The radiative characteristics of the condensed phase in the combustion zone of a laminar diffusion aluminum particle flame were studied by spectral methods. It is shown that the weak dependence of the condensed-phase temperature on the mass concentration of the fuel was due to heat losses, which increased strongly with increasing mass concentration and reached 20% of the total heat release. Strong temperature dependence of the imaginary part of the complex refractive index was obtained, which ultimately limited the flame front temperature. In practice, this should lead to a dependence of the heat losses on the condensed phase temperature stronger than T 4 . The dependence of the imaginary part of the complex refractive index on the wavelength was determined experimentally at the combustion temperature.

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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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