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Oxyhydrogen as a 'exhaust-less' fuel

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Oxyhydrogen as a 'exhaust-less' fuel

Unread postAuthor: cammyd32 » Wed Mar 27, 2013 4:37 pm

I have recently been reading up on 'Oxyhydrogen and it's effectiveness as a combustion fuel.
Oxyhydrogen is a mixture of gasses and can be created straight from water (to put it simply, I know there is more stages involved) but surely this means that the gas produced is already at the correct ratio for a complete combustion, without any secondary mixing or agitating?
Also because the two components of oxyhydrogen, when ignited, mix together to create water, doesn't this mean that also the chamber has no residual 'exhaust gasses' which have to be vented etc?

I have seen people use it in cannons and launchers in a few places around the interwebs, and some searching on the site has shown that it is quite effective, two things that interest me especially are how small chambers have to be to attain a good power, and also it's lack of any need for mixing+venting of the chamber before and after firing.
So my question is: why do we not see more people use this gas in combustion cannons? especially those who are making semi's, because surely the lack of a need to vent the chamber or use metering equipment to achieve a perfect reliable mix should make the gas a prime candidate for someone who wants simplicity and reliability above all?

Now my understanding of chemistry is pretty much capped at A level chemistry so I'm hoping that someone will have more knowledge on this than me, so Is there something that I don't know about that explains why the gas is not used as much?
Cheers,
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Unread postAuthor: Labtecpower » Wed Mar 27, 2013 4:49 pm

Using a stochiometric mixture of hydrogen and oxygen isn't interesting for spudding purposes, as the pressure it generates isn't very high.
In order for it to be useable, you need to include a buffer gas.
To keep the SOS in your working fluid as high as possible this would ideally be an excess amount of hydrogen, or helium.
In a spudgun you won't need exotic gases, so nitrogen would be good :D

I believe there's a gasEQ chart floating around somewhere about including propane in the mixture, wich gave significantly higher pressures.

[Youtube]http://m.youtube.com/#/watch?v=EBei3GXCm1w&desktop_uri=%2Fwatch%3Fv%3DEBei3GXCm1w[/youtube]
Link isn't doing what I want it to do, just click it :roll:
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Unread postAuthor: cammyd32 » Thu Mar 28, 2013 11:04 am

http://www.youtube.com/watch?v=w-RIb48J55I
http://www.youtube.com/watch?v=b4rgfvQGnHs
http://www.youtube.com/watch?v=nIq-g9vaecw

What were you saying about it not being powerful? :wink:
Okay, okay, I know the loud bangs in the last video were mainly due to the way in which it burns quickly, and the others had rather large chambers, but still, although not as powerful as butane/and/or/propane it still seems to pack quite a bit of punch, enough for smaller + lighter projectiles surely?

But seriously, apart from that, is everything else that I said 'technically' true? about the venting fueling etc? I need to know if I'm wasting my time looking into this,
Thanks
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Unread postAuthor: Technician1002 » Thu Mar 28, 2013 11:54 am

The Hydrogen Oxygen mix burns very fast, so generation of a shock-wave is common (loud bang) but being lighter gases, they very quickly lose heat to the chamber resulting in very quick drop in temperature and pressure, so unless you are shooting ping pong balls, your spuds will fly slower as the push on the spud will be of short duration. Try plugging the gas into GGDT. Note without a buffer gas you will have a higher Oxygen and Fuel content than a fuel air mix. Straight Oxygen Hydrogen is very explosive.

This is how fast the stuff burns..
[youtube]http://www.youtube.com/watch?v=MMB2VR0087w[/youtube]
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Unread postAuthor: cammyd32 » Fri Mar 29, 2013 11:53 am

Okay then, the addition of a buffer gas to get 'usable' power will probably complicate things to an extent where the benefits of using oxyhydrogen will no longer make that much of a difference, thanks for the replies folks.
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