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Pulse Detonation Engines (PDE's)



 
 
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  #11  
Old March 1st 04, 11:57 PM
Bruce Simpson
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On Sat, 28 Feb 2004 17:22:40 GMT, "Ed Majden"
wrote:


"Grantland" "Grantland"
Nope. Pulse-burn. Much less efficient.

Symantics! It was a pulse jet!




Fiesler Fi-103 (V1) Specifications

Engine: Argus pulse-jet
600 pounds of thrust
Length: 25' 4"
Wingspan: 17' 6"
Weight: 4800 lbs. Fully fueled
Fuel: 150 gallons of Acetylene gas
1 mile per gallon
Range: Approximately 160 miles from launch site
Performance: Speed between 360-400 mph
Flew at altitude of 2000-3000 ft
Average flight time of 22 minutes
Armament: 2337 pound war head

Not as efficient, but still an early prototype PULSE JET!!! Different
principal perhaps! Time marches on and so do design techniques.


Sorry but the V1 was not powered by acetylene -- they used very
low-grade gasoline. There would be no way to (safely) store sufficient
acetylene onboard even if they wanted to use it as a fuel.

Acetylene was used for starting in very cold weather but most
certainly never as a fuel.

--
you can contact me via http://aardvark.co.nz/contact/
  #14  
Old March 2nd 04, 01:57 AM
Felger Carbon
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"Bruce Simpson" wrote in message
...

There are significant problems to using PDEs as a propulsive source.
The magnitude of the shockwaves produced is extremely high as are

the
levels of vibration.

A craft using such a power-plant will need some very special

attention
paid to the acoustic and physical isolation of the engine.


Sounds like a micro-Orion. Now, there's an engine with _real_
acoustic and vibration problems! ;-)


  #16  
Old March 2nd 04, 06:13 AM
QDurham
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Dan wrote in part:
Hopefully not a detonation. That would be like slamming the piston face with a

sledge hammer. In fact it's a rapid combustion.

Amen. Detonation is exactly what octane is designed to prevent. The higher
the octane rating, the more resistant to detonation the fuel is.

I spent some time next to 3350 cubic inch engines which could be destroyed in
seconds by detonation -- even when using 130-145 octane fuel (purple and very
expensive.) Boost the manifold pressure, haul back on the RPM -- and the
engine might actually depart from the wing in a few seconds. Not recommended.

Quent


  #19  
Old March 2nd 04, 09:26 PM
Bruce Simpson
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On Mon, 1 Mar 2004 23:18:55 -0000, "Keith Willshaw"
wrote:


"Bruce Simpson" wrote in message
.. .
On 29 Feb 2004 18:57:36 -0800, (Eric Moore)


There are significant problems to using PDEs as a propulsive source.
The magnitude of the shockwaves produced is extremely high as are the
levels of vibration.

A craft using such a power-plant will need some very special attention
paid to the acoustic and physical isolation of the engine.


Hmmm

The British edition of scrap heap challenge recently had a program
in which teams had to build a jet propelled car.

The winner built a pulse jet and the 'high tech' isolation of engine
from vehicle seemed to consist of welding the bugger to the frame
though there was lots of duct tape in view


That was me -- I was the "expert" on that episode.

Fact is almost every motor car on the road runs with a
pulse detonation engine, its just that the pulse drives
a piston rather than being used for jet effect.


No, that's incorrect.

A conventional piston-engine does not detonate its fuel -- it uses a
process called deflagration which is a *far* gentler combustion
process.

It's also worth noting that a pulsejet (such as the one we used on
Scrapheap) also uses deflagration rather than detonation.

To give you an idea of the difference (in terms of shock, vibration
and noise) -- in a deflagration, the flame travels at just a few
meters per second, in a detonation the flame front effectively travels
at several times the speed of sound.

--
you can contact me via
http://aardvark.co.nz/contact/
  #20  
Old March 3rd 04, 05:16 AM
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Bruce Simpson wrote:


To give you an idea of the difference (in terms of shock, vibration
and noise) -- in a deflagration, the flame travels at just a few
meters per second, in a detonation the flame front effectively travels
at several times the speed of sound.


Yes, the operative word here is 'effectively' because there's
actually no defined flame-front at all. As the normal flame front
progresses across the firing chambre a certain area of the
remaining fuel/air charge starts getting squeezed (and heated by
it) till it's internal temperature arrives at it's ignition point
then the whole remaining area detonates almost instaneously
producing an extremely high spike of pressure which is
practically useless against the inertia of the piston/crank etc.
This spike quickly punches and burns holes in the piston etc.
--

-Gord.
 




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