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Butane/Oxygen/Hydrogen mix?

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Unread postAuthor: DYI » Fri Oct 14, 2011 2:22 pm

SpudBlaster's right, we've probably used different starting temperatures.

I was thinking the same thing regarding the rich mixes - looking at a 2:5 C<sub>3</sub>H<sub>6</sub> / O<sub>2</sub> mixture, a starting pressure of 1 atm gives an adiabatic combustion pressure of 23 atm, and a sound speed of over 1400m/s. I'm interested enough that I think I'll run some tests with this mix over the Christmas break. It should be considerably less prone to detonations than my current mixes, and require a lower fueling pressure.

I suppose it's never been mentioned because when high speed hybrids are mentioned, hydrogen and helium immediately come to mind. The intentional production of CO instead of CO<sub>2</sub>, and the excess hydrogen which isn't bound up in water makes perfect sense from a SOS optimization standpoint.

Looks like this is just the motivation I needed to finish off that miniature 200X hybrid chamber...
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Unread postAuthor: saefroch » Fri Oct 14, 2011 2:59 pm

I also used a staring temp of 300K... but I just checked my list of reactants and realized I stuck in 1.3moles of C<sub>4</sub>H<sub>6</sub>.

Wait... just ran simulation again, no change as a result. I'm still getting 13.048atm and 1,638.5m/s SOS.

With the SOS I just produced, wouldn't it be more practical to use the Butane/Oxygen/Hydrogen mix? After all, you can crank up the pressure by increasing the mix number, but not the SOS...

EDIT: I pulled a 24.346atm, 1468.2m/s configuration out of a 2:1 Oxygen:Propene mix

Are you not including OH and O in your simulations as products?
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Unread postAuthor: DYI » Fri Oct 14, 2011 3:21 pm

Which version of GasEq are you running? Your pressures, temperatures, and sound speeds for all the mixes you mentioned are higher than I'm getting.

I'm using v0.79, which appears to be the most recent. For the mix you mention in your edit, I get 23.1 atm, 1434.9 m/s SOS.

With the SOS I just produced, wouldn't it be more practical to use the Butane/Oxygen/Hydrogen mix? After all, you can crank up the pressure by increasing the mix number, but not the SOS...


I, unlike the OP, do not yet have a working electrolysis rig. I also don't currently have a high pressure oxygen source, and my only source of hydrogen gas is from chemical reactions, which I would then have to pressurize to make use of. I do, however, have oxygen at ~300psi and a large supply of propane and propylene. Also, while the statement about increasing pre-ignition pressure is correct, there's a lot to be said for "high ratio" mixes like this one - fueling equipment is much cheaper, and sealing concerns are lowered considerably.

This isn't a summer project I'm talking about getting involved in here. It's a Christmas break diversion which will consume perhaps three days of moderate effort and result in the completion of a system I've already done most of the work on. My summer project will be much louder, considerably more obnoxious, and likely capable of hurling .12g El Cheapo brand BBs through a good quarter inch of RHA equivalent :wink:
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Unread postAuthor: saefroch » Fri Oct 14, 2011 3:41 pm

I'm using 7.0.9, which was released in 2005 and I got this computer a few months ago so... Yeah. No idea where this issue is coming from. Here's a screenie:
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Unread postAuthor: DYI » Fri Oct 14, 2011 3:56 pm

Ah, I see you're not using one of the standard product sets. That's probably where the difference lies. I also note that you appear to have been playing around with GasEq for an extended period of time before taking that screenshot :wink:
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Unread postAuthor: Alster370 » Fri Oct 14, 2011 4:10 pm

Looks like this is just the motivation I needed to finish off that miniature 200X hybrid chamber...


Please do :D



I, unlike the OP, do not yet have a working electrolysis rig.

