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Will this work for 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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Will this work for fueling.

Unread postAuthor: 8tonsemi » Mon Jun 04, 2012 9:12 am

I was thinking this morning and this new type of metering came to mind that I haven't personally read before. I goes like this. you use a 96:4 ratio of fuel and for the mixes it goes like this. 10x mix = 96psi of air and 4psi of fuel. So it's going to use a standard way of fueling so 1x mix would equal 9.6 psi of air and .4 psi of fuel. Does this way make sense and is it safe?
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Unread postAuthor: boyce123 » Mon Jun 04, 2012 4:13 pm

if you look at the gas law (PV=nRT), it may be easier to understand why this method is slightly flawed. Though its in an ideal situation, the gas law implies an inverse relationship between pressure and the number of moles of gas (P1/n1=P2/n2, if all other variables are kept constant), thus as the pressure increases, the inverse relationship must be compensated for with the difference in pressure. So your question is if its possible to generate a 'standard' fueling dierectory, the answer is yes in an idealized situation, though the real world is not ideal, so we must rely on empirical data for more accurate assumptions.
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Unread postAuthor: Fnord » Mon Jun 04, 2012 6:13 pm

Haven't we been over this before?

You're also going to need to compensate for the air that's already in the chamber.

http://www.spudfiles.com/forums/hybrid- ... 13602.html
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Unread postAuthor: DYI » Thu Jun 07, 2012 12:52 pm

What you describe is manometric metering. Ignore boyce's comment, it is nonsense. By the ideal gas law, what you propose is exactly correct.

It isn't, of course, because gases are not ideal. However, you'll need to run uncommonly high mixes before non-ideal gas effect become more prominent than measurement inaccuracy in fueling and the error caused by lack of instant mixing during fueling.
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Unread postAuthor: boyce123 » Thu Jun 07, 2012 9:43 pm

sorry for that, i realized that my logic was reversed after i posted the comment...
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