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Butane/Oxygen/Hydrogen mix?

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Butane/Oxygen/Hydrogen mix?

Unread postAuthor: Alster370 » Thu Oct 13, 2011 1:57 pm

Im considering using Oxygen when I come around to building my hybrid cartridges, but the only way to get hydrogen (In my current situation) is to obtain it from my electrolysis cell. So I would get a ~2:1 mix of hydrogen and oxygen as my cell cannot separate the gases. So when Having a cartridge mix of butane/oxygen/hydrogen what would be the benefits/drawbacks?keeping in mind the hydrogen oxygen ratio cant be changed, (but can be pressurised to some extent) and the volume of butane could also be changed.

Cheers :D
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Last edited by Alster370 on Sun Oct 30, 2011 5:00 am, edited 1 time in total.
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Unread postAuthor: Labtecpower » Thu Oct 13, 2011 2:08 pm

I think you need DYI for this :roll:

I have GasEQ, but I have to find out to use it.

Maybe the butane will act like a buffer gas, wich isn't helping with performance, as it is pretty heavy. If the oxygen reacts with the butane, it will up the performance, as you have hydrogen as a buffer gas, wich is very light and has a high SOS

BTW, this one shot with hydrogen/oxygen/butane No calculations for how much of each gas was added, it was a ghetto gun after all :P

[youtube]http://www.youtube.com/watch?v=EBei3GXCm1w[/youtube]
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Unread postAuthor: Alster370 » Thu Oct 13, 2011 2:48 pm

I tried to do this with gaseq, but my chemistry knowledge only goes so far :D I thought that the addition of hydrogen to the O2/butane mix would reduce pressure, but increasing flame speed & the capable projectile speeds?

Ive seen that video, very impressive despite the the ghetto-ness :wink:
I didn't however know that you were running butane, in the HY/OX mix. How did the power change with and without the butane?
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Unread postAuthor: Labtecpower » Thu Oct 13, 2011 2:57 pm

I just started taping, and added the larger top tube for more power, but it accidentally looked a bit too nice and shiny :D

With only H2/O2 in the chamber it gave a BANG! that freaked out parents and pets, but almost no power.
When I added the butane I got a slightly duller sound, but more power. It shot through both sides of the box with a paper and ducttape dart.

I guess i'm just not gifted with the same brain as DYI :D
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Unread postAuthor: Alster370 » Thu Oct 13, 2011 3:11 pm

With only H2/O2 in the chamber it gave a BANG! that freaked out parents and pets, but almost no power.

You just need to pressurise it :D I would feel reasonably safe with pressurising it to 15-20psi, providing the cartridge was grounded to prevent static sparks :wink:

I know that with low mixes, butane will make a significant difference in performance, but at higher mixes, (6x+) my projectiles will be around 1000fps, so having at least some hydrogen in the chamber will make sure the efficiency doesn't drop as fast, as the projectile speed increases.

Btw, what projectile were you using? airsoft bb? chamber vol? barrel length?
(Im trying to establish what kind of enery your gun was producing :D)
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Unread postAuthor: saefroch » Thu Oct 13, 2011 3:51 pm

My GasEQ work tells me that starting with that 2:1 Hydrogen:Oxygen mix, you'd want a 2:1:0.21 mix of Hydrogen:Oxygen:Butane. That mix will produce 13.048atm, whereas without the butane it only yields 9.787atm. I highly suggest getting an accurate metering system and going for the butane addition.

EDIT: Compare that to the 9.636atm that I can squeeze out of a propane-air mixture. Yeah, I thought so. Use butane.

EDITx2: Just read your above comment. This could be totally epic. Your propellant gases will be roughly 50.3% H<sub>2</sub>, 27%H<sub>2</sub>O , 20%CO, 1.4%CO<sub>2</sub>, and about 1.1%OH.
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Unread postAuthor: Labtecpower » Fri Oct 14, 2011 12:09 am

Projectile: dart. weight: 5-10 grams?

Chamber vol: about 50 ccm

Barrel length: 30 cm


Another good thing about the mixture was the ease of ignition. A sloppy lighter piezo could ingnite it.
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Unread postAuthor: saefroch » Fri Oct 14, 2011 6:57 am

Did you try the mix that I suggested?
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Unread postAuthor: Alster370 » Fri Oct 14, 2011 7:18 am

Not yet, I'm at school :D I wont be able to try it till my syringes arrive next Tuesday so for now this thread is more of a discussion for now :lol: :oops:
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Unread postAuthor: saefroch » Fri Oct 14, 2011 9:17 am

That was aimed more at Labtec, but okay :)
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Unread postAuthor: DYI » Fri Oct 14, 2011 9:19 am

Looks like Saefroch beat me to this one. His ratio's right in the optimal pressure range for a butane/hydrogen/oxygen mix with the H<sub>2</sub> : O<sub>2</sub> the OP specified, but I'm getting a different value for the pressure; around 12.55 atm for this mix (which I worked out to be 0.23:2:1) rather than 13.05 atm. Oddly, the maximum pressure I found for propane/air was almost exactly the same.

Either way, this mix is superior to pure 1:2 oxygen/hydrogen for a given pre-ignition pressure, and actually results in a higher sound speed as well, of about 1600 m/s (compare to 1550 m/s for 1:2 oxygen/hydrogen).
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Unread postAuthor: Labtecpower » Fri Oct 14, 2011 9:59 am

Did you try the mix that I suggested?


Nope, granddad is at our house. Altough he is a bit deaf, i'm not doing any loud experiments until sunday :D

I guess fueling will just be purging the chamber with the gas out of my electrolysis cell after it vented all the air, and then adding butane?

I think some hydrogen may be lost during the process.. I guess an aluminium foil BD would be the best?
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Unread postAuthor: saefroch » Fri Oct 14, 2011 11:34 am

I think we just found that my simulation is slightly superior to DYI's :D

Did you include all species including oxygen and nitrogen, the HO radical, and all hydrocarbons with 4 or less carbons?

I just re-tried the simulation, maxed out the product species, .23 butane gives me 13.016atm, hardly a measurable difference, but inferior to the .21 mix.
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Unread postAuthor: Alster370 » Fri Oct 14, 2011 11:51 am

Do your results count for the air already present in the cartridge?
To be fair that "1000fps with 6x mix" was with butane and air not oxygen, so hopefully I can achieve 1000fps at about a 3.5-4x mix with bu/hy/ox, not bad eh? :lol:

I think as far as fuelling goes it will have to be done with a syringe, given the small chamber volume.
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Unread postAuthor: SpudBlaster15 » Fri Oct 14, 2011 1:17 pm

DYI and saefroch: Which value did you use for the initial temperature of the reactants?

The default temperature of 300K gives numbers more in line with DYI's simulation, but I can approximate saefroch's results by dropping the starting conditions to 288K (15C). Using the extended product set appears to have no effect on the final pressure.

As for the 2:1:0.21 mixture itself, I'd like to see some testing done on the burning properties of such a fuel rich composition. Given the relative concentrations of oxygen and hydrogen in the mix, I suspect the burn rate will still be high enough to be usable, but it's difficult to make assumptions without any data.
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