Detonation initiation

Small amts of moisture can also affect expl performance. As little as 0.5% can cause unpredictable deton initiation and randomly variable deton vels, which could defeat the efficient use of an expl in, for example, a shaped charge application (Ref 26). See also Vol 4, D347-L D356-R... 

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)... 

Threshold for Detonation Initiation in Uncon-fined Fuel-Air Mixtures , 4th Intern Colloq... 

Detonation initiation resulting from shock reflection or shock focusing... 

The studies by Teodorczyk et al. [40-42] and Chan et al. [30] conclusively demonstrated that the mechanism of detonation initiation in quasi-detonation regime is owing to autoignition via shock reflections. These studies show that normal shock reflections from the obstacle, Mach reflection of the diffracted shock on the bottom... 

Khokhlov, A.M. and Oran, E.S., Numerical simulation of detonation initiation in a flame brush The role of hot spots. Combust. Flame, 119, 400, 1999. 

Temperature field obtained by numerical simulations [23] behind the front of a fully developed (0.3 ms after the detonation initiation) detonation in hydrogen/air at 1 atm. Minimum computational cell size is 5 pm. (Courtesy of V. Gamezo.)... 

Soot patterns showing the predetonation radius in hemispherical critical detonation initiation of C2H2 + 2.5O2 mixture at 30 torr initial pressure. (Courtesy of D. Desbordes.)... 

For classical hydrocarbons, the value of K is, according to Desbordes [25], approximately K.=20. In the same way, correlations between the critical energy for direct detonation initiation and the dimension of the cell width have been proposed by different authors [25-27]. 

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 theory of detonation has also been extended to study the process of initiation of reaction by the commonest means used in practice, namely, by the shock wave arising from another high explosive. Campbell, Davis and Travis have studied the initiation by plane shock waves of homogeneous explosives, particularly nitromethane. Initiation occurs at the boundary of the explosive after an induction period which is of the order of a microsecond and which depends markedly on initial temperature. During the induction period the shock wave has proceeded through the explosive and compressed it. The detonation initially in compressed explosive has a velocity some 10% above normal, but the detonation soon overtakes the... 

Gelatine explosives, initiated by commercial detonators, will normally fire at the low velocity of detonation initially, although this may well build up quite quickly into the high velocity. For some applications a high velocity of detonation is essential. This can be ensured by the addition of barium sulphate, or other material with density exceeding 2-8, in a fine form. Such additives have the property of ensuring rapid transition to the high velocity of detonation. This is, for example, of particular importance when the explosive is to be fired under a hydrostatic head, as in submarine work. 

Refs 1) B. Lewis G. von Elbe,. Combustion, Flame, and Explosion of Gases , Oxford Univ Press, London (1938) la) K.I. Shchelkin, DoklAkadN 23, 636(1939) (On the theory of detonation initiation for gaseous mixtures in pipes) lb) K.I. Shchelkin, ZhEksper i TeoretFiz 10, 823(1940) (The effect of rough-... 

Blasting Caps and Detonators, Initiating Efficiency of. See under Initiating Efficiency Tests in Vol 1, p XVIII... 

Initiating Efficiency (or Strength) of Detonators by the Miniature Cartridge Test. See Vol 1, p XVtfl and R.L. Grant J.E. Tiffany, "Detonators Initiating Efficiency by the Miniature-Cartridge Test , USBurMines-TechPaper 677(1945)... 

On the theory of detonation initiation of gaseous mixts in pipes)... 

Detonation Initiation , AIAA-J 2, 783-84 (April 1964) 26) T. Asaba et al, "Shock... 

The quantitative requirements as in the onedimensional case, are determined by the reaction kinetics, the physical state, and the equations of stat e of the material or of its components if the chge is heterogeneous. The shock- terminating rarefaction is here provided by the three- dimensional geometry and does not need a pressure-relieving rear boundary condition as in the one-dimensional case. If the shock wave is inadequate for detonation initiation, a deflagration frequently occurs instead. In Section VI,B of Ref 66, it was shown that for the correct boundary conditions a deflgrn can create a shock wave which can initiate a deton... 

The mine is buried underground, near the surface and when somebody steps on pressure plate, the firing pin detonates initiating charge of the fuze primer and the shock is transmitted to Tetryl charge of the mine... 

Ishpeming, Mich - Water gel Kenvil, N J — Smokeless powder, diazo Louisiana, Mo — Ammonium nitrate, nitric acid Parlin, N.J — Nitrocellulose Port Ewen, NY— Detonators, initiators Rocket Center, W Va - Propellants Radford, Va — Government owned, company operated... 

For a running detonation, ie detonation initiated at one end of a HE slab, the velocity v it imparts to a plate of mass m, where the other face of the explosive slab is bounded by another plate of mass m , is given by ... 

Thus gas detonations initiate condensed explosives (if at all) by some direct heat transfer process. In oxy-acetylene detonations, the equilibrium temperature (CJ temp) is quite high 4500°K... 

LOX are sensitive to sympathetic detonation, ie, detonation initiated by a nearby charge separated from the LOX by an air gap (Refs... 

Impact Sensitivity — less sensitive than PA and TNT FI 120% PA. French test with 10kg weight (mouton) gave at the height of drop 2.50 meters, 50% detonations Initiation Sensitivity — 50g sample pressed to sp gr 1.23 in a paper cylinder 30mm diam required 2g MF for its detonation Power (Strength) — si more powerful than TNT, but less powerful than EDNA. Ballistic Mortar... 

EXPLOSION (AND DETONATION), INITIATION (BIRTH), AND PROPAGATION (GROWTH OR SPREAD) in EXPLOSIVE SUBSTANCES. See... 

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