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hybrid fueling

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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hybrid fueling

Unread postAuthor: pat123 » Sat Mar 08, 2008 9:28 am

I know that you use 4.2% propane and the rest air. when you go to 2x do you use 8.4% and so on?

how much pressure of each would you use. there would be a difference in using .42 psi of propane and 9.58 psi of air and using 4.2 psi of propane and 95.8 psi of air. or would you use 14.7 psi for 1x and 29.4 for 2x and so on.

thanks
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Unread postAuthor: DYI » Sat Mar 08, 2008 10:03 am

Firstly, you have no idea what you're doing, so I advise you do some research before you waste your money.

A 1x mix (regular combustion), in a completely airtight chamber, uses 14.7 psi air (atmospheric pressure), and about 0.644 psi propane. If the chamber isn't airtight (which is impossible for a hybrid), then it uses about 0.617psi of propane, because some air is displaced from the chamber.

You really should be able to figure it out from there if you're going to build a hybrid.
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Unread postAuthor: pat123 » Sat Mar 08, 2008 10:30 am

Ok thanks,
so when I go to 2X I double the pressure of both right?
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Re: hybrid fueling

Unread postAuthor: psycix » Sat Mar 08, 2008 11:39 am

pat123 wrote:I know that you use 4.2% propane and the rest air. when you go to 2x do you use 8.4% and so on?

how much pressure of each would you use. there would be a difference in using .42 psi of propane and 9.58 psi of air and using 4.2 psi of propane and 95.8 psi of air. or would you use 14.7 psi for 1x and 29.4 for 2x and so on.

thanks


Well, in the end its still 4.2% no matter what mix

Just inject the normal amount of fuel (4.2%) twice, or more times and then pressurize it up further to your amount of mix with air.

If you inject one shot of propane for 4,2%, then inject air until there is atmospheric pressure inside, wich is probably in there already (unless you suck the chamber vacuum)
If you inject 2 shots of propane then inject air until you got 14,7psi (1 bar) in it.
If you inject 3 shots of propane then inject air until you got 2 bar in it.
And so on.
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Unread postAuthor: shiftyguy » Mon Mar 17, 2008 2:14 pm

This is a handy page to sort out how many PSI/Bar

http://www.ilpi.com/msds/ref/pressureunits.html
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Unread postAuthor: SpudFarm » Mon Mar 17, 2008 2:19 pm

or you can just go to google and search "2psi in bar" and so on...
you can also "50 pounds in gram"
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Unread postAuthor: DYI » Mon Mar 17, 2008 6:12 pm

My original answer may not be right, as I'm not even sure that I understand the topic now - Spudblaster still has me confused, and I'm inclined to believe that he's right.
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Unread postAuthor: pat123 » Mon Mar 17, 2008 6:29 pm

so if I use one bar i use 4.2% of that and if I use 6 bar use 4.2% of that also right?
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Unread postAuthor: DYI » Mon Mar 17, 2008 6:38 pm

so if I use one bar i use 4.2% of that and if I use 6 bar use 4.2% of that also right?


Take the total volume of gases in your chamber (converted to atmospheric pressure). Propane should comprise 4.2% of that. This is the end result that you want if you intend on it firing.
I suggest contacting SB15 for some rather mind-boggling advice on how to achieve this end result :roll:
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