Experimental and theoretical study of the ignition and combustion of an aerosol of encapsulated aluminum particles

Yagodnikov, D. A.; Voronetskiĭ, A. V.

doi:10.1007/bf02671852

Cited by 44 publications

(14 citation statements)

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“…Note that an earlier mechanism postulated that particles ignite in oxidizing atmospheres due to thermal stresses, which cause the shell to crack and peel away from the surface, allowing oxidation of the bare Al core [4]. This mechanism does not account for intermetallic reactions between Ni and Al and is clearly inapplicable to ignition in inert atmospheres.…”

Section: Introductionmentioning

confidence: 96%

“…Prior studies [1,3] demonstrated that coating Al with Ni reduced particle agglomeration during propellant combustion. In addition, experiments [4] on the combustion of air/metal particle clouds have shown that the flame propagation velocity for Ni-coated Al particles is significantly higher than that for Al particles. It is thus expected that the utilization of Ni-coated Al particles will increase the efficiency of aluminized rocket propellants.…”

Section: Introductionmentioning

confidence: 96%

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Ignition mechanism of nickel-coated aluminum particles

Andrzejak¹,

Shafirovich²,

Varma³

2007

Combustion and Flame

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Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 96%

Ignition mechanism of nickel-coated aluminum particles

Andrzejak¹,

Shafirovich²,

Varma³

2007

Combustion and Flame

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“…Some coatings provided a significant increase in the velocity of flame propagation over the air suspensions. It was assumed [3] that the fluorine released by decomposition of the coatings acted as an additional oxidizer and reduced the protective properties of the aluminum oxide film on the particle surface. Both factors facilitate the ignition of the particles, resulting in an increase in the burning rate of the particle-air suspensions.…”

Section: Model Propellants: Formulations and Ingredientsmentioning

confidence: 99%

Ignition, combustion, and agglomeration of encapsulated aluminum particles in a composite solid propellant. II. Experimental studies of agglomeration

Глотов

Yagodnikov

Воробьев

et al. 2007

Combust Explos Shock Waves

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The combustion characteristics of propellants containing AP, HMX, an energetic binder, and aluminum particles with various polymer coatings are studied at pressures of 0.15 and 4.6 MPa. It is found that the coatings influence the burning rate, the particle size distribution of condensed combustion products, and the completeness of aluminum combustion. It is shown that the agglomeration can be reduced by using aluminum with fluorine-containing coatings. The application of some coatings results in a reduction in the mass of the agglomerates with an insignificant increase in their size. The greatest effect was achieved when using aluminum coated with (CH 2 CH CH 2 O) 2 Si[OCH 2 (CF 2 CF 2 ) 2 H] 2 [bis(allyloxy)-bis(2,2,3,3,4,4,5,5-octafluoropentyloxy)silane]. For this coating, a size reduction is also observed for micron-size oxide particles.

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“…But it is quite obvious that other reasons are also possible. For instance, a strong increase in oxidelayer permeability can arise if the layer becomes porous due to punctures and ruptures [7,8] or due to the formation of a system of capillaries and cavities, such that the fuel and the oxidizer come into direct contact, without the interference of the oxide layer interposed between them.…”

Section: Introductionmentioning

confidence: 99%

Metal-particle ignition and oxide-layer instability

Meinköhn

2006

Combust Explos Shock Waves

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The use of metals as high-energy fuel additives is generally compromised by the appearance of a strongly protective oxide layer that covers the fuel surface. The previous work concentrated on the elimination of the oxide layer by a global, symmetryconserving attack, using an admixture of aggressive chemical constituents in the ambient atmosphere, a strong flux of radiation, or strongly shearing gas flows designed to intensely strain the surface layer. This paper shows that symmetry breaking leads to a different approach to ignition. For a liquid oxide layer, destabilization can be obtained via the Marangoni effect associated with longitudinal surface stress, thus breaking the translational symmetry in longitudinal directions. The thermodynamic state of the layer is described in a thin-film model, which leads to a creeping-flow approximation. Ignition by way of the Marangoni effect is then shown to result from spreading of punctures and ruptures in the oxide layer, which is a prerequisite for layer thinning or even complete layer removal. Boron-particle ignition is selected to illustrate the theory, because the well-known difficulties with boron ignitability have greatly impaired the use of boron fuel in propulsion devices. It is shown that, for ambient temperatures below 1634 K, the oxide surface layer can be destabilized by way of punctures and ruptures, owing to the peculiar property of the boron oxide, namely, positive Marangoni numbers. Previous models of boron-particle ignition insisted on conservation of symmetry and expressly excluded the appearance of punctures and ruptures. Because of this constraint, a critical ambient temperature of 1900 K for boron ignition was obtained, so that the new value of 1634 K opens up a novel approach to ignition.

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Experimental and theoretical study of the ignition and combustion of an aerosol of encapsulated aluminum particles

Cited by 44 publications

References 1 publication

Ignition mechanism of nickel-coated aluminum particles

Ignition mechanism of nickel-coated aluminum particles

Ignition, combustion, and agglomeration of encapsulated aluminum particles in a composite solid propellant. II. Experimental studies of agglomeration

Metal-particle ignition and oxide-layer instability

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