Spontaneous initiation of detonations

Bartenev, A. M.; Gel’fand, B. E.

doi:10.1016/s0360-1285(99)00007-6

Cited by 71 publications

(17 citation statements)

References 40 publications

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“…for the belief that a good deal of the actual DDT dynamics is captured quite adequately. The DDT problem therefore turns out to be physically related to the shockless (soft) initiation of detonation in non-uniformly preheated gas, a topic that has enjoyed much attention in the recent past (see [5,13] and references therein). Unlike the latter systems, however, in the DDT case, the non-homogeneous environment that provides the required spatial gradient of the induction time is not prescribed but arises as a product of the flameconfinement interaction.…”

Section: Overviewmentioning

confidence: 99%

Combustion waves in hydraulically resisted systems

Brailovsky

Kagan

Sivashinsky

2012

Phil. Trans. R. Soc. A.

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The effects of hydraulic resistance on the burning of confined/obstacle-laden gaseous and gas-permeable solid explosives are discussed on the basis of recent research. Hydraulic resistance is found to induce a new powerful mechanism for the reaction spread (diffusion of pressure) allowing for both fast subsonic as well as supersonic propagation. Hydraulic resistance appears to be of relevance also for the multiplicity of detonation regimes as well as for the transitions from slow conductive to fast convective, choked or detonative burning. A quasi-one-dimensional Fanno-type model for premixed gas combustion in an obstructed channel open at the ignition end is discussed. It is shown that, similar to the closed-end case studied earlier, the hydraulic resistance causes a gradual precompression and preheating of the unburned gas adjacent to the advancing deflagration, which leads (after an extended induction period) to a localized autoignition that triggers an abrupt transition from deflagrative to detonative combustion. In line with the experimental observations, the ignition at the open end greatly encumbers the transition (compared with the closed-end case), and the deflagration practically does not accelerate up to the very transition point. Shchelkin's effect, that ignition at a small distance from the closed end of a tube facilitates the transition, is described.

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Section: Overviewmentioning

confidence: 99%

Combustion waves in hydraulically resisted systems

Brailovsky

Kagan

Sivashinsky

2012

Phil. Trans. R. Soc. A.

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“…The DDT problem therefore transpires to be physically related to the shockless initiation of detonation in non-uniformly preheated gas, a topic that has been energetically explored in recent years [8][9][10][11][12][13][14][15][16][17]. Unlike the latter systems, however, in the DDT case, the nonhomogeneous environment that provides the required spatial gradient of the induction time is not prescribed but arises as a product of the flame-confinement interaction.…”

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confidence: 99%

On the Transition from Deflagration to Detonation in Narrow Tubes

Kagan

Sivashinsky

2010

Flow Turbulence Combust

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The paper is an extension of our recent work on the deflagration-todetonation transition in narrow channels over the transition in narrow circular tubes under more realistic point ignition conditions. The changes from channel to circular tube geometry and from planar to point ignition result in enhancement of the incipient acceleration of the flame and reduction of the predetonation time and distance.

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“…It may not take much lateral heat transport to ignite neighboring fuel pockets and the ignition may quickly spread over the NS. This is not a detonation, but it may have similar spread velocities (this so-called auto-or selfignition is discussed for chemical combustibles in, e.g., Frolov et al 1992;Makhviladze & Rogatykh 1991;Bartenev & Gelfand 1990). In this scenario, the distinguishing factor of bursts with fast rises from those with slow rises would be the strong lateral homogeneity in the temperature distribution.…”

Section: T Spreadmentioning

confidence: 99%

Relativistic outflow from two thermonuclear shell flashes on neutron stars

Zand

Keek

Cavecchi

2014

A&A

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We study the exceptionally short (32-43 ms) precursors of two intermediate-duration thermonuclear X-ray bursts observed with the Rossi X-ray Timing Explorer from the neutron stars in 4U 0614+09 and 2S 0918-549. They exhibit photon fluxes that surpass those at the Eddington limit later in the burst by factors of 2.6 to 3.1. We are able to explain both the short duration and the super-Eddington flux by mildly relativistic outflow velocities of 0.1c to 0.3c subsequent to the thermonuclear shell flashes on the neutron stars. These are the highest velocities ever measured from any thermonuclear flash. The precursor rise times are also exceptionally short: about 1 ms. This is inconsistent with predictions for nuclear flames spreading laterally as deflagrations and suggests detonations instead. This is the first time that a detonation is suggested for such a shallow ignition column depth (y ign ≈ 10 10 g cm −2 ). The detonation would possibly require a faster nuclear reaction chain, such as bypassing the α-capture on 12 C with the much faster 12 C(p, γ) 13 N(α, p) 16 O process previously proposed. We confirm the possibility of a detonation, albeit only in the radial direction, through the simulation of the nuclear burning with a large nuclear network and at the appropriate ignition depth, although it remains to be seen whether the Zel'dovich criterion is met. A detonation would also provide the fast flame spreading over the surface of the neutron star to allow for the short rise times. This needs to be supported by future two-dimensional calculations of flame spreading at the relevant column depth. As an alternative to the detonation scenario, we speculate on the possibility that the whole neutron star surface burns almost instantly in the auto-ignition regime. This is motivated by the presence of 150 ms precursors with 30 ms rise times in some superexpansion bursts from 4U 1820-30 at low ignition column depths of ∼10 8 g cm −2 .

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Spontaneous initiation of detonations

Cited by 71 publications

References 40 publications

Combustion waves in hydraulically resisted systems

Combustion waves in hydraulically resisted systems

On the Transition from Deflagration to Detonation in Narrow Tubes

Relativistic outflow from two thermonuclear shell flashes on neutron stars

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