Combustion Synthesis and Investigation of Metal Oxide Nanopowders Properties

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.

Section: Introductionmentioning

confidence: 99%

Spectral studies of the gas component of an aluminum dust flame

Poletaev

Florko

2008

“…Metal vapor and suboxides are additionally oxidized near the particle surface (in the combustion zone). Gas-phase combustion of metals with a high boiling point (Zr, Ti, and Fe) has been experimentally observed in premixed flames with an excess of oxidizer and an oxygen content in the gas suspension above 40% [1,2,15].…”

Section: Structure Of the Combustion Zone Of The Metal Dust Flamementioning

confidence: 99%

Formation of condensed combustion products in metal dust flames: Nucleation stage

Poletaev

2015

The nucleation of the ionized combustion products of small (d 10 ≈ 5 μm) particles of Al, Mg, Zr, Fe, and Ti under laminar dust flame conditions at atmospheric pressure is considered in an isothermal approximation. It is shown that under conditions close to the experimental ones, the condensation of the products of gas-phase combustion of these metals is "rapid." Description of the "rapid" nucleation regime requires a nonstationary approach and knowledge of the kinetics of nucleation of the condensed phase and does not need a detailed analysis of the influence of environmental parameters on the free energy of formation of small nuclei. It is shown that the characteristic nucleation time of the gas-phase combustion products of metal particles is several orders of magnitude smaller than the residence time of the products in the combustion zone of the flame dust. This allows coagulation to be considered as the basic process which determines the degree of dispersion of primary particles of the metal combustion products.

“…4). The values of f * can be estimated from measurements of the combustion temperatures of suspension particles (Table 1) [5,[26][27][28] and data on the width of the combustion zone of the propagating flame [25,27]. 6 As is evident from Fig.…”

Section: Flame Propagationmentioning

confidence: 99%

“…The problem of oxidizer burnout for disperse-fuel combustion was considered in detail in [28][29][30][31][32]. Using an isothermal approximation, the authors showed that a decrease in the oxygen content in the oxidizing gas during diffusion combustion of suspension particles results in a marked increase in the burning time and a decrease in the combustion temperature of the suspension compared to single-particle combustion.…”

Section: Overall Combustion Of Particle-gas Suspensionsmentioning

confidence: 99%

“…Such flames are of interest both as independent structures and as objects that allow one to study the combustion mechanisms of gas suspensions of metal particles in oxygen-containing media, the structures of combustion zones around the particles, the optical characteristics of burning metals, and the mechanisms of formation and growth of condensed-phase combustion products [26,28,37]. In addition, such flames can serve as productive sources of promising nanodisperse oxide materials, which under certain combustion conditions of gaseous suspension sprays can be condensed combustion products of metal particles.…”

Section: Laminar Diffusive Two-phase Flamementioning

confidence: 99%

See 1 more Smart Citation

Ignition and Combustion of Dust-Gas Suspensions

Zolotko

Vovchuk

Шевчук

et al. 2005

Self Cite

The ignition and combustion of dust-gas suspensions are considered. It is shown that the ability of these systems to accumulate heat is determined not only by their kinetic and thermal properties but also by the relation between their reaction surface and the heat-removal surface (f ). Experimental information on flame temperatures, ignition delays, and flame propagation over gas suspensions is processed using the parameter f , and the postulate on the stimulating role of the developed reaction surface in activating these processes is validated. It is shown that during overall burning, diffusion combustion of particles occurs only for rather small values of f . The ambiguous effect of the parameter f on the ignition and combustion processes leads to the necessity of optimizing the fuel size distribution and concentration for the effective operation of the power devices. The role of the macroparameters of two-phase flames of refractory metals in the synthesis of combustion nanoproducts is analyzed.