Its not actually working, just a mere stack of stainless steel, rubber and polycarbonate :D . But its a proper cell, so I have no doubt about it not working. It consists of 7 4x4" plates which when used in the dry cell configuration I have in mind, will give me ~half a litre a minute at around 20A. I should get it constructed in a few weeks. In the meantime, I will use one of my more ghetto electrolysis rigs as I aim to have a cartridge running this mix before the end of the month, at the latest.
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Unread postAuthor: Alster370 » Sat Oct 15, 2011 10:25 am

Sorry for the double post but, I've been thinking over hydrogen as a propellant and generally I came to the conclusion that for it to be in any way effective, It has to be at higher pressures.

the only problem is, hydrogen doesn't like being compressed with air or oxygen, and will at any given pressure point, auto ignite due to heating from compression. So I ask, would there be any reasonable practical way to reduce a hydrogen/oxygen mix's reactivity to compression?

My first thoughts were:

dissolve it into a liquid(that would also be combustible)?
Mix it with a gas to reduce its reactivity, but not affect its Combustion attributes (SOS,Temp,pressure etc)

Any thoughts? :?
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Unread postAuthor: jimmy101 » Sat Oct 15, 2011 10:40 am

Alster370 wrote:the only problem is, hydrogen doesn't like being compressed with air or oxygen, and will at any given pressure point, auto ignite due to heating from compression. So I ask, would there be any reasonable practical way to reduce a hydrogen/oxygen mix's sensitivity to compression?
Seems to me the easiest way is to simply compress the mixture slowly. Gases will transfer heat to the container walls very quickly and gases in general have pretty low heat capacities compared to most solids. So, a fast compression might heat up the gases by a couple hundred degrees, which is bad, but a slow compression will heat the container walls by just a couple degrees. How fast is "slow"? Compression over say 5 seconds should be slow enough. (1X combustion of propane in air in a closed chamber will spike at a couple thousand degrees but fall back to near ambient temperature within about 1 second, heat transfer from the hot gases to the container walls is very fast. http://www.inpharmix.com/jps/Chamber_Temperature.html)
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Unread postAuthor: Alster370 » Sat Oct 15, 2011 11:39 am

So how safe would you say compressing a hydrogen,oxygen mix using a bike pump or syringe was, given a slow compression? Also on the heat dissipation, one could add a heat sink style sheath to a bike pump and choose one made of aluminium, for maximum heat dissipation. Maybe I should give this a go. :?
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Unread postAuthor: saefroch » Sat Oct 15, 2011 1:54 pm

Wikipedia says the autoignition for the stoichiometric mix of hydrogen and oxygen is 570C or 1,065F. I think you'll be safe, but feel free to throw some numbers at it first.

DYI wrote:I also note that you appear to have been playing around with GasEq for an extended period of time before taking that screenshot :wink:
How do you figure that?
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Unread postAuthor: jimmy101 » Sat Oct 15, 2011 2:46 pm

Alster370 wrote:So how safe would you say compressing a hydrogen,oxygen mix using a bike pump or syringe was, given a slow compression? Also on the heat dissipation, one could add a heat sink style sheath to a bike pump and choose one made of aluminium, for maximum heat dissipation. Maybe I should give this a go. :?
The radiator would be a good idea. If the setup allows, you could just use a long (several feet) coil of small ID copper tubbing. The surface to volume ratio would be huge and I wouldn't think the gases would heat up appreciably with that much surface area to absorb heat.
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Unread postAuthor: mobile chernobyl » Sat Oct 15, 2011 3:20 pm

sounds like an intercooler! :)
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Unread postAuthor: Alster370 » Sat Oct 15, 2011 3:31 pm

sounds like an intercooler!
:D
Besides, Im not sure how one would make a pump which had a body of 7ft of coiled copper :) You could maybe use an air powered piston, but it seems like a lot more effort, none the less I will probably keep it in mind in case I dont have the balls to use a normal pump :D

I have more concern placed about the heat of the cartridge as I fill it, mostly because it will only be 1"x6" in size. :?
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Unread postAuthor: saefroch » Sat Oct 15, 2011 4:59 pm

You'd just pump the gases into the long thin copper piping, using a pump like the one I built.
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Unread postAuthor: ramses » Sat Oct 15, 2011 5:00 pm

I think you're fine. Even after firing my 10x hybrid, the (galvanized) chamber only gets slightly warm to the touch.
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