Heterogeneous Detonations

The 50 kbar shock grows and detonation occurs at 0.390 cm in 0.83 nsec. A long duration pulse would result in detonation at 0.386 cm in 0.736 sec. The 40 kbar shock does not grow to detonation as the rear rarefactions remove energy from the shock front as fast as it is generated by the hot spots. 

Modeling using Forest Fire reproduced the observed quantitative behavior of the shock initiation by short pulses of PBX-9404 and Composition B. The energy available from shocked and decomposing explosive that has not detonated is important for vulnerability modeling. 

Forest Fire has been successfully applied to many explosives and shock-sensitive propellants. The results are sensitive to the Pop plot, and small experimental errors at low pressures can be magnified in the rate sufficiently to cause large errors in the calculated time histories of a building shock wave. For example, the PBX-9404 that Kennedy used for some of his experiments was slightly different from the type described in this chapter. Unfortunately different batches of the same explosive can have different void distributions even at the same density and hence have different Pop plots. 

As shown in reference 29, if the Pop plot for an explosive is known, it is possible to estimate the Pop plot for other densities. The Pop plot for an explosive can be estimated if gap sensitivity data are available for the explosive by using the Pop plot for an explosive with the same gap sensitivity. 

The Los Alamos National Laboratory radiographic facility, PHERMEX, has been used to study detonation wave profiles in heterogeneous explosives as they proceed up metal surfaces . PHERMEX has also been used to study the density profiles when a detonation wave turns a corner. 

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Solid particle-gaseous oxidizer systems have been studied because of applications to propints and expls (Refs 5 14), and hazards due to dust explns (Refs 1,3, 4, 6, 7, 10 15). Strauss (Ref 9) reported on a heterogeneous detonation in a solid particle and gaseous oxidizer mixt the study concerned A1 powder and pure oxygen in a tube. Detonations initiated, by a weak source were obtained in mixts contg 45-60% fuel by mass. Measured characteristics of the detonations agreed with theoretical calcns within about 10%, and detonation pressures of up to 31 atms were observed. With regard to solid particle-air mixts, detonations have not been reported only conditions for expln have been studied (Ref 2)... 

The former, at 15 bar initial oxygen pressure gave 1 kbar/s rise to 75 bar maximum, but at 20 bar a transition to 21 kbar/s to 121 bar maximum occurs, and at 30 bar to 90 kbar/s and 160 bar maximum is observed, the latter almost certainly involving heterogeneous detonation on the wick and shattering of the containing crucible. Pentamethyldisiloxane at 25 bar initial oxygen pressure shows a rate of rise of 60 bar/s to maximum 49 bar, but at 30 bar initial pressure the rate increases to 38 kbar/s to 205 bar maximum. 

Roy, G.D., S.M. Frolov, K. Kailasanath, and N. Smirnov, eds. 1999. Gaseous and heterogeneous detonations Science to applications. Moscow ENAS Publ. 

Frolov, S.M., V. Ya. Basevich, A. A. Belyaev, and M. G. Neuhaus. 1999. Application of fuel blends for controlling detonability in pulsed detonation engines. In Gaseous and heterogeneous detonations Science to applications. Eds. G.D. Roy, S.M. Frolov, K. Kailasanath, and N. N. Smirnov. Moscow ENAS Publ. 313-30. 

The author concludes that the partides create addnl hot spots which serve to shorten time-to-deton because a heterogeneous deton front results. The effect of the degree of dispersion of the particles is shown by a parabolical plot of the critical diam in mm versus the wt % of W powder data. From the parabolic shape of this curve the author further concludes that the more partides present beyond a certain point, the less efficient the individual hot spots become and, ergo, the greater the critical diam for deton. Indeed, extension of the plotted data beyond the measured data for over 60 wt %W indicates a substantial increase in critical deton diam over pure Nitromethane. This effect is attributed to the formation of heat sinks by the W particles in... 

Charles L. Mader and Charles A. Forest, Two-Dimensional Homogeneous and Heterogeneous Detonation Wave Propagation , Los Alamos Scientific Laboratory report LA-6259 (1976). 

Gordopov, Y.A., Batsanov, S.S. and Trofimov, V.S. (2009) Shock Induced Solid-Solid Reactions and Detonations, in Shock Wave Science and Technology Reference Library, Heterogeneous Detonation (ed. F. Zhang) Springer, New York, 4, 287-314. 

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