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Author: Subject: High-temperature flames.
The WiZard is In
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[*] posted on 7-4-2010 at 17:04
High-temperature flames.


This is "energetic" enough for me. I hope it doesn't annoy the moderator(s).

The late Herbert Ellern, Military and Civilian Pyrotechnics. 1968 sez — Chapter 27 High-Temperature Flames. Page 230

... cyanogen (CN)2 and carbon subnitride C2N2 ... furnish, with oxygen, flames measured at 4800 and 5300oK, respectively—higher than any other measured.

... since between 5500 and 6000oK one reaches "the limits of chemistry," [490] this means also that pyro hemically-created heat cannot raise above this limit.

John D Clark **
Igntion! An Informal History of Liquid Rocket, Propellants
Rutgers University Press. [I have misplaced the publication date.]

P. 36-7. The climax of unsaturation came with butyne di-nitrile, or dicyano-acetylene, N [triple bond] C [single bond] C [triple bond] C [single bond] C [triple bond] N which had no hydrogen atoms at all, but rejoiced inn the possession of three triple bonds. This was useless as as a propellant — it was unstable, but one thing, and its freezing point was too high — but it has one claim to fame. Burning with ozone in a laboratory experiment, Professor Grosse of Temple University [no citation] (who always liked living dangerously) attained a steady state temperature of some 6000 K, equal to that of the surface of the sun.

[490] B. Lewis, "High Temperatures : Flame," Sci. American, special issue on heat, 191, No. 3, p. 84 (Sept. 1954)

Anyone care to suggest an improved mixture?

** An eminently readable and interesting book. Used copies cost "HOW MUCH!" One would think it would be scanned and posted somewhere on La Net.

---------
But detonation traps [in the fuel line] aren't always the complete answer. We discovered that when, in the summer of 1960, we tried to fire a 10,000 pound Cavea B* motor. We didn't have Mike's trap at that time, so we inserted a battery of sixteen
0.25-inch loop traps in the line. Well, through a combination of this and that, the motor blew on startup. We never discovered whether of not traps worked - we couldn't find enough fragments to find out. The fragments from the injector just
short-circuited the traps, smashed into the tank, and set of the 200 pounds of propellant in that. (Each pound of propellant had more available energy than two pounds of TNT.) I never saw such a mess. The walls of the test cell - two feet of concrete - went out, and the roof came in. The motor itself - a heavy, workhorse job
of solid copper - went about 600 feet down range. And a six-foot square of armor plate sailed into the woods, cutting off a few trees at the root, smashing granite boulder, bouncing into the air and slicing off a few treetops, and finally, coming to rest some 1400 feet from where it started. The woods looked as though a stampeding herd of elephants had been through.

* 2-Methy - 1,4, diaza, 1,4 dimethyl, bicycle 2,2,2 octane dinitrate
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a_bab
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[*] posted on 7-4-2010 at 21:14


Another very hot flame I know would be from burning hydrogen in fluorine (with resulting HF fumes as a bonus). Ouch!
There are plenty of studies on the 'net concerning the H+F flame system.

But burning something in ozone, that's plain insane...

[Edited on 8-4-2010 by a_bab]
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[*] posted on 8-4-2010 at 00:22


H + F in optical resonator gives chemical Laser ... with high output !
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[*] posted on 8-4-2010 at 01:12


man Imagen the mirrors you would have to use for that ! :)

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hissingnoise
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[*] posted on 8-4-2010 at 03:25


Gah! Fuck Kelvin - why did he have to complicate things!
6000K is I believe, still 273*C short of the sun's surface!
But WiZard, you've obviously got up to some fun derring-dos in your time!
A stoichiometric mixture of airfloat charcoal or amorphous graphite in liquid O3 intitiated by a strong booster might on detonation produce a 'fairly' hot fireball.
Or spongy Al saturated with liquid O3?



[Edited on 8-4-2010 by hissingnoise]
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[*] posted on 8-4-2010 at 14:18


The below might be of interest. The file has been edited and some values added.

[Edited on 9-4-2010 by Formatik]

Attachment: high temperature chemistry.txt (6kB)
This file has been downloaded 428 times

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Mr. Wizard
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[*] posted on 8-4-2010 at 16:36


Nobody ever mentions the simple but technically difficult mono atomic H flame. This is the combination of mono atomic H combining to form diatomic H2.

