new type of fuel

Boom! The classic potato gun harnesses the combustion of flammable vapor. Show us your combustion spud gun and discuss fuels, ratios, safety, ignition systems, tools, and more.
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mike1010
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Fri Jun 29, 2007 12:49 pm

what do you think i i used my airbrush to vaporize particles from say gasoline or some sort of alcohol then spray it in would it have a better effect that regular butane from deodorant?
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hi
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Fri Jun 29, 2007 12:58 pm

i dont think gas is smart because it will probably settle and will burn rather than ignite.

alcohol might work, but im not sure.
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mike1010
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Fri Jun 29, 2007 12:59 pm

ok ill give it a try
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jimmy101
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Fri Jun 29, 2007 1:32 pm

You can use liquid fuels but they will not out perform propane or butane.

Even though the energy content is about the same for liquid fuels, the difficulty in measuring the very small volumes, along with the problem of getting it to evaporate completely, usually means that liquid fuels don't work as well as gaseous fuels. A chamber fan is even more important with liquid fuels than it is with gases.

For a 100in<sup>3</sup> chamber it takes about 2 drops of gasoline for a stoichiometric mixture.

Edited for Engrish.
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TechnoMancer
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Mon Jul 02, 2007 2:58 pm

could you not use an injector from a diesel engine to atomize the fuel so that it will burn more completely???
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jimmy101
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Tue Jul 03, 2007 3:25 pm

A automotive fuel injector really won't help all that much, especially once you take into account the need for the injecctor, injector controller and high pressure pump for the liquid fuel...

It would be cool but one hell of a lot of work and $$$ for a system that won't perform any better than a traditional propane meter.
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paaiyan
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Tue Jul 03, 2007 3:27 pm

alcohol would vaporise better. It's more volatile than gasoline so given a few seconds after injection it would probably be in the gas phase. The problem with that is, most alcohols are diluted with water or something else.
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sandman
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Tue Jul 03, 2007 5:30 pm

well you can always distill the alcohol
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666lucky693
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Tue Jul 03, 2007 10:33 pm

u could use the dry gas isopropyl its sold for gas to make it better that would work
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jimmy101
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Wed Jul 04, 2007 11:35 am

sandman wrote:well you can always distill the alcohol
Distillation will only reduce the amount of water in ethanol down to about 5%. To get drier than that you need to use a chemical drying agent.

The 5~30% water in many kinds of alcohol (methanol, ethanol and isopropanol for example) really won't affect the perfrmance of the gun all that much. You do need to take into account the presence of the water when deciding how much fuel to use.
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psycix
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Wed Jul 04, 2007 3:48 pm

gas > liquid vapor

Vapor will settle, stick and do other nasty things.
Using a gas like propane works good enough.
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