Explosion pressures

[jade]

I am looking for some good reference material for calculating explosion forces of a gas, i.e. hydrogen. Obviously pressure will be a function of the containment vessel size,which can be calc'd with a known force. For a given mass of explosive material, is there a formula to calculate force after ignition.

 

[IRstuff]

You might want to try and post this in the Ignition, Combustion and Detonation Engineering or Demolition Engineering forums.

I, personally, don't think that simply mass is sufficient to determine blast pressure. One key parameter is burn rate of the material. The same quantity of diesel and gasoline have radically different combustion behavior.

TTFN

 

[nbucska]

I don't think it is so simple: e.g. 2:1 mixture of H2 and O2
explodes with a click-like sound in an open cup but gives
a painfully loud explosion if the cup is closed with a
soap bubble. <nbucska@pcperipherals.com>

 

[ardilesd]

To make some previous estimation you nedd, at least,
- a model of the reactions involved
- the heat of combustion and thermodinamical model
- some model of the gas phase behaviour.
In the simplest case :

H2 + 1/2 O2 --> H2O

From the mass balance you see that there is a decrease in volumen (from 1 1/2 to 1 ), so the reaction would lead to a decrease of pressure if there is no heat involved !!

But, with the heat balance , you know that there is an important increase in temperature (due to combustion) an then, in adiabatic conditions, you can calculate the adiabatic temperature.

Finally, with a model of gas phase, the simplest would be ideal gas: P = n . R. T / V, you can estimate the final pressure.
Hope this helps a little

 

[vpl]

I think you also need to take into account the heat of combustion: consult a good chemical or mechanical engineering handbook. Patricia Lougheed

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Forums&quot;

 

[jade]

Thanks all. I do realize to get an exact answer will require an iterative testing process. I was interested in a back of the envelope approach to see if my design is in the ballpark.

 

[IRstuff]

There are also some sizable physical dependencies, e.g., how the fuel and oxider are physically distributed. The classic cases are diesel and aluminum.

Diesel in liquid form is quite tame, but in vapor form with plenty of oxygen, it will combust reasonably well.

Aluminum under most conditions will simply burn, but aluminum powder dispersed with plenty of oxygen as in an FAE, will produce spectacular effects.

TTFN

 

[saxon]

jade, There are three combustion states that can occur, Conflagrations, Deflagrations, and Detonations. As to which state is occuring is dependant on the &quot;UEL/LEL&quot; limits, ignition energy source levels, oxidizer type and levels, containment vessel type, and a host of other variables. FIKE Corp. are experts in this field and may have something right up your alley. Also, check the web for the various combustion states, this will give you a start point.

Goodluck!
saxon

 

[mgp]

Perhaps you might find this thread interesting

thread794-26767