It can be made, but not easily.
http://www.science.uva.nl/research/quant/sph.html

The energy available per mole is unmatched. Short of atomic reactions, it is the most energetic chemical combination by weight.
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[*] posted on 9-4-2010 at 03:26


Quote: Originally posted by hissingnoise  
Gah! Fuck Kelvin - why did he have to complicate things!
6000K is I believe, still 273*C short of the sun's surface!
But WiZard, you've obviously got up to some fun derring-dos in your time!
A stoichiometric mixture of airfloat charcoal or amorphous graphite in liquid O3 intitiated by a strong booster might on detonation produce a 'fairly' hot fireball.
Or spongy Al saturated with liquid O3?



[Edited on 8-4-2010 by hissingnoise]


If you want stuff to end up hot cooling it down to start with is not very helpful. Why use liquid O3 when you can use the gas and start a couple of hundred degrees hotter?
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[*] posted on 9-4-2010 at 03:39


Quote:
Why use liquid O3 when you can use the gas and start a couple of hundred degrees hotter?

Because the increased density more than makes up for the lowered temperature, obviously!



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[*] posted on 9-4-2010 at 07:50


In terms of the maximum reachable temperature, liquid of gaseous O3 won't change much. In liquid form it will "saturate" the reaction, thus maximizing the chances of getting the highest possible temperature from the combustion of something. The difference of a few hundreds degrees lower initially won't change too much the overall thermodynamics; I bet that if you manage to sink a hot coal in liquid O3 it will burn very well under "LOZ*" (actually the LOZ will likely explode).

We should never forget the old video featuring "how to light up a bbq with LOX", in which the coals are consumed in seconds, in a blazing hot hellish flame, melting everything in the path: now that's heat output!

As Mr. Wizzard said, the Langmuir's atomic hydrogen torch is no joke either: http://www.lateralscience.co.uk/AtomicH/atomicH.html

____________________________________
LOZ = Liquid OZone. Just made it up.


[Edited on 9-4-2010 by a_bab]
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[*] posted on 9-4-2010 at 10:37


Quote: Originally posted by a_bab  
Another very hot flame I know would be from burning hydrogen in fluorine (with resulting HF fumes as a bonus). Ouch!
There are plenty of studies on the 'net concerning the H+F flame system.

But burning something in ozone, that's plain insane...

[Edited on 8-4-2010 by a_bab]


Attachment: Explosives Detonation velocity table.doc (615kB)
This file has been downloaded 819 times


Google turned up this interesting XLS spread sheet

www.dcr.net/~stickmak/JOHT/propella.xls
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[*] posted on 9-4-2010 at 11:11


Liquid ozone explodes for no reason, so it has to be diluted with liquid air, N2, O2, etc. Even those are only partly suitable diluents, since they evaporate much easier leaving behind pure concentrated ozone, e.g. Gmelin mentions explosions easily occurring when O2 as a diluent evaporates.
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[*] posted on 9-4-2010 at 13:03


A higher temperature can also be achieved by pre-heating the reactants: So some Extra-1000 Kelvin are possible ...
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[*] posted on 10-4-2010 at 06:10


wow. that had never crossed my mind. so if you preheat air and propane (say to 800 degrees) the flame temprature go's up 800degrees acordingly ?

is there an upper limit to that ? so chould you use your preheated flame to preheat some more gas to get another 800degrees ?

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[*] posted on 10-4-2010 at 06:11


Quote: Originally posted by hissingnoise  
Quote:
Why use liquid O3 when you can use the gas and start a couple of hundred degrees hotter?

Because the increased density more than makes up for the lowered temperature, obviously!




Sorry, but it's not obvious to me that starting colder is a good way to end up hotter.
Also, since temperature is a matter of heat per molecule, rather than heat per gram, the density won't affect the final temperature.

It's already been pointed out that preheating the reactants will increase the final temperature so, as I say, it's far from obvious why cooling them would help.
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[*] posted on 10-4-2010 at 06:28


Well, it's pretty obvious to me that the difference in potential energy between liquid and gaseous O3 is great. . .

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[*] posted on 10-4-2010 at 08:18


Indeed, and the energy difference is that required to separate the ozone molecules (held together by dipole dipole interactions) and then to heat those molecules up to room temperature.
All of this energy is provided from the heat of reactions and so it's not there to raise the temperature of the reaction products. That's why, as far as I can see, the flame won't be as hot.
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[*] posted on 10-4-2010 at 08:53


Quote:
That's why, as far as I can see, the flame won't be as hot.

What I said was; 'a stoichiometric mixture of charcoal in liquid ozone'.
It will, on detonation, produce a much hotter flame than any oxidation by gaseous ozone. . .
That really should be obvious to anyone!



