hopes to be able to reach Mach number very high, about 10. Concepts proposing to use successively a rocket motor for an initial acceleration, then a ramjet (subsonic combustion), a superstatoreactor (supersonic combustion) and finally again a rocket to leave the atmosphere are studied. The general idea is to use the oxygen contained in the air during acceleration in the atmosphere, until Mach 10 to 12, to save on the oxygen mass classically embarked by a rocket and thus to gain in useful mass (satellite) which could transport the system. The validity of the concept is not shown yet.

External bonds

the saga of the ramjets
HyShot exceeded Mach 8
Quebec Distributeur of ramjets

Random links:

An open secret | Direction-of-Brittany | Yves Amyot | Pierre Guidoni | Bertold V of Zähringen