h a l f b a k e r yAssume a hemispherical cow.
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A pulse jet in one of the more simple forms of a jet engine
and uses PDE. Using a miniaturised pulse jet (only
between 100mm and 200mm long) connected to a
generator power could be generated. The power from the
explosion producing the exhaust velocity would power a
turbine connected to the
mini generator. This would allow
a variety of fuels to be used in the generation of electricity
(alcohol diesel petrol etc), and the potential for
combustion of Hydrogen.
This idea is similar to the Jet Engine + Generator setup in
the new Jaguar so there is a real basis to the idea. This
differs in that the system would be tiny (small enough to
use on a bicycle).
Problems associated with this is the idea of the slowing
down of the air flow within the pulse jet due to the smaller
size. The air "sticks" to the side of the tube and as the
tube gets smaller the amount of air flowing through
unaffected with this "stickiness" reduces, posing the
problem that the pulse jet could potentially be choked off.
The second problem is that a pulse jet of this size would
have VERY low thrust so that generator would need to be
low geared for it to spin, and hope that the exhaust
velocity is great enough to produce viable generator spin
speeds.
Apart from these two problems I cannot see anymore
possible problems in the feasibility of this "halfbaked"
idea.
Mini Pulse Jet
http://www.youtube....watch?v=zn4YVYdp8lE
A video of a very small pulse jet working [qwertyuiop23, Jan 21 2011]
An Outburst Of Emulsion
An_20Outburst_20of_20Emulsion
Another terrible Bohemian Rhapsofy parody ... [8th of 7, Jan 23 2011]
[link]
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That should explode rather quickly. |
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Note: Added a link of a small pulse jet not exploding |
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I meant when it hit the fan. |
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... though I'll grant automotive turbochargers seem to do okay despite pulsed pressure. |
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And that a pulse jet would be used |
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Dammit! I hoped for a mind buckling Vernon idea |
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//Apart from these two problems I cannot see anymore
possible problem// Perhaps [FlyingToaster] overstates the
case, but he does raise what seems a legitimate third
problem: the stress on the turbine blades (there is a
turbine, yes?) and other components would have big spikes
in it -- peak values
would
be higher than in an ordinary generator, and there would
be
many, many cycles of strain-relief-strain. Would pose a
strength-of-materials problem, no? |
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I suppose the fact that this device has very low thrust is a
partial answer to this. But why is low-thrust pulse-jet
better than burning the same fuel in a continuous jet? It
sounds like you have an answer to that question in mind,
but could you explain it to us? |
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Pulse jets are quite noisy .... (the hint's in the
name). |
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The Argus type pulsejet on the V1 had a similar
problem of low specific impulse, hence the need for
a catapult launch. |
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[8th_of_7]//Pulse jets are quite noisy// Perzactly. I was
going to say: Any of the surviving
British pensioners
who remember the V1 will, on hearing this, immediately die
of a heart attack. Actually, to be precise, any of them who
hear the noise *stop* will instantly die of a heart attack. |
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So you suggest we start making them now so they are ready for 20 years time then? |
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I've always advocated using pulsejets as emergency engines on small aircraft: very light, very inexpensive. |
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Quickly going deaf while your tail is being set on fire could be the preferable option in many cases. |
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Actually, I was quite disappointed by the YouTube video.
The engine is mounted on what looks like fairly thin, stiff
wire. If it had any decent thrust, it would surely have bent
this mounting. What's the efficiency of a pulse-jet in
generating thrust? |
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about 10% of a decent turbojet... could be increased to 25% by an augmenter and stuff. |
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Power density ... power density ... powerdensity ... |
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<al dente> calamari calamari calamari </al dente> |
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// calamari calamari calamari // |
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... let me go, Beelzebub has a platter keeping warm for me, for me, for me ! |
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Jutta,
Just bunned a guy,
Put my cursor on the bread
Meant to fishbone him instead
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Once you add a turbine to a pulse jet, haven't you lost most of the advantages over a turbojet? |
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To put it another way, once you have approached the complexity and weight of a turbojet, why not have its higher efficiency and lower noise too? |
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--Look up "Magnetohydronamics". This was a relevant fad a few decades ago... |
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" that should explode rather quickly " |
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