[Edited on 10-4-2010 by hissingnoise]
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[*] posted on 10-4-2010 at 11:18


No.
A stoichiometric mix of gaseous ozone and charcoal will release more heat (because it doesn't have to waste energy boiling the ozone) and it will start off hotter so it will end up much hotter.
Admittedly it would be tricky to disperse the charcoal evenly through the gas but that's just a technicallity.

What should be obvious to anybody is that cooling stuff down doesn't make it hotter.

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[*] posted on 10-4-2010 at 11:26


Quote: Originally posted by hissingnoise  
What I said was; 'a stoichiometric mixture of charcoal in liquid ozone'. It will, on detonation, produce a much hotter flame than any oxidation by gaseous ozone. . .
That really should be obvious to anyone!
It's not obvious to me. Enthalpy density is what you are seeking to optimize, but it's not obvious that always translates into high temperature. The outward-directed kinetic energy released by detonation isn't regarded as "high temperature" but rather "high velocity". So you have two kinetic energy terms, one microscopic for temperature and the other macroscopic for velocity. Since energy is conserved, you have to make the argument that the partition between these two energy modes gives you the high temperature you're claiming.
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[*] posted on 10-4-2010 at 11:36


Noobody said that fact of having a cold oxidizer will result in a hotter flame. It's the fact that if you start with concentrated reactants, the results are better. And it happends that in order to get liquid ozone, oxygen whatever you need to such energy from the molecules, energy that will be paid back at the reaction time. A simple thermodynamics calculation will reveal the amounts for those who are curious.

It's like comparing a butane flame in air: it's better tu use pure oxygen instead. The resulted flame melts steel and such.

In an ideal world, if you can supply a continous stream of ozone over your "porous Al" the resulted temperature will be higher then using oxygen (ozone already has more energy in the molecule and it's more chemical active). Also, if the ozone will be streamed at 1000 degrees C, the reaction will become explosive due to the speed, and the surplus of energy.

Neither of these are practical in our world, so why fighting?
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[*] posted on 10-4-2010 at 11:51


It's not a "fight" it's a request for scientific information.
Specifically, I want to know why starting with something colder, and then making it do more work will give a hotter flame.
Incidentally, while nobody said that "having a cold oxidizer will result in a hotter flame", hissingnoise has repeatedly said that liquid ozone will give a hotter flame than the gas would.
Unless you plan to liquefy the ozone by compression alone then it's bound to be colder. (Some brave soul has measured the critical point and it's 12 degrees below freezing. You can't get liquid ozone unless it's cold)

The point is that, even if I'm wrong, saying "That really should be obvious to anyone! " without offering any sort of explanation is unhelpful.

Incidentally, the reason a butane flame is hotter in oxygen than in air is because it doesn't have to waste energy heating up nitrogen. Nobody is proposing to add a diluent here so that's a red herring.



[Edited on 10-4-10 by unionised]
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[*] posted on 10-4-2010 at 14:48


Quote:
It's not a "fight" it's a request for scientific information.

What we have is a simple difference of opinion.
But I still maintain that the detonation of liquid ozone/fuel will be more energetic than that of ozone gas/fuel.
Ozone is liquid at -120*C, but as I said already, the density-difference should more than make up for the low temperature.



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[*] posted on 10-4-2010 at 16:45


I don't think it will be more energetic, but more exothermic. An example is given in the chart above comparing LOX/C2N2 detonation against combustion of C2N2 in oxygen.
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[*] posted on 11-4-2010 at 01:22


Hissingnoise,
I don't see why the volume that the reactants occupy makes a difference to the energy released, and you have made absolutely no attempt to explain why it might do so.

The temperature is a measure of the energy per molecule, it doesn't depend on the volume.
If you have the same reaction i.e. 3 C +2 O3 ---> 3 CO2 then the energy released is the same per molecule more or less independently of the volume or initial temperature so the rise in temperature will be the same.

However if some of that energy is used converting the liquid to a vapour then there will be less left over.
Also it will have started colder so all things being equal it will end up colder.

As I have said there's a phase change that takes place when the ozone boils and you need energy to do that. Where do you think that energy comes from if not from the heat of the reaction?
If that heat goes into boiling the ozone why do you not think this will reduce the final temperature?

You keep restating that you believe it will get hotter if it starts colder, but you don't provide any explanation at all. To make this into a scientific discussion you need to explain your opinion rather than repeating it.

If I'm wrong then fair enough, but don't just say I'm wrong; say why.
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