Detonation velocity estimation

In this writer s opinion, Cook s values (Table 12.20 of Ref 18a) of TCJ are too high and his Pfj are too low the products probably contain more free carbon than shown. However, there is little doubt that most LOX detonations are hot , ie, they will readily ignite firedamp (Refs 2, 3, 12 14). Also the computed detonation velocities (estimated from Cook s PCj) show a much greater variation with compn and density than the experimental data of Table 3... 

The calculated detonation velocity in room temperature acetylene at 810 kPa is 2053 m/s (61). Measured values are about 1000-2070 m/s, independent of initial pressure but generally increasing with increasing diameter (46,60—64). In a time estimated to be about 6 s (65), an accidental fire-initiated decomposition flame in acetylene at ca 200 kPa in an extensive piping system traveled successively through 1830 m of 76—203-mm pipe, 8850 m of 203-mm pipe, and 760 m of 152-mm pipe. 

A semi-empirical method for estimating the detonation velocities of explosives composed of C, H, N, and O atoms has been proposed.PI The heat of detonation per mole, AHd, defined by... 

Dr Price also examined relations between (A) and deton velocity (D). They are presented in Fig 3 for group 1 and in Fig 4 for group 2 Fig 3 shows a representative of group 1, an unconfined cylindrical charge of HBX-1 (RDX/TNT/A1/Wax - 40/38/17/5). Its voidless density is 1.76 g/cc. The curves are for charge diameters d, d, d d which are 6.4, 12.7, 25.4 50.8 mm, respectively. Solid lines are smoothed values from the experimental data which have been extrapolated to A=0.6. The limit line for failure was estimated, as shown on p 694 of Ref 17. A pattern of the same type was previously obtd by Stesik Akimova (Ref 3) for TNT... 

In an effort to understand the formidable-appearing output of many computations for a wide variety of C-H-N-O explosives at various initial loading densities, we have investigated interrelationships between such properties as pressure, velocity, density, heat of reaction, etc. These studies have led to a number of interesting observations, important among which were the facts that much simpler semiempirical formulas could be written for desk calculation of detonation velocities and detonation pressures, with about the same reliance on their answers as one could attach to the more complex computer output. These equations require as input information only the explosive s composition and loading density and an estimate of its heat of formation, and, in their comparative simplicity,... 

There are some simpler methods which can be applied for the rough estimation of detonation velocity one such method is known as the Dautriche method . This simple method does not require the use of any special or costly instrument. The determination of detonation velocity is based on the fact that the processes that propagate at different linear velocities travel different distances in the same time. The difference in length of the distance traveled is a simple function of the velocities of these two processes. This method is mainly used for the determination of detonation velocity of commercial explosives. However, the same principle can be applied in order to determine detonation velocities of military explosives. The accuracy of the data obtained by this method is -4—5%. The Dautriche method for the determination of VOD of explosives as described by Meyer [80] is illustrated in Figure 3.20. 

Sometimes the plate around the dent was colored blue. Stettbacher claimed that the deeper the dent the more powerful was the expl and that the brisance and detonation velocity may be approx estimated by the appearance of the surface of the plate. The deeper the blue color and the coarser, more numerous and deeper stratiations, the greater was the brisance and the higher was the deton velocity. The total energy was expressed in mm of depth of the dent... 

In assessing the potential value of a proposed energetic compound, important measures of performance are detonation velocity and pressure for explosives and specific impulse for propellants. One of the key factors in determining these properties is the energy that is produced in the decomposition or combustion process [1-4]. This can normally be estimated if the compound s heat of formation, AHf, is known. (There are also indications that the energy of decomposition is related to sensitivity toward initiation of detonation [5,6].) Thus a reliable value for AHf is essential to the evaluation of a compound. If the latter has not yet been synthesized, then its heat of formation must necessarily be obtained by a computational procedure. This may be true as well if only a very small amount has been prepared, or if the laboratory determination presents difficulties [7]. 

The determination of the maximum detonation pressure pi, in equation (2d) has been studied by X ray measurements. While the detonation velocity can be measured directly by electronic recorders or by the - Dautriche Method, there is no direct measurement possibility for the fume velocity W, but it can be estimated by the flow off angle of the fumes behind the wave front this angle can be taken from X ray flash photographs. The relation between Dand M/is... 

The thermodynamic data as well as the detonation parameters can nowadays be very reliably obtained by using quantum-mechanical computer calculations. On the one hand it is important to check experimental results, and on the other hand and even more importantly - it is important to predict the properties of potential new energetic materials without any prior experimental parameters, for example during the planning of synthetic work. Moreover, such computational methods are ideal for the estimation of the detonation parameters of newly synthesized compounds, which have not been obtained in the 50 100 g quantities which are necessary for the experimental determination of such detonation parameters (e.g. detonation velocity). 

According to Kamlet and Jacobs the detonation velocity (D) and the detonation pressure (pc.j) can be estimated. Give the relevant equations. 

Detonating velocity Uncalculated (6500 estimated) Toxicity High... 

Detonating velocity 7800 (estimated) also 7300 (estimated) Toxicity Moderate... 

Detonating velocity 7200 (estimated) also reported as 7300 Toxicity Above Moderate... 

The references listed at the end of this section are excellent sources for properties data for many explosives. However, if those references are not available, or if properties data for new or proposed explosive compounds are required, then some means of reasonably estimating the values must be used. In this chapter we will explore some surprisingly accurate methods of estimating the theoretical maximum density (TMD) of an explosive as well as its detonation velocity at TMD, knowing only the structural formula for the explosive compound. Further, we will be able to estimate the detonation velocity at densities other than at TMD, once that value is knowTi and also, once having found the detonation velocity and density, we can estimate the detonation (or Chapman-Jouguet, CJ) pressure from those values. 

We have just seen how to estimate p(TMD) and ) (Z) at TMD) from the chemical structure of an explosive molecule. That is a lot of estimating power. Another tool to add to this kit is estimation of D for mixtures of explosives. In the 1940s, Maimy Urizer at Los Alamos Scientific Laboratory found that by adding the detonation velocity on a partial volume basis one could arrive at the D for a mixture (Ref. 4). 

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