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#11
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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/ |
#13
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"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 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. Keith |
#14
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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! ;-) |
#15
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From: "Keith Willshaw" 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. Keith Hopefully not a detonation. That would be like slamming the piston face with a sledge hammer. In fact it's a rapid combustion. Dan, U.S. Air Force, retired |
#16
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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 |
#17
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(B2431) wrote:
From: "Keith Willshaw" 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. Keith Hopefully not a detonation. That would be like slamming the piston face with a sledge hammer. In fact it's a rapid combustion. Dan, U.S. Air Force, retired Most damned absolutely correct. It seems that damned near everyone thinks otherwise. I've heard supposedly experienced and knowledgeable mechanics say "You'll see a power rise during detonation", when in fact the powerful blasts of detonation are so shortlived that they produce almost no useful energy. (lots of destructive energy though) -- -Gord. |
#18
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#19
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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
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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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