Jumping detonation

Definition of deton, expln de-flgrn) 44-8 (Ideal deton) 48-50 (Nonideal deton) 50-7 (Transient and unstable deton waves) 57-60 (The jumping deton) 61-90 (Thermohydrodynamic theory of deton) 61-6 (Equation of state in deton of condensed expls) 66-8 (The Chapman-Jouguet postulate) 68-75 (The deton reaction zone in gases) 75-7 (Reaction zone in nonideal deton in gases) 77-9 (Reaction zone in condensed expls) 79-87... 

It is stated that the AN-coarse TNT-water slurries all detonate in the transient detonation region by the jumping detonation reaction)... 

The conditions responsible for the jumping detonation are evidently those for propagation of deton thru inert media such as glass and steel in which the shock wave first outruns the reaction and is then suddenly overtaken after the chemical reaction has finally built to a critical stage in which.a heat pulse is able to propagate (Ref 52, p 59)... 

Jumping Detonation. See Detonation, Jumping in Vol 4 of Encycl, p D421-L... 

If a chge is initiated in a narrow tube, its low deton vel will jump to the high one when the wave reaches the large diam tube... 

To achieve high-order detonation in secondary explosives, it has always been necessary to allow much longer delays in order to let the low-order process initially started "jump to high order [Compare with Detonation (and Explosionjby Influence] Note 2 In a review of 23 papers on initiation, ignition, and growth of reaction presented at the 4thONRSympDeton bv G.P. 

The pressure "jump necessary to initiate detonation in various expls does not belong under this heading. This has been discussed under "Detonation (and Explosion Initiation - - - - in Explosive Substances . The actual value of the required "jump seems to be 25-50 atm (Ref 9). 

Majnwica Jacobs (Ref 16) reported a jump (overshoot) from below to normal detonation velocity in a number of cased expls in other expls the velocity grew continuously from a low value to that of normal deton. 

Detonation Wave, Jumping. See p D421 and in Ref 52, pp 57-9, listed on p D727... 

Only the tangent point B satisfies both conditions at once it may be attained in the process of chemical reaction of a gas which is compressed by a shock wave (the jump HY and the drop YB), and at the same time the state B is compatible with the conditions of expansion of the detonation products upon completion of the reaction (the detonation velocity in state B is exactly equal to the velocity of propagation of a perturbation in the reaction products). 

At a larger detonation velocity, after the jump AH, motion occurs along the segment HF, and the impossibility in detonation of landing at the point G of the lower branch BGI thus follows directly from the mechanism of a chemical reaction which requires shock compression with a subsequent smooth slide along the Todes line in order to begin. Jump-wise motion... 

The line M2 — H2 is a singularity line of the equation (dotted line, Fig. 5). By defining detonation as a regime in which flame propagation occurs at a velocity greater than the speed of sound in the original gas, we find at the point A c < D c2Jv2 < D2/v2, H2 < M2. After the shock compression, at the point C, as we know, c > D, H2 > M2 the shock compression is accompanied by a jump across the line M = H. 

The beginning of reaction in a detonation wave is related to compression and heating of the gas by a shock wave (the jump from A to C, Fig. 1 or 5). Let us consider the conditions of occurrence of the chemical reaction, accompanied by a change in the state which more or less closely follows the equation of the Todes line. 

The front of the detonation is a jump discontinuity and therefore can be handled in the same manner as the one we used with nonreactive shock waves. 

Let us look at the detonation jump condition on the P-v plane, Figure 20.1. As you can see in this figure, we are dealing with two materials in a detonation jump condition, the unreacted explosive and the completely reacted gaseous detonation products. Not only are we jumping from one physical state to another, but also to a new chemical state. In this figure, we see the initial state at point A, the unreacted explosive we see also the state at point C the jump condition to the fully shocked but as yet unreacted explosive and on another Hugoniot, the state B of the reaction products. 

Just as with shock waves (nonreacting), the detonation is a jump process and is handled the same as shock waves are on the P-u plane. The detonation jump condition from the state of an unreacted explosive to the CJ state is the straight line joining those two states. The difference here is that state zero is the solid HE, and the CJ state is on the product Hugoniot. The initial unreacted state, if we assume o = 0, is at the P = 0, m = 0 origin on the P-u plane. Figure 20.8 shows the detonation jump condition. Where the slope of the jump line for nonreactive shocks was poU, the slope of the jump line for a detonation is poD. 

Although the effect is small, raising the initial temperature of an explosive decreases its detonation velocity and vice versa. Data for some explosives have been measured and are presented in Table 21.8. There are sufficient data on such properties as Cp, a (linear temperature expansion coefficient), A//d (heat of detonation), po, P, and D to calculate this effect using the jump equations and simple thermophysics (Ref. 5 lists such data) for many explosives. Typically, AD/AT), the change in detonation velocity per unit change in temperature, will be found to be in the range of from -0.4 X 10 to -4 x 10 (mm/p,s)/(°C). 

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