Flames structure measurement of single, isolated aluminum particles burning in air

Bucher, P.; Yetter, Richard A.; Dryer, Frederick L.; Parr, T. P.; Hanson‐Parr, D. M.; Viceni, E.P.

doi:10.1016/s0082-0784(96)80012-9

Cited by 108 publications

(41 citation statements)

References 12 publications

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“…According to the data of Bucher et al [10], who used the method of induced fluorescence to determine the radial distribution of AlO suboxide over the radius for Al particles of diameter 210 μm, the maximum concentration of suboxide was recorded at r/r p = 2.8 (r p is the particle radius), whereas the maximum concentration of condensed oxide Al 2 O 3 at r/r p = 3.5 (this is the visible radius of the combustion zone that is usually determined from photographs and cine films), and the maximum gas-phase temperature measured from the bands of AlO is within 5 < r/r p < 6. It is interesting that Bucher et al [10] obtained a nonzero AlO concentration on the surface of a burning droplet, which in [10] was attributed to the kinetic regime of consumption of this suboxide in the heterogeneous reaction.…”

Section: Spectral Studies Of the Combustion Zone Using The Molecular mentioning

confidence: 99%

“…For this reaction, the rate constant is K = 9.76·10 13 exp(−80/T g ) cm 3 /(mole · sec) [10] and, hence, the characteristic reaction time is τ r ≈ 10 −8 sec at a combustion temperature T g = 3200 K. For fine particles, this time is comparable to the characteristic diffusion time of the reactants τ d = r 2 z /D. Indeed, assuming that the radius of the vapor-phase zone of aluminum combustion is r z = 3r p , we have τ d ≈ 10 −8 sec.…”

Section: Spectral Studies Of the Combustion Zone Using The Molecular mentioning

confidence: 99%

“…[9][10][11]. A more convenient tool for these purposes is the use of steady-state laminar dust flames.…”

Section: Introductionmentioning

confidence: 99%

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Spectral studies of the gas component of an aluminum dust flame

Poletaev

Florko

2008

Combust Explos Shock Waves

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The combustion zone of a steady-state laminar diffusion flame of aluminum particles of diameter 4.8 µm at a metal weight percentage of 0.4 kg/m 3 was studied by atomic and molecular emission spectra. Absolute measurements of the luminosity of the sequence of bands due to AlO made it possible to determine the gas-phase temperature (3200±100 K) and the AlO vapor concentration [(1.5 ± 0.5) · 10 21 m −3 ] at the flame front. From an analysis of measurement data on the intensity and contour of the resonance line of aluminum, it is concluded that the metal particles burn individually to form microflames. Estimates were made of the size of the combustion zone of an individual particle and the gas-phase temperature near a particle (3150 ± 200 K). Some features of the combustion mechanism of fine aluminum particles in the dust flame are analyzed. The capabilities of spectral methods for studying the thermal and concentration structures of dust flames are demonstrated.

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Section: Spectral Studies Of the Combustion Zone Using The Molecular mentioning

confidence: 99%

Section: Spectral Studies Of the Combustion Zone Using The Molecular mentioning

confidence: 99%

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Spectral studies of the gas component of an aluminum dust flame

Poletaev

Florko

2008

Combust Explos Shock Waves

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“…There was some question as to whether aluminum combustion is purely diffusion-controlled or if kinetics can also have some influence [7,17]. Experiments also showed that the flame-zone thickness, which is also an indicator of the pace of the kinetics, varies with each oxidizer [20][21][22]. In the case of CO as the oxidizer, combustion can be heterogeneous [18], which may lead to a kinetically controlled process as surface reactions are expected to be slower than gas-phase reactions.…”

Section: Aluminum-combustion Mechanismmentioning

confidence: 99%

Numerical Simulation of Single Aluminum Particle Combustion (Review)

