Metalized heterogeneous detonation and dense reactive particle flow

Zhang, Fan

doi:10.1063/1.3686215

Cited by 11 publications

(13 citation statements)

References 5 publications

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“…At higher dispersal speeds, the droplet or particle cloud is highly perturbed and coherent jet structures form during the expansion (see Fig. 1) [6][7][8][9][10][11][12][13][14]. The formation of particle clusters and jets is widely observed in nature, with examples such as supernovae, volcanic eruptions, embedded landmine explosions and shallow underwater explosions.…”

Section: Introductionmentioning

confidence: 99%

“…The experimental initial particle expansion velocity was found to be related to the so-called "Gurney velocity", which is determined from both the explosion energy and mass ratio of dispersal payload to explosive. Through meso-scale simulations Xu et al [12,13] indicated that micro-jets of detonation products are developed due to the non-uniform density effect at the multiphase interface between the center explosive and the surrounding packed particle bed; this could lead to one of the origins of jetting formation.…”

Section: Introductionmentioning

confidence: 99%

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Large-scale spray detonation and related particle jetting instability phenomenon

et al. 2014

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The detonation performance of a more than 70,000 m 3 fuel spray-air cloud is experimentally investigated using dispersal of a 5,090 kg gasoline payload by a central explosive in a cylindrically stratified configuration. The large-scale explosive dispersal data are further analyzed, together with a revisit of the data from previously conducted small-scale experiments and numerical simulations, to study particle jetting instabilities. The experiments depict a dual hierarchical jet structure consisting of primary particle jets overlapped by fine particle jets on the primary surfaces. Both jet systems form within the expansion of 1.5-2 times the initial charge diameter. The fine droplet jets are numerous initially as a result of surface instabilities or fragmentation of the charge casing, while the primary jets have a limited number emerging out of the surface of fine jet structures later in time. The number of primary jets is consistent with the number of incipient radial fractures observed at the payload surface. From this fact, an instability mechanism is suggested that the formation of primary particle jets may originate in the perturbations that develop near the interior interface between explosive and payload, through non-uniform density effects or casing fragmentation, driven by the explosive detonation and subsequent expansion of the high-pressure detonation products. Numerical modeling using liquid payload fragmenting into droplet particles has been applied to investigate the proposed mechanism. The numerical results show that the high-pressure jets of detonation products, created from the interior casing fragmentation, radially fracture the payload. The resulting compressed radial filaments, developed within the payload, lead to the primary jets emerging between the radial fracture points at the payload surface. The number of interior payload filaments before payload surface bursting, and hence the number of primary jets, is controlled by the number of inner casing fragments at the explosivepayload interface. Furthermore, the number of primary jets is also influenced by the mass ratio of payload to explosive and inner casing fragment pattern, whereas the perturbations induced by minor fragments will dissipate through the large payload and not result in final filaments.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Large-scale spray detonation and related particle jetting instability phenomenon

et al. 2014

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“…The second characteristic is that the combustion will generate solid Al 2 O 3 , which may further influence detonation product expansion. These multi-phase interactions make Al combustion very complicated, resulting in many unresolved problems [5,6].…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of one-dimensional aluminum particle–air detonation with realistic heat capacities

Teng

Jiang²

2013

Combustion and Flame

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a b s t r a c t Aluminum (Al) particle-air detonation is very complicated because it includes multi-phase combustion phenomenon. Thus numerical simulations are often over-simplified. Here, the detonation is simulated by solving one-dimensional equations with more realistic heat capacities that vary with the dust mixture temperature. The effect on detonation parameters from the realistic heat capacities for the solid particles is investigated with a hybrid combustion model. The calculated results indicate that the detonation pressure, temperature and velocity vary significantly with changes in the heat capacity. Except for the velocity, these parameters are overestimated in numerical simulations when a constant heat capacity of the pre-shock mixtures is used. Furthermore, the realistic heat capacities have a strong effect on small diameter particles, but a weak effect on large diameter particles. Thus, when constant heat capacities are used, the combustion characteristic lengths are a function of the particle diameters with a power dependence of 1.77, whereas the power dependence decreases to 1.49 when realistic heat capacities are used. Moreover, if realistic heat capacities are applied, an ''abnormal'' strong detonation wave may appear in a dust mixture having large diameter particles. This phenomenon is consistent with the current combustion model, but it indicates that the value of heat released should also vary with the gas temperature in a fashion similar to that of the heat capacities.

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“…Interestingly, the failure along the wafer edge does not occur uniformly, but instead occurs locally forming discrete particle jets. These jets associated with the failure of the wafer are analogous with the jets that form in large-scale multiphase explosions [3,8]. The spherical expansion of the solid explosives does not generate shear in the surrounding packed particle bed shell, instead the outward radial motion results in a circumferential tension in the particle shell.…”

Section: Downstream Surface Visualizationmentioning

confidence: 99%

“…The shock wave initially propagates through a granular particle bed and much later after the passage of the shock wave, the particles are further dispersed by the radial combustion product flow forming a cloud. In this application it is important to understand the dispersion of the particles as the energy release from the particles maintains the pressure in the shock sphere, thereby increasing the shock wave impulse [3]. The particle dispersion phenomenon varies from early time when the particle volume fraction is large, to later time where the volume fraction is very small and the flow is considered a dilute gas-solid flow, i.e., similar to a dusty-gas flow.…”

Section: Introductionmentioning

confidence: 99%

Dense Particle Cloud Dispersion by a Shock Wave

Kellenberger¹

2012

28th International Symposium on Shock Waves

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A dense particle flow is generated by the interaction of a shock wave with an initially stationary packed granular bed. High-speed particle dispersion research is motivated by the energy release enhancement of explosives containing solid particles. The initial packed granular bed is produced by compressing loose powder into a wafer with a particle volume fraction of Φ = 0.48. The wafer is positioned inside the shock tube, uniformly filling the entire cross-section. This results in a clean experiment where no flow obstructing support structures are present. Through high-speed shadowgraph imaging and pressure measurements along the length of the channel, detailed information about the particle shock interaction was obtained. Due to the limited strength of the incident shock wave, no transmitted shock wave is produced. The initial "solid-like" response of the particle wafer acceleration forms a series of compression waves that eventually coalesce to form a shock wave. Breakup is initiated along the periphery of the wafer as the result of shear that forms due to the fixed boundary condition. Particle break-up is initiated by local failure sites that result in the formation of particle jets that extend ahead of the accelerating, largely intact, wafer core. In a circular tube the failure sites are uniformly distributed along the wafer circumference. In a square channel, the failure sites, and the subsequent particle jets, initially form at the corners due to the enhanced shear. The wafer breakup subsequently spreads to the edges forming a highly non-uniform particle cloud.

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Metalized heterogeneous detonation and dense reactive particle flow

Cited by 11 publications

References 5 publications

Large-scale spray detonation and related particle jetting instability phenomenon

Large-scale spray detonation and related particle jetting instability phenomenon

Numerical simulation of one-dimensional aluminum particle–air detonation with realistic heat capacities

Dense Particle Cloud Dispersion by a Shock Wave

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