Effect of reflection type on detonation initiation at shock-wave focusing

Bartenev, A. M.; Khomik, S. V.; Gel’fand, B. E.; Grönig, Hans; Olivier, H.

doi:10.1007/s001930050008

Cited by 36 publications

(6 citation statements)

References 5 publications

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“…We note that ignition of detonation by converging shocks has been considered before, in studies of ignition by shock focusing through reflection off concave walls (e.g., Borisov et al 1990;Chan et al 1990;Bartenev et al 2000;Gelfand et al 2000) and by converging toroidal shocks in "pulse detonation engines" (Li & Kailasanath 2003;Jackson et al 2003;Jackson 2005;LI & Kailasanath 2005). However, these studies were mostly experimental, while analytical and numerical investigations were limited to the study of the large-scale behavior of the flow in the experimental setup.…”

Section: Introductionmentioning

confidence: 99%

Imploding Ignition Waves. I. One-Dimensional Analysis

Kushnir

Livne

Waxman

2012

ApJ

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We show that converging spherical and cylindrical shock waves may ignite a detonation wave in a combustible medium, provided the radius at which the shocks become strong exceeds a critical radius, R crit . An approximate analytic expression for R crit is derived for an ideal gas equation of state and a simple (power-law-Arrhenius) reaction law, and shown to reproduce the results of numerical solutions. For typical acetylene-air experiments we find R crit ∼ 100 μm (spherical) and R crit ∼ 1 mm (cylindrical). We suggest that the deflagration to detonation transition (DDT) observed in these systems may be due to converging shocks produced by the turbulent deflagration flow, which reaches sub-(but near) sonic velocities on scales R crit . Our suggested mechanism differs from that proposed by Zel'dovich et al., in which a fine-tuned spatial gradient in the chemical induction time is required to be maintained within the turbulent deflagration flow. Our analysis may be readily extended to more complicated equations of state and reaction laws. An order of magnitude estimate of R crit within a white dwarf at the predetonation conditions believed to lead to Type Ia supernova explosions is 0.1 km, suggesting that our proposed mechanism may be relevant for DDT initiation in these systems. The relevance of our proposed ignition mechanism to DDT initiation may be tested by both experiments and numerical simulations.

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Section: Introductionmentioning

confidence: 99%

Imploding Ignition Waves. I. One-Dimensional Analysis

Kushnir

Livne

Waxman

2012

ApJ

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“…The shock structures produced by the rupture are affected by both the initial geometry of the burst disk at failure (multidimensional) and the (stochastic) fracture geometry, producing shocksidewall and shock-shock interactions (Jiang et al, 1997). It is possible through such shock interactions and ''shock focusing'' (Fay and Lekawa, 1956;Gelfand et al, 2000;Bartenev et al, 2001) exist and produce higher local temperatures and pressures (and hence shorter ignition delays) than those estimated on the basis of simple 1-D theory. Moreover shock interactions with the side walls of the cavity will result in heating the air in the developing boundary layers near the walls and in increasing contact surfaces between the expanding hydrogen core and shock-heated air.…”

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confidence: 99%

Spontaneous Ignition of Pressurized Releases of Hydrogen and Natural Gas Into Air

Dryer

Chaos

Zhao

et al. 2007

Combustion Science and Technology

196

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This paper demonstrates the ''spontaneous ignition'' (autoignition=inflammation and sustained diffusive combustion) from sudden compressed hydrogen releases that is not well documented in the present literature, for which little fundamental explanation, discussion or research foundation exists, and which is apparently not encompassed in recent formulations of safety codes and standards for piping, storage, and use of high pressure compressed gas systems handling hydrogen. Accidental or intended, rapid failure of a pressure boundary separating sufficiently compressed hydrogen from air can result in multi-dimensional transient flows involving shock formation, reflection, and interactions such that reactant mixtures are rapidly formed and achieve chemical ignition, inflammation, and transition to turbulent jet diffusive combustion, fed by the continuing discharge of hydrogen. Both experiments and simple transient shock theory along with chemical kinetic ignition calculations are used to support interpretation of observations and qualitatively identify controlling gas properties and geometrical parameters. Although the phenomenon is demonstrated for pressurized hydrogen burst disk failures with different internal flow geometries, similar phenomena apparently do not necessarily occur for sudden boundary failures potential for producing ignition and continuing combustion. Much more experimental and computational work is required to quantitatively determine the envelope of parameter combinations that mitigate or enhance spontaneous ignition characteristics of compressed hydrogen as a result of sudden release, particularly if hydrogen is to become a major energy carrier interfaced with consumer use. Similar considerations for compressed methane, for mixtures of light hydrocarbons and methane (simulating natural gas), and for larger carbon number hydrocarbons show similar autoignition phenomena may occur with highly compressed methane or natural gas, but are unlikely with higher carbon number cases, unless the compressed source and=or surrounding air is sufficiently pre-heated above ambient temperature. Spontaneous ignition of compressed hydrocarbon gases is also generally less likely, given the much lower turbulent blow-off velocity of hydrocarbons in comparison to that for hydrogen.

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“…The reflection of shock waves from shock tube end walls is a well-established method of initiation [3,4] and is the primary technique used to measure ignition delay times. Several studies have also shown that reflection of a planar incident shock wave from a concave end wall will focus the reflected wave [5][6][7][8], and that the temperatures and pressures at the gas-dynamic focus can be sufficient for initiation of the postshock mixture [9][10][11][12][13][14]. Toroidally imploding shock waves have also been directly initiated from ring sources [15].…”

Section: Previous Research On Imploding Wavesmentioning

confidence: 99%

Detonation Initiation in a Tube via Imploding Toroidal Shock Waves

Jackson

Shepherd

2008

AIAA Journal

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The effectiveness of imploding waves at detonation initiation of stoichiometric ethylene-and propane-oxygennitrogen mixtures in a tube was investigated. Implosions were driven by twice-shocked gas located at the end of a shock tube, and wave strength was varied to determine the critical conditions necessary for initiation as a function of diluent concentration for each fuel. Hydrocarbon-air mixtures were not detonated due to facility limitations, however, detonations were achieved with nitrogen dilutions as large as 60 and 40% in ethylene and propane mixtures, respectively. The critical-energy input required for detonation of each dilution was then estimated using the unsteady energy equation. Blast-wave initiation theory was reviewed and the effect of tube wall proximity to the blast-wave source was considered. Estimated critical energies were found to scale better with the planar initiation energy than the spherical initiation energy, suggesting that detonation initiation was influenced by wave reflection from the tube walls.

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Effect of reflection type on detonation initiation at shock-wave focusing

Cited by 36 publications

References 5 publications

Imploding Ignition Waves. I. One-Dimensional Analysis

Imploding Ignition Waves. I. One-Dimensional Analysis

Spontaneous Ignition of Pressurized Releases of Hydrogen and Natural Gas Into Air

Detonation Initiation in a Tube via Imploding Toroidal Shock Waves

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