Predicting Pressure of an Explosion
Predicting Pressure of an Explosion
(OP)
I'm having trouble finding an equation(s) that will help me predict the maximum pressure inside an enclosure due to an explosion. Although air and vapors can get into the enclosure, I will assume a constant volume. I've thumbed through some old thermo books but nothing jumps out at me. Does such an equation(s) exist? If so, what is it or where can I find it? Thanks.





RE: Predicting Pressure of an Explosion
Wouldn't the maximum pressure inside an enclosure prior to explosion be the maximum pressure capability of the enclosure itself? After explosion, there is nothing to hold the pressure in the enclsoure.
Are you looking for the "force" generated by the explosion?
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RE: Predicting Pressure of an Explosion
I presume you have a situation where you have a vessel with a potentially explosive environment inside it. You've been asked to determine what happens if it goes boom and presumably the vessel will be designed to withstand/contain that. I dealt with that a loooong time ago with a food product processing plant. If I recall correctly, there was an article or two, maybe even a standard, which dealt with "deflagration." Never knew the word existed, basically the difference between "combustion", "deflagration", and "explosion" is the speed of the wavefront when the stuff oxidizes. I'll poke around a bit and see if I can find the old articles; in the mean time try google'ing on "deflagration" and see what you get...
Or... on a similar note, are you designing containment for testing explosive devices?
jt
RE: Predicting Pressure of an Explosion
Refer to the Chapman-Jouget curve. This basically represents state conditions for the resulting mixture with the added heat from the combustion. The plot is pressure vs. sp. volume. From the initial conditions of p1, v1, a line is drawn which is tanget to the p2, v2 final condition curve. Two tangents may be drawn. One is results in a pressure rise - a detonation, and the other a pressure drop--deflagration.
Good luck
RE: Predicting Pressure of an Explosion
RE: Predicting Pressure of an Explosion
RE: Predicting Pressure of an Explosion
RE: Predicting Pressure of an Explosion
Look at this site for some definitions.
http://
Geoffrey D Stone FIMechE C.Eng;FIEust CP Eng
www.waterhammer.bigblog.com.au
RE: Predicting Pressure of an Explosion
My explantion of shock and detonation were oversimplified.
From a search of your recommended website, I did glean the following which might also be of interest ot others.
Regards
The ideal detonation speed, known as the Chapman-Jouguet velocity, is a function of the reactant composition, initial temperature and pressure.
Chapman-Jouguet Velocity This is the velocity that an ideal detonation travels at as determined by the Chapman-Jouguet (CJ) condition: the burned gas at the end of the reaction zone travel at sound speed relative to the detonation wave front. CJ velocities can be computed numerically by solving for thermodynamic equilibrium and satisfying mass, momentum, and energy conservation for a steadily-propagating wave terminating in a sonic point. CJ velocities in typical fuel-air mixtures are between 1400 and 1800 m/s
Sonic point The point at which the flow velocity is equal to the speed of sound. When this is applied to detonations, the velocity is computed relative to leading shock front. The elementary Chapman- Jouguet condition is that the sonic point occurs at the end of the reaction zone when the products are in equilibrium.
RE: Predicting Pressure of an Explosion
genb