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Gas Things

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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Unread postAuthor: LucyInTheSky » Sun Jan 07, 2007 12:24 pm

Heres a site comparing different gases, I have nothing else to say so enjoy.

http://www.bernzomatic.com/bernzomatic/ ... sons.jhtml
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Unread postAuthor: Deko » Sun Jan 07, 2007 12:44 pm

thats pretty sweet thanks for that site :D
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Unread postAuthor: Bluetooth » Sun Jan 07, 2007 1:03 pm

Wow! Acetylene requires very little oxygen.
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Unread postAuthor: squeaks » Sun Jan 07, 2007 1:06 pm

Well, this is kinda usefull except that it tells us everything that we already knew-butane is weaker than propane which is weaker than mapp which is weaker than acetylene. It would be interesting to get some comparisons like this on different gases though. Nice find.
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Unread postAuthor: Bluetooth » Sun Jan 07, 2007 1:12 pm

It's still useful though.
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Unread postAuthor: mark.f » Sun Jan 07, 2007 1:25 pm

I'd like to see the same chart with these included as well:

Propylene
Ethylene
Propadiene
Isopropyl alcohol, (properly vaporized)

and many others.
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Unread postAuthor: benstern » Sun Jan 07, 2007 1:31 pm

How the hell did they find out the vapor pressure of acetylene to be 250 psi?
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Unread postAuthor: SpudBlaster15 » Sun Jan 07, 2007 1:42 pm

squeaks wrote:Well, this is kinda usefull except that it tells us everything that we already knew-butane is weaker than propane which is weaker than mapp which is weaker than acetylene. It would be interesting to get some comparisons like this on different gases though. Nice find.


Butane actual has a higher energy content per unit of volume than propane, it is just more difficult to meter and more expensive.
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Unread postAuthor: beebs111 » Sun Jan 07, 2007 2:07 pm

although the flame temp is hotter by 400 degrees, the burning velocity of propane is much higher, thus it burns faster blah blah blah
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Unread postAuthor: SpudBlaster15 » Sun Jan 07, 2007 3:03 pm

The flame propogation rate in air differs by about 10%, and such a difference is irrelevant when it concerns our use. The difference between the fuels comes from the available energy content of each, which is influenced by the carbon to hydrogen ratio. In the case of butane, more carbon dioxide will form as opposed to water, and CO2 has a much lower heat of vaporization, meaning more energy can be released in the form of heat, leading to greater expansion.
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Unread postAuthor: boilingleadbath » Sun Jan 07, 2007 4:37 pm

...I figured you guys would compare them.

Butane:
C4H10 + 6.5 O2 -> 4 CO2 + 5 H2O
(7.5 -> 9)
With a flame temperature of 3200*F, this gives us a flame pressure of 7.1 times the inital pressure.

Propane:
C3H8 + 5 O2 -> 3 CO2 + 4 H2O
(6 -> 7)
With flame temperature of 3450*F, this gives us a flame pressure of 7.3x.

That's a difference of less than 3 psi in a typical combustion cannon.
Practicaly the same, if you ask me.
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