The radiation properties of burning clouds of metal dust. 3. Modification of the emission spectrum

Abstract

In this work we studied the emission spectra of the combustion products of low-volume dust clouds (V = 5 L) from aluminum (ASD-4), as well as clouds from mixed compositions of aluminum with inorganic powdery oxidizing agents (NaNO3, NaCl, Na2CO3·10H2O, Sr(NO3)2, Ba(NO3)2, KNO3, CuSO4, CuSO4·10H2O) and combustible (B, AlB2, Cu). This article discusses the possibilities of purposeful modification of the emission spectrum of the base composition using various inert and optically active dispersed additives that shift the maximum of the emission spectrum of the fuel composition to the region of longer waves or cause a local change in the emission spectrum in the corresponding spectral regions.
 In the course of the experiments, it was revealed that the introduction of additives into the basic composition of dispersed fuel does not significantly change the dynamic characteristics of the suspension. However, the additives lead to a decrease in temperature (by about 100–200°K in the presence of an additive up to 25% by weight) and to a corresponding shift in the maximum of the radiation spectrum.
 The possibility of a significant local modification of the spectrum in the yellow region with the help of inorganic additives to the fuel of sodium salts with a low decomposition temperature (additives Na2CO3·10H2O) was shown experimentally. Boron additives and boron compounds (B, AlB2) leads to a significant increase in the luminosity of the flame in the green region of the spectrum with a maximum radiation in the range Δλ = 530 ÷ 580 nm. The article presents the lighting characteristics (luminous intensity, light sum) of large clouds (V ≥ 10 m3) of mixed compositions based on PAP-2 aluminum powder.
 It was found that the introduction of inorganic additives to the base fuel does not lead to a noticeable change in the lighting characteristics, but somewhat increases the time of the cloud glow both in the visible and infrared parts of the spectrum.