10 replies to this topic

[exat808]

I am looking for some verifiable figures for the energy output of Flash Powder. I appreciate that there are many variants of the substance but what I am looking for is something along the lines of -


Composition make-up (% of fuel / %oxidiser )

Energy output per specified weight - for example x joules per gram

Mean temperature of the measurement

Source of the data



Thanks in advance.

[fruitfulsteve]

Complicated stuff Perhaps a certain speaker at the AGM might be able to help, or may even be able to test some as part of a demo or something.

[exat808]

Complicated stuff Perhaps a certain speaker at the AGM might be able to help, or may even be able to test some as part of a demo or something.

Thanks. I'll stick to text books.

[whoof]

This may be worth a look , probably have to pay for the full article to find out though.
http://resources.met...6k&size=largest

[BrightStar]

Yep, it's a tricky one...

As someone who is decidedly not qualified to answer I'll give it a stab anyway.

Our starting point might be to assume a roughly stoichiometric mixture - say 64/36. The difference between the enthalpy of formation of our starting mixture compared with that of the reaction products should give some idea of the energy released per gram. This could be measured in the lab with a sealed underwater combustion chamber (bomb-calorimeter). The result however will be somewhat misleading as the reaction products from flash are essentially solids. The 'bang' seems to come from the vaporised particles and moisture that expand and promptly re-condense. We therefore have to think about the useful (coupled) energy released which, unlike conventional explosives is probably rather different.

As for reaction pressure and temperature, I guess we're back the good old PV=nkt regime from the physics classroom... Confine the volume, the pressure escalates, confine both and the temperature increases proportionally. Given that the stuff does self-confine we tend to get a bang. The temperature could be estimated via colour spectrometry to a reasonable degree but it's white hot, so pushing at least 4000 Kelvin.

If it does actually detonate of course (still hotly debated... technically I suspect not), then we're in to a different regime altogether...

Edited by BrightStar, 13 March 2012 - 08:28 PM.

[exat808]

Thank you for the responses so far. I was ( naively) hoping that there would be a text book equation to work through on the basis of some known constants such as temperature and mix of constituents. I have similar equations in text books from my military days for NC and NG compositions but nothing for flash comps. The figure is needed as a comparison for some development work on another project.

[whoof]

Sometime back there was a net discussion comparing an M80 to a stick of something.
I never saw a convincing answer, theories were anything from 4 to 1 to 20 to 1.

I had a good look and the above abstract was all i found.

Plenty of accidents in early photographic days but no real science, mostly Mg though.

Quote

" [14,15], but to the best of our knowlege nothing has been published
on the thermal behavior of AL+ Potassium chlorate."

It is possible that no-one has done the science you need.

I did wonder if power rather than energy would be a better measure as it takes into account detonation speed.

Best answer i saw was b**w something up and compare the size of the bits afterwards, well it made me chuckle anyway.

[Pyromancer]

It might be worth consulting the Journal of Pyrotechnics, this information will probably be in one of the issues or their dirctionary of pyrotechnics publications.

These are American publication packed full of technical pyro content - well worth getting, they used to be put together by Ken and Bonnie Kosanke (highly regarded pyro chemists).


I know some Americans that run speed trials with flash compositions:

A long tray filled with composition with two pieces of fishing line spaced at 1 metre holding down micro switches, these trigger and stop a timer as each piece of fishing line is burned though. Apparently the fastest compositions are approaching detonation velocities!

Hope this helps.



Steve

[exat808]

It might be worth consulting the Journal of Pyrotechnics, this information will probably be in one of the issues or their dirctionary of pyrotechnics publications.

These are American publication packed full of technical pyro content - well worth getting, they used to be put together by Ken and Bonnie Kosanke (highly regarded pyro chemists).


I know some Americans that run speed trials with flash compositions:

A long tray filled with composition with two pieces of fishing line spaced at 1 metre holding down micro switches, these trigger and stop a timer as each piece of fishing line is burned though. Apparently the fastest compositions are approaching detonation velocities!

Hope this helps.



Steve

Thanks Steve.
I think that my dilemma has been resolved thanks to some data extracts supplied by Helix.
Thanks to all who responded.

[pyrotrev]

Danny: IIRC, there were some studies done on the TNT equivalence of flash - I think it was in the Journal Of Pyrotechnics, though there's a figure listed on the NCTC site.

[exat808]

Danny: IIRC, there were some studies done on the TNT equivalence of flash - I think it was in the Journal Of Pyrotechnics, though there's a figure listed on the NCTC site.

Thanks Trevor.