Detonation onset

Smirnov, N.N., V. F. Nikitin, M.V. Tyurnikov, A.P. Boichenko, J.C. Legros, and V.M. Shevtsova. 2001, Control of detonation onset in combustible gases. In High-speed deflagration and detonation Fundamentals and control. Eds. G. Roy,... 

M. Frolov, A.N. Polenov, S.A. Tsyganov, Detonation onset in systems with non-uniform temperature and concentration distribution. Himicheskaya Fizika5(9), 1277-1284 (1986))... 

Distance of deflagration to-detonation transition or pre- detonation distance (FDD) Distance from the flame source to the place of detonation onset. FDD depends on an explosive volume configuration, type of fuel-oxidizer mixture, presence of flow turbulence sources in the path of the flame propagation. 

The preceding section described the state of transition expected in a deflagration process when the mixture in front of the flame is sufficiently preconditioned by a combination of compression effects and local quenching by turbulent mixing. However, additional factors determine whether the onset of detonation can actually occur and whether the onset of detonation will be followed by a self-sustaining detonation wave. 

In a smooth tube, the onset of detonation will take place only if the internal tube diameter is larger than about one characteristic-detonation-cell size. 

Yatsufusa,T., Ghao, J.G., and Lee, J.H.S., The effect of perturbation on the onset of detonation. Proceedings of the 21st International Colloguium on the Dynamics of Explosions and Reactive Systems on GD, Poitiers, 2007. 

Figure 6-21 Explosion data for propane showing peaks indicative of the onset of detonation. Data from W. Bartknecht, Explosions (New York Springer-Verlag, 1981).

With nitrogen iodide, Meerkamper (Ref. 36) found the incident energy indirectly proportional to the time elapsing between the onset of the light flash and detonation. Therefore the relation is ... 

Addition of 3% wax to 470 micron Tetryl at 66.5% TMD increased from about 70mm (no wax) to about 240mm. This is a much greater increase than observed for waxed and unwaxed RDX. Furthermore, addition of wax apparently changes the initial low temp decompn behavior, observed in pure Tetryl, into behavior typical of other expls, in that accelerated burning in waxed Tetryl starts sooner (further away from the onset of detonation) than in pure Tetryl... 

Metal-poor stars Spectral-line comparisons of Cu and of Fe in stars show that the Cu/Fe abundance ratio increased by a factor near 5 while the metallicity of the Galaxy grew during the first billion years. The cause lies either in the increasing yield of Cu from massive stars as they become more metal rich, certainly their s-process component, or in the onset of Type la delayed detonations after the earlier galactic epoch ofType II supernovae only. 

A key point, with regard to both issues, is the decomposition process of the compound What are its energetics and how readily does it occur Our emphasis in this chapter shall be upon factors that influence the ease with which decomposition can be initiated by unwanted external stimuli, i.e. sensitivity. These stimuli may be of various types, including impact, shock, friction, heat and electrostatic charge [8]. Relative vulnerabilities to these different effects need not be the same for example, the onset temperatures for the thermal decomposition of TNT (1) and HMX (2) are quite similar, but the latter is much more likely to undergo detonation upon impact [8]. It has been shown, however, that there is a general correlation between impact and shock sensitivities [10], which are the ones upon which we will focus. 

Instability analyses do not provide good indications of fully developed transverse structures of detonations because these structures correspond to highly nonlinear phenomena. A great deal of nonlinear evolution would occur between onset of instability and attainment of a mature multidimensional detonation structure. Intersections of oblique shocks are known to constitute a central element in transverse structures of detonations [69], [72]. Oblique-shock relations are therefore relevant to the nonplanar structure. 

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