Beckstead

Liang

Pudduppakkam

2005

Combust Explos Shock Waves

144

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A two-dimensional, unsteady-state, kinetic-diffusion-vaporization-controlled numerical model for aluminum particle combustion is presented. The model solves the conservation equations, while accounting for species generation and destruction with a 15-reaction kinetic mechanism. Two of the major phenomena that differentiate aluminum combustion from hydrocarbon-droplet combustion, namely, condensation of the aluminum-oxide product and subsequent deposition of part of the condensed oxide onto the particle, are accounted for in detail with a submodel for each phenomenon. The effect of the oxide cap in the distortion of the species and temperature profiles around the particle is included into the model. The results obtained from the model, which include two-dimensional species and temperature profiles, are analyzed and compared with experimental data. The combustion process is found to approach a diffusion-controlled process for the oxidizers (O 2 , CO 2 , and H 2 O) and conditions treated. The flame-zone location and thickness are found to vary with the oxidizer. The result shows that the exponent of the particle-diameter dependence of the burning time is not a constant and changes from ≈1.2 for smaller-diameter particles to ≈1.9 for larger-diameter particles. Owing to deposition of the aluminum oxide onto the particle surface, the particle velocity oscillates. The effect of pressure is analyzed for a few oxidizers. Key words: aluminum particle, two-dimensional unsteady-state numerical model, kinetic mechanism, effect of the nature of the gaseous oxidizer, condensed oxide, oxide dissociation, oxide cap, burning time, species and temperature fields INTRODUCTIONAluminum has been added to propellants for many years as an extra energy source for the propellant. Thus, research on the combustion mechanism of burning aluminum has been an ongoing effort. A very significant effort was expended in the 1960s and 1970s shortly after the effects of aluminum were first conceived. In an early study, Glassman [1] and Brzustowski and Glassman [2] recognized that metal combustion would be analogous to hydrocarbon-droplet combustion, that the D 2 law ought to be applied, and that ignition and combustion ought to depend on the melting and boiling points of the metal and the oxide. Glassman speculated that ig-

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“…AlO has been observed by Yuasa et al in Al/CO 2 experiments using AlO emission spectroscopy in the visible range [30], by Bucher et al [31] using AlO laser-induced fluorescence (LIF), by Driscoll et al [32] using AlO emission spectroscopy, and by Vanpée et al [33] in trimethylaluminum-oxygen flames, among others. AlO has been identified mass spectrometrically to be a vapor species above solid alumina [34].…”

Section: Aluminum Oxidesmentioning

confidence: 96%

Thermochemistry of aluminum species for combustion modeling from Ab Initio molecular orbital calculations

Swihart

Catoire

2000

Combustion and Flame

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High accuracy ab initio methods for computational thermochemistry have been applied to aluminum compounds expected to be present during combustion of aluminum particles. The computed enthalpies of formation at 298.15 K agree well with experimental values from the literature for AlCl, AlCl 3 , AlO, AlOAl, linear OAlO, planar Al 2 O 2 , AlOH, AlH, and AlN. The agreement is fair for AlCl 2 . Major revisions to the recommended thermochemistry must be considered for OAlCl, OAlH, OAlOH, and AlC. This is not surprising since the thermodynamic data for OAlCl, OAlH, OAlOH, and AlC are given in the literature as rough estimates. Calculated thermochemical data are also presented for several species never studied experimentally, including AlH 2 , AlH 3 , AlOO, cyclic-AlO 2 , linear AlOAlO, AlHCl, AlHCl 2 , and others. Based on the performance of the CBS-Q and G2 methods observed in other systems, the calculated enthalpies of formation would be expected to be accurate to within Ϯ1 to 2 kcal mol Ϫ1 . However, relatively large differences between the results from the CBS-Q and G2 methods for the aluminum oxides indicate that the uncertainties are slightly larger for these compounds. The thermochemistry proposed here is shown to predict substantially different equilibrium composition from the thermochemistry previously available in the literature.

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Flames structure measurement of single, isolated aluminum particles burning in air

Cited by 108 publications

References 12 publications

Spectral studies of the gas component of an aluminum dust flame

Spectral studies of the gas component of an aluminum dust flame

Numerical Simulation of Single Aluminum Particle Combustion (Review)

Thermochemistry of aluminum species for combustion modeling from Ab Initio molecular orbital calculations

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