From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: alt.engr.explosives
Subject: Re: temp of ANFO explosion?
Date: 18 Jan 1996 20:13:57 GMT

In article <4dlq8s$gbo@norm.uoknor.edu>, major@rodent.ecn.uoknor.edu
(Dan Major) says:

>Does anyone know the aprox. temp. generated by ANFO types of
>explosions? I realize that there are several different hydrocarbon
>fuels that can be mixed with AN - I just grouped them all together as
>"fuel oil". Curious just how much thermal effects would be noticed from
>AN-hydrozine, AN-nitromethane, AN-FO,etc. Thanks.

The thermal effects are minor for these mixtures. None of them
produce much flash even as observed at night. The hydrazine
based compositions are particularly dark because the products
are all gases. I once calculated the explosion temperature of
a somewhat water-diluted Astrolite formulation at less than
about 1500 degC, cool enough to fire in large quantities in
very dry brush and lumbering slash. When we needed hot 
formulations to add ignition capability to an explosion we
added lots of aluminum to get the calculated temperature
up to 3000-4000 degC.

Detonation temperatures are much higher than explosion 
temperatures where the latter refers to the expanded product 
cloud. There has been a lot of speculation and disagreement
about the values of detonation temperatures.

Jerry (Ico) 

From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: alt.engr.explosives
Subject: Re: temp of ANFO explosion?
Date: 20 Jan 1996 03:09:16 GMT

In article <4doagg$a1@norm.uoknor.edu>, major@rodent.ecn.uoknor.edu
(Dan Major) says:

>Thanks for the reply! 
>Wow! less than 2000 degrees F - that's cooler than a propane torch, much
>cooler than an oxy-acetelene torch! I've measured the temperature of the
>flame off of a Bic lighter at about 1300 F - same ballpark.

Take all information re the temperature of flames and 
explosions with a grain of salt. Many referenced are 
incorrect because of experimental inaccuracies. For 
instance, the maximum flame temperature butane/air 
should measure above 2000 degC or 3600 degF. 

Chemical explosions and flames have a lot in common
because the heat released in well balanced stoichiometric 
reactions is the same whether the reaction is by flame or 
by detonation. Many compositions can react both ways. Are 
the temperatues then the same? Ahem, it depends. At 
constant volume in a perfectly insulated shock-proof container 
(hard to do), Yes. In free air, well, it depends. Energy can 
be lost to radiation, conduction (vastly different for flames 
and explosions), diffusion (flames only) and shock energy 
(explosions only). Still, in general, as long as we limit 
"explosives" to the fuel/oxidizer kind (no soda pop cans),
explosions and flames will still play in the same temperature 
ballpark, but it is a large park.

One might keep in mind that when low temperatures are quoted
for modified explosives such as salted dynamite, the quoted 
 average explosion temperature of the expanded gas cloud is 
just that, an average. That temperature takes into account 
the loss of heat to the salt, which may take a fraction of a 
second to reach near thermal equilibrium.

Also note that the expanded cloud is a darn sight cooler than
the material as it detonates. There have been estimates of
detonation temperatures up to 6,000 degK for nitroglycerine,
based on radiation measurements in transparent probes.

Jerry (Ico)

From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: alt.engr.explosives
Subject: Re: temp of ANFO explosion?
Date: 20 Jan 1996 20:48:40 GMT

In article <4doqic$n99@ixnews7.ix.netcom.com>, silent1@ix.netcom.com (The
Silent Observer) says:

>>Wow! less than 2000 degrees F - that's cooler than a propane torch, much
>>cooler than an oxy-acetelene torch! I've measured the temperature of the
>>flame off of a Bic lighter at about 1300 F - same ballpark.
>
>Argh -- that's the problem with older American scientific literature -- 
>you're never certain whether it's metric (Celsius) or English 
>(Farenheit).  We should probably calibrate this against the ignition 
>temp of a mixture of 9% methane in air -- which was quoted as igniting 
>between 600 and 700, a range that would not overlap between F and C 
>scales.  My CRC is still packed, does anyone else have that ignition 
>temperature?
>
>I'm inclined, on further thought, to suspect that would be C scale; I'm 
>familiar with a bright-red-hot wire igniting hydrocarbon vapors (like 
>the igniters in kerosene heaters), but 600F wouldn't be even close to 
>red heat (which starts close to 1000F).

