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Author Topic: scramjet  (Read 3758 times)

Offline Dogboy

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scramjet
« on: 13/03/2008 22:24:03 »
I was wondering if you could power a scramjet engine with compressed air, and if so what sort of levels of compression would you need.  is there a way of to compress air without the tempature drop. 


 

another_someone

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scramjet
« Reply #1 on: 14/03/2008 03:10:52 »
Simple answer is no.

A scramjet is a hybrid engine, that is a modification of a ramjet (it stands for Supersonic Combustion Ramjet).  A ramjet is a form of internal combustion engine (and this is further emphasised by the fact that the scramjet modifies the combustion process).  Thus, you must have a combustion process of some sort for either a ramjet, or its derivative, the scramjet.  Compressed air is not a combustion process.

In any case, the hole purpose of a scramjet (and generally also true of ramjets) is to power an aircraft in supersonic flight, but you cannot get compressed air to travel supersonically, so you cannot get it to power a vehicle at supersonic speeds.
 

Offline Dogboy

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scramjet
« Reply #2 on: 14/03/2008 03:49:58 »
what is the limitation to getting compressed air to travel supersonic?
 

another_someone

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scramjet
« Reply #3 on: 14/03/2008 04:18:52 »
what is the limitation to getting compressed air to travel supersonic?

Sound is merely a series of compressed regions in the material (including air), and its speed is limited by how fast those compressed regions can travel through the material.  If a compressed region of the material were capable of travelling faster through the material, then the speed of sound would be higher (and for some materials it is higher, while for others it is lower).

You can get air to travel faster than sound, but only if you have an explosive force behind it (that is why explosions give a bang, which is the sonic boom created by the air in front being forced to travel at supersonic speeds).

I suppose you could get air to travel faster than sound by forcing it through a venturi tube, but you'd need a very large compressed air supply to have any meaningful thrust from such a device.
« Last Edit: 14/03/2008 04:25:32 by another_someone »
 

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scramjet
« Reply #3 on: 14/03/2008 04:18:52 »

 

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