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basicelectromechanic
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The range of flammability ( by proportion ) of hydrogen air mixtures is much greater than the comparatively narrow range of gasoline air mixtures.
Should a fuel leak occur with a H2 powered vehicle in an enclosed space like a parking garage and a source of ignition be handy the result could be
disastrous.
A punctured gasoline tank will spill flammable fuel, but won't BLEVE like a H2 filled pressure vessel.
On the bright side H2 is clean burning and roughly 30% more powerful per unit displacement for an internal combustion engine.
Ignition temperature of H2 and air mix compressed is much higher than the gasoline counterpart, higher compression ratios are possible without
preignition problems. The higher specific heat and latent heat of a hydrogen rich ( versus carbon )fuel results in lower peak temperatures ( but that
latent heat can be in issue with respect to efficiency).
I read a great book on the subject of alternative fuels as a child, so many years have passed I cannot remember the title ( sorry ). Much of the
material was translated from German and much of the research took place during WWII. Those guys did wild research, experimenting with just about
anything that burns, building engines with glass cylinder heads ( allowing high speed photography of flame propagation)...
Given the history and military significance of petroleum this is not surprising.
[Edited on 6-12-2004 by basicelectromechanic]
[Edited on 6-12-2004 by basicelectromechanic]
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oxydiser
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Aye, but in saying that the concept of a hydrogen economy seems distant. Current technology using metal hydrides (eg. palladium) only release the
stored H2 at ~473K which means shitty efficiency and fuel cell catalyst poisoning in polluted cities is no good either. The H-car would only work
(read: be economically viable) in really clean places (iceland as mentioned) with cheap cheap electricity (think canada eh? with all that hydroelectric power).
Yes hydrogen cars will only take off after the oil starts to run out... wait a sec that has already started to happen
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tetrachloromethane
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| Quote: |
A punctured gasoline tank will spill flammable fuel, but won't BLEVE like a H2 filled pressure vessel.
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A compressed hydrogen tank at room temperature contains no liquid hydrogen. Therefore, there is no phase change taking place if H2 leaks, and a BLEVE
(Boiling Liquid Expanding Vapor Explosion) would definitely not occur.
That doesn't necessarily mean that there would not be a huge explosion.
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froot
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If you have a mixture of hydrogen and oxygen you will get a detonation if it is even slightly confined. In fact I read from an old book called the
'Van Nortrands Scientific Encyclopedia' that the VOD of H2 and O2 mixture can be greater than that of nitroglycerin. I'm not sure how
credible that is but in my dumb days I used to set off party balloons with a mixture of O2 and C2H2. They were incredibly loud, and hydrogen is worse.
So a hydrogen leak in a confined area like a garage is a recipe for disaster.
We salute the improvement of the human genome by honoring those who remove themselves from it.
Of necessity, this honor is generally bestowed posthumously. - www.darwinawards.com |
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12AX7
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Gasoline in an enclosed volume is pretty dangerous, too. 
Acetylene very readily detonates because of the molecule's instability (C2H2 = 2C + H2 + who knows how much enthalpy). Matter of fact, you
can't compress it more than 15PSI (1bar) at room temperature before it gets dangerous.
Hydrogen is different, I guess. Depending on pressure I'd think it can detonate pretty well too, but if engines can run it, it must be okay.
Hmm, platinum sparkplugs are a no-no
Tim
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Nerro
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I may be parrotting someone here but the intended storage method for the hydrogen is as a hydride salt so even when the fuel tank(s) of a
hydrogenvehicle is/are punctured they will not vent hydrogen gas (at any dangerous rate anyway )
#261501 +(11351)- [X]
the \"bishop\" came to our church today
he was a fucken impostor
never once moved diagonally
courtesy of bash
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IrC
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"I may be parrotting someone here but the intended storage method for the hydrogen is as a hydride salt so even when the fuel tank(s) of a
hydrogenvehicle is/are punctured they will not vent hydrogen gas (at any dangerous rate anyway"
Which hydride? I have 25 gm KH which would explode if water contacted it, and this is a given in a real wreck. I also have 4 pounds of calcium
hydride, maybe that is safer. Just fire mostly if it gets wet. The United Nuclear link is interesting, read it while I was buying 100 gm heavy water
(still hoping for cold fusion or useful fusors). They appear to have a well tested working system but leave many questions. Such as, gee, when I
charge up my fuel at home do I go out and scoop a shovelful of charged hydride into the top like a Mr Fusion? Do I need an umbrella on a rainy day? Ok
you hook up a hose but still, on long trips would I need to tow a trailer to bring the generator along for the ride? Think I'll try one on my
SUV.
"Hmm, platinum sparkplugs are a no-no"
That sucks 12AX7, I just bought new platinum plugs!
25 gm KH? Don't ask, I have no use for it, will never need it and really don't want it around but I had to buy it to get the Lithium
Aluminum Hydride that was part of the sale.
As to Palladium Hydride, look at the size of the 4 tanks at the U.N. site. If I had that much Pd I would sell it and buy a gas guzzling Hemi Cuda.
Obviously the hydride involved is something else.
One other thing I noticed at U.N. is suddenly the U238 is gone. Unlike the I2, where they have a discontinued notice, DU just vanished. I wonder which
governmental agency made them pull that. Glad I got 36 gm of it while I could!
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kyanite
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A safer source than metal hydrides
Why store it, when you can make it on the spot? Of course you can't have
every car using this technology, but this could be used in small power source or something? Remarkably simple, you take aluminium powder, add a salt
solution, grind(what you're after is to bend/stretch/squeeze the Al), and collect the hydrogen. Apparently theres a company in Vancouver trying
to see if this is actually useable right now.
[Edited on 23-7-2005 by kyanite]
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12AX7
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OMFG... wow, I can't believe that even came up. That's almost hilarious it's so dense. I mean, so what do you do with the three
valence electrons at -1.676V?
Make heat?
Tim
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