Detonation propagation

The other detonability length scale is the detonation cell width, X (also called cell size) which is the transverse dimension of diamond shaped cells generated by the transverse wave stmctnre at a detonation front. It has a fish scale pattern (see Figure 4-4). Detonation cell widths are nsnally measured by the traces (soot) deposited on smoke foils inserted in test vessels or piping surfaces. The more reactive the gas-air mixture, the smaller is the cell size. The same is tme for chemical indnction length as a qualitative measure of detonability. The cell width, X, is a parameter that is of practical importance. The transition from dehagration to detonation, propagation, and transmission of a detonation, can to some extent be eval-... 

Tims it is possible to estimate order of magnitnde limits for detonation propagation nsing calcnlated CJ indnction zone lengths or measnred cell size data. These were limits for established detonations propagating into pipes of decreasing diameter. Variations in the detonability of different mixtnres in different pipe geometries are thns intimately linked to the initial chemical and physical properties of the mixtnre. 

Detonation Propagation of a flame-driven shock wave at a velocity at or above the speed of sonnd in the nnreacted medinm as measnred at the flame front. The wave is snstained by chemical energy released by shock compression and ignition of the nnreacted medinm. The flame front is conpled in time and space with the shock front, and there is no pressnre increase significantly ahead of the shock-flame front. Propagation velocities in the range 1000-3500 m/s may be observed depending on the gas mixtnre, initial temperatnre and pressnre, and type of detonation. 

Critical Diameter. The crit diam for deton propagation in iron tubes is 25mm, in brass 7mm (Ref 31)... 

Analytical A proc is described for the quant titrimetric analysis of TeNMe in nitric acid (Ref 35)s and a spectrophotometric method is described in Ref 41 for the detn of small amts of TeNMe in air and w Critical Diameter. The crit diam for deton propagation of TeNMe thickened with poly-(methyl acrylate) and loaded with up to 75% inert solids was detd and found to decrease with increasing solids loading. It was postulated that the solids acted as reaction foci ahead of the deton front (Ref 45)... 

The instability and nonplanar character of the detonation front was first exhibited by Manson [1] and Fay [2] in certain particular cases of detonation propagation, such as fhe "spinning detonations." The multidimensional nature of the detonation front has been established by Voitsekhovskii [3], Denisov and Troshin [4],... 

In Chapter 8.5, B. Veyssiere exposes the state of knowledge in detonations. Particular features of the complex multidimensional structure of detonations are presented in relation with the recent results obtained either by nonintrusive optical diagnostics or numerical simulations from high performance calculations. The role of transverse waves in detonation propagation, the existence of correlations between the characteristic dimension of the cellular structure and the critical conditions for detonation initiation and detonation transmission, and the influence of the nonmonotonous heat release process behind the front are examined. Recent developments in the study of spinning detonations are also discussed. 

The major chemical components of emulsion explosives are fundamentally the same as those of slurry explosives, as shown in Table 9.4.[i l Instead of the sensitizers used for slurry explosives, a large number of hollow microspheres made of glass or plastics are incorporated to formulate emulsion explosives in order to obtain successive detonation propagation after the initiation of detonation. During detonation propagation into the interior of the explosives, an adiabatic compression results... 

Dunkle (Ref 3) made the following r emark "I hate to disagree with Cook, but I would call a detonation propagating at less than sonic velocity a deflagration. Evidently the wave sets up sound waves ahead which go at successively faster rates, thus telescoping into a shock wave which initiates detonation some distance ahead of the low-velocity wave ... 

As the wave evolves from that point, the losses connected with rearward expansion decrease. If a charge of a small diam is considered, then lateral expansion depends on the path over which the wave has traveled. The increase in cross section of a cylinder, i.e., expansion in the lateral direction, leads to a reduction in pressure and to a decrease in the deton velocity in comparison with detonation propagating in a constant cross-section cylinder. The decrease in deton vel causes, in turn, the diminution of shock amplitude wave and impairs the conditions under which the reaction can proceed. The loss caused by lateral expansion is known as lateral loss. Propagation of detonation is possible only if this loss is not smaller than a certain limit, which is characteristic for each expl... 

Detonation, Propagation Failure of was discussed by B.E. Drimmer T.P. Liddiard in "Propagation Failure in Explosives Under Dynamic Precompression , USNavalOrdnance Laboratory, White Oak, Silver Spring, Md, NOL TR 64-40, July 1964... 

The upper end of column was provided with a Fuze. If deton propagated whole length of the column, an impression was made on the steel plate... 

In mixtures near the limit, the shock wave and the flame separate momentarily, and the gases behind the shock are then the seat of vibratory phenomena, not only transverse but also longitudinal (of the same frequency as in the burnt gases). It would appear from this that such phenomena, but at even higher frequency, exist in the gas layer separating the shock wave and the flame of detonations propagating under conditions far removed from the limits, and that they play an important role in the coupling of the shock and the flame... 

Accdg to Price (Ref 15), in studying shock-to-detonation transitions a frequent question is whether a certain expl is extremely insensitive to shock or is, in fact, nondetonable under the test conditions. To answer it, some investigation must be made of the critical diam (dc) of cylindrical chges, i.e., that diam above which, deton propagates and below which deton fails. The loading density rather than the diam can be varied in that case, the critical density (pc) is detd. Pairs of such values form the detonability limit curve which divides the d—vs—p plane into one region where deton can occur and another where it must fail. 

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