Optical constants of Al2O3 smoke in propellant flames

Absorption Coefficient of Molten Aluminum Oxide in Semitransparent Spectral Range

“…In fact, the use of analytical approximation of dependencies   f (, T), significantly simplifies calculating of radiative, radiative-conductive and radiative-convective heat transfer in molten Al 2 O 3 . Among the first attempts in this direction was the work the results of which are presented in reference (Parry & Brewster, 1991). In this work, in addition to finding of analytical dependence f(,T), also experimental investigation is carried out focusing on particles produced as a result of burning of aluminized solid propellants in conditions similar to the conditions of burning in a real rocket motor.…”

“…And even the calculation results made on the basis of the expressions received in the two works (Parry & Brewster, 1991) and (Kuz'min, 2004), where for the approximation were used the results for molten droplets of solid