Propane:Oxygen air fuel ratio???

[billybob_81067]

Anyone here have a refrence website that gives an optimum air/fuel ratio for propane? I searched but came up with absolutely nothing. Actually I need a propane/oxygen ratio, but propane/air would also work since I can guesstimate that to be ~ 21% oxygen. I'm building a gopher/prairie dog blaster and I need to get the most violent burn for the greatest efficiency!

[MoeMag]

Is this going to be a potato launcher type thing or a torch?

Potato launcher...
I made a gun, than plotted the performance of different mixtures from a fixed shooting rig, until I found a maximum.
I did the time propane valve was open vs. shot distance (what ever goes the farthest had the most "umph" as long as other variables were held constant is what I figured)

Torch...
I have a gas forge that I run propane through a blower... just have an adjustable air mixture one of two ways, put a dimmer switch on the blower or put an adjustable choke in the air way. Also it seems to help to have an adjustable nozzle as well.

[billybob_81067]

It's a hole blaster thing that has a firing head on it and an igniter inside the head. Basically I have oxygen and propane running through torch regulators, and then going through valves. When you open the valves both the propane and oxygen run for the same amount of time and mix. Basically I just need to know what the optimum air/fuel or oxygen/fuel ratio for propane is so that I can get the most bang (literally!) for my buck. I will adjust the mixture by changing the output pressures on the regulators. I just want to get somewhere close by calculations before fine tuning it.

[rkjunior303]

[behemoth]

It's a hole blaster thing that has a firing head on it and an igniter inside the head. Basically I have oxygen and propane running through torch regulators, and then going through valves. When you open the valves both the propane and oxygen run for the same amount of time and mix. Basically I just need to know what the optimum air/fuel or oxygen/fuel ratio for propane is so that I can get the most bang (literally!) for my buck. I will adjust the mixture by changing the output pressures on the regulators. I just want to get somewhere close by calculations before fine tuning it.

Just fart in the hole, and drop a match in.

Why must you over engineer?

[mclaggan123]

well since O2 just supports combustion not actually burn then just the propaine should be fine. i assume your pumping propaine into the hole and then lighting it. try like an 80/20 mix but be very careful. let us know how it turns out.

[MANN]

Are you wanting it to burn, or to blow up?

[billybob_81067]

Are you wanting it to burn, or to blow up?

Blow up... and VIOLENTLY, so the shockwave kills some rodents!

I've got it rigged so I'm 25 feet away from the hole when I hit the igniter switch. I've seen one working before and it's pretty sweet.

[beam]

For what it's worth, I would think Tipmann would have some data on this. After all, they did develop a propane powered paintball marker.

Have you checked their forums to see if there are any technical/Tipmann people that would know?

[beam]

Found this on Wikipedia:

Propane undergoes combustion reactions in a similar fashion to other alkanes. In the presence of excess oxygen, propane burns to form water and carbon dioxide.

C3H8 + 5 O2 → 3 CO2 + 4 H2O
When not enough oxygen is present for complete combustion, propane burns to form water and carbon monoxide.

C3H8 + 3.5 O2 → 3 CO + 4 H2O


So that's saying 1:5 is too much propane to oxygen and 1:3.5 is too little.

Average them out for optimum would be the best place to start I guess.

[beam]

Just a note, that above equation is molecule ratio....I don't know how that would covert to volume.

[Tunaman]

Blow up... and VIOLENTLY, so the shockwave kills some rodents!

I've got it rigged so I'm 25 feet away from the hole when I hit the igniter switch. I've seen one working before and it's pretty sweet.

Make sure you are 25 ft from the TANK too! And the line! One of these barbecue tanks can kill 5 men at close range...be careful with propane please!

[dj89]

While we are talking about this, I wanna blow up a 20lb tank. I have a AR-15 and a road flare. What would be a safe distance?

[slade]

Just a note, that above equation is molecule ratio....I don't know how that would covert to volume.

someone didnt take highschool chemistry?

most gasses behave very similar to an "ideal gas"

[beam]

someone didnt take highschool chemistry?

most gasses behave very similar to an "ideal gas"

lol...yes took highschool chemistry...just a long long time ago.

I am the furthest from a chemist as can possibly be. I just hunted up the crap on wiki and spewed it out here. So if your looking to belittle someone about their mad chemiskills...you've got an easy target in me.