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Mechanics of combustion.


Guest Mark_the_pyro

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Guest Mark_the_pyro

Whoo! First newb post! Ok, anyways, this thread should be for explaning what you will need for a combustion to take place, such as fuels, oxidizers, etc....

Someone tried to explain this to me today, but it still doesn't make that much sense. So maybe this thread might help out some of the newer member too. Thanks.

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Have you ever touched a chemistry book? What, are you in the 5th grade? I learned this in 7th grade. A fuel is a substacnce that is burned by the process of oxidation. Oxidation is where atoms from the molecule of the fuel combine with oxygen atoms to form a new compound. An oxidizer is a chemical that adds oxygen molecules to the system (KNO3, KClo4, etc.) .
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Guest Mark_the_pyro
Thank you teknix. And to you dragonman, I think it is a legitimate question to ask, as I really was not sure, and this is being posted in the newb section. Lighten up, not everyone knows everything about pyrotechnics when starting.
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Search much?

 

Few basic points that will clear some stuff up:

 

1)It doesn't quite have to be oxidation in the sence that oxygen is used to oxidise

2)Electrons drive all reactions

3)Entropy increases

4)Energy is released due to bond breaks/formations

5)Look up redox

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Well yea I know that there doesn't necessarily have to be oxygen atoms present, just transfer of electrons. But I was trying to describe a basic combustion scenario. My apologies for not going further into it. When looking up redox remember G.E.R = Gain Electrons Reduction and L.E.O. Lose Electrons Oxidation.

 

If you are asking for mechanincs as in why a firecracker blows up. Then it is like this. An exothermic reaction causes mass amounts of gas to be produced which are more than the case can handle so the case ruptures. The other way is that a very hot exothermic reaction causes an air pocket to expand and create enough pressure to rupture the case.

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I prefer OIL RIG, Ox is loss (of e-) and Re is gain (of e-)

 

Zn + s ==> ZnS is redox reaction because of the change Ox state, even though it has no O molecules in it.

 

Remember REDOX RXN is a change in Ox state.

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"... causes an air pocket to expand "

 

Speaking of flash I guess. Since it produces only Al2O3 and KCl, both solids, people invented the 'exploding air pocket' to explain the bang. The fact that loose-filled tubes are louder than stuffed ones seems to support this.

 

Reality is different. Just think: Air going from 300K to 4500K will create about 15 bar, or 210 PSI. This will hardly burst a weak paper tube, it's twice your water main. Considering flash bursts steel pipes, we need a different mechanism....

 

Ever thought that KCl can vapourize? Plus, at those temps equilibrium favours Al2O, which are also gases (and forms Al2O3 on cooling).

The reason for loosely filled tubes being louder is the faster flame propagation between the particles = faster pressure rise.

 

Now someone please explain how air can oxidize ions in solution, like Fe2+ --> Fe3+ ? If it enters the liquid and becomes OH-, leaving Fe3+, there must be a molecule of water involved. This leaves one H, NOT H+ (H3O+). But it won't bubble!

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I would like to add... This is the newbie section so I really disapprove with flaming or rude comments.. Don't even think about posting rude comments in the newbie section!
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Eh hem, and who put you in charge? You've been acting rather pretentious lately. I suggest you knock it off. You can't tell member what they can or can't do, or what do you or don't want to hear. If you have a problem you can contact an admin. You have to realise that no one cares what you have to say or think, as you are just an unknown newbie to a fair portion of the population.
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Hmmmmm... Do you think it's fun to flame in THE NEWBIE SECTION? If so.. That's cool you can run your forum that way, I don't care.

 

As of me being a newbie to a majority or the population.. You have maybe 120 members on this forum and maybe 70+ know me from other forums or Totse.

 

I wasn't really telling anyone what to do but I find it pathetic that people have to flame in a newbie Q thread.. :rolleyes:

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No one was flamed. One person was being pissy and half-told him off, the rest of us provided help. If you want a flame I'm sure some people would be happy to dish one out to you.
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I'm sure I could get a few... Because half of all the forums have those fuckers who do absolutely nothing but flame.. Looks like 30-06 learned flaming isn't the way to get kewls to leave.
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I'm sure you'd get a flame not beca use people like to flame but because your a dickhead.

And to those 70+ people that know you I am sure `65+ think your a wanker.

 

Someone had to say it.

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Forget what I wrote before, I'll be the man and just stop arguing because it's completely useless... Edited by kwstag
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