Explosion, critical condition

A natural ex-plosion is also an uncontrolled and unexpected event. However, unlike an accidental c.xplosion it cannot be prevented. Some e.xamples of natural explosions include lightning and olcanic eniptions. Under the right critical conditions natural e.xplosions also trigger and cause accidental explosions. 

Adler, J. and Enig, J.W., 1964, The Critical Conditions in Thermal Explosion Theory with Reactant Consumption, Combustion and Flame 8, 97. 

The monomer is sensitive to light, and even when inhibited (with aqueous ammonia) it will polymerise exothermally at above 200° C [1]. It must never be stored uninhibited, or adjacent to acids or bases [2], Polymerisation of the monomer in a sealed tube in an oil bath at 110° C led to a violent explosion. It was calculated that the critical condition for runaway thermal explosion was exceeded by a factor of 15 [3]. Runaway polymerisation in a distillation column led to an explosion and fire [4], See other polymerisation incidents... 

If the initial pressure is increased to some value P2, the heat release curve shifts to higher values, which are proportional to P" (or p"). The assumption is made that h is not affected by this pressure increase. The value of P2 is selected so that the ql becomes tangent to the qr curve at some point c. If the value of h is lowered, qr is everywhere greater than ql and all initial temperatures give explosive conditions. It is therefore obvious that when the ifo line is tangent to the qr curve, the critical condition for mixture self-ignition exists. 

The critical condition for explosion is expressed in terms of the dimensionless parameter 6 defined by... 

The stress varies over the sample (compact) surface such that the peak stress is (2 to 2.5)P at the center and Ou/3 at the periphery (where P is the average stress on the sample). Since PCr Ou for most explosives, and the criticality condition is P>PCr, effective hot spots cannot form near the sample periphery. Effective hot spots are also not generated at the center of the sample because inelastic deformation of the sample is a minimum near its center. As will be shown, A B claim that non-uniform inelastic deformation of the entire sample generates hot spots... 

While Gray Yang are not denying the usefulness of such ideas, they consider that too literal an application on the distinction can lead to difficulties. For this reason they tried to unify both theories and this problem is discussed in their paper. They also examined the effect of fuel consumption on thermal explosions, definition of critical conditions and the effects of vessel shapes. Finally, the relationship between thermal explosion criteria and flame theoty described by Belles (Ref 2), as well as detonability limits were pointed out. Comments on the paper of Gray Yang of Profs R.R. Baldwin R. Ben-Aim are given on p 1061 of Ref 3 Refs 1) N.N. Semenov, "Chemical Kinetics... 

Merzhanov Dubovitskii (Ref 4) formulated a general theory for the thermal explosion of condensed expls, which takes into consideration the removal of particles from the reaction volume. This theory makes it possible to calc all the basic characteristics of thermal explosion such as critical conditions, depth of preexplosion decompn induction period "Detonation is Condensed Explosives is the title of a book by J. Taylor (Ref 3) who discusses in detail the various aspects of the subject. See also studies reports listed as Refs 2, 5 6 Refs 1)L.D.Landau K.P.Stanyukovich, Dokl-AkadN 46, 396-98 (1945) 47, No 4, 273 76 (1945) CA 40, 4523 4217 (1946) 2)G.Morris... 

It is obvious that with an insufficient chemical reaction rate we should expect deviations from this picture. By analogy with other combustion and explosion phenomena we may expect that a decrease in the chemical reaction rate with all other conditions equal first only causes some quantitative change—widening of the reaction zone, and then, after some critical value has been reached, the flame will be extinguished, combustion will become impossible and will stop and in its stead mixing of the cold gas and air without any reaction will occur. Below we shall attempt to analyze the critical conditions of quenching in the simplest, schematic case. 

J. Adler and J.W. Enig. The critical conditions in thermal explosion theory with reactant consumption. Combustion and Flame, 8 97-103, 1964. 

In our discussions of branching chain and thermal explosions we examined the critical conditions necessary to establish an explosion in a closed system of finite volume. We saw that, once the critical conditions are at-... 

Detonation of 500-lb Lots of LE-3, An Insensitive Mono-Propellant , NOLTR-68-84 (1968) (ConO J) Anon, Final Phase Report. Part I. Special Warhead , DRD-23 (1968) (ConO K) LA. Karpukhin V.K. Bobolev, Critical Conditions for Explosive Shock Initiation in High Composite Explosives , FizGoreniyaVzryva 3, 381-5 (1967) L) W.H. Snyder C.R. 

Now, every liquid may also have the uniform distribution of internal temperature as a kind of fluid. In other words, as stated in Section 1.5, it will be permitted to say that a condition, UKK A, holds at all times, on account of its own fluidity, in an arbitrary volume of every liquid charged in an arbitrary container and placed in the atmosphere under isothermal conditions. The problem in considering the critical condition for the thermal explosion of a liquid is, thus, not the heat transfer by the convection in the mass of the liquid, but the heat transfer or the heat loss by the conduction from the liquid charged in an arbitrary container and placed in the atmosphere under isothermal conditions, through the whole liquid surface, across the container walls, to the atmosphere. 

CA 64, 12453(1966) (Equation of State and Derived Shock Initiation Criticality Conditions for Liquid Explosives)... 

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