Silent, I'm having trouble following this thread. Are you talking 
about minimum ignition temperatures or combustion temperatures?

Autoignition temperatures for the aliphatic hydrocarbons lie 
roughly in the 200-540 degC range with the higher values 
corresponding to the shorter chains, terminating in methane.
The lower end of this range is approached by hydrocarbons
having 8-10 carbon atoms.

Single values for autoignition temperatures are an 
oversimplification as the actual temperatures vary with the
surface of any confining vessel, heating rate, trace 
impurities and the pressure. Most low temperature ignitions
may be viewed as leading to cool primary flame regimes which
may pass through a mixture producing intermediate incomplete
combustion products or shift to complete secondary combustion.
The cool flames are more prevelant in the higher hydrocarbons,
and their temperatures are closer to the autoignition
temperatures.

Jerry (Ico)

Stoichiometric full combustion produces very much higher
temperatures than the minimum ignition temperatures. Methane,
for instance approaches a combustion temperature in air of 
1800 degC and the longer hydrocarbons produce significantly
higher temperarures. 

From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: alt.engr.explosives
Subject: Re: temp of ANFO explosio
Date: 24 Jan 1996 02:01:47 GMT

In article <4e3vsc$7sk@news1.sunbelt.net>, pgennrich@sunbelt.net says:

>> Davis also
>>  mentions that Hg(ONC)2 cannot ignite BP due to the short "burning" time
>>  of the fulminate, although the explosion temperature is well above
>>  that required for BP.
>
>
>Historical information time, please.
>
>I'd been under the assumption that the early self-contained 
>cartridges for pistols and rifles used fulminate as a primer.  
>Obviously, there were BP carts before smokeless became more 
>available, so what WAS the priming compound used in early 
>pistol/rifle cartriges?

My copy of Davis wandered away a long time ago, but if the 
attribution to Davis is correct, then it is undoubtedly
taken out of context. Mercury fulminate is more than adequate
to ignite BP in the geometry of a cartridge. The fulminate
may detonate rapidly, but this does not mean that its 
reaction products carry less heat or cool off any faster 
than those of an energetically comparable low explosive.

A fully expanded explosion cloud of reaction products may
not have enough local volumetric heat capacity to raise other 
materials to the ignition temperature, but the spew of a hot 
gas jet, as from a primer is another thing entirely.

Jerry (Ico)

From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: rec.pyrotechnics,alt.art.pyrotechnics
Subject: Re: If you are a fire expert please read.
Date: 20 Jul 1996 23:26:39 GMT

In article <4so5pt$b7h@underworld.centrum.dk>, Peter Selmer Gade
<selmer@centrum.dk> says:

>Get some heat resistant piece of some sort, and heat it till it has the 
>same temp, as you torch. Then Quickly dump it in some water and measure the 
>rise in the temp of the water. With some non-complex equations you can 
>calculate the exact temp of the torch... You can find the procedure 
>described in any 1. year physics book! If you cant find the procedure, 
>E-Mail me and i will send the complete procedure!

Nope. It won't work.  Typical hydrocarbon flames reach about 2100 K, but
they are incapable of heating an object to that temperature unless 
the mass of burning gases is great enough to compensate for radiation
from the solid or unless the solid is too small (has too little 
radiating surface) to be of any use in measurably warming a typical
calorimeter setup.

As an example, it is difficult to melt copper much more massive than 
fine wire (M.P. ca. 1080 C) with a propane torch having a maximum
temperature around 1830 C.

Jerry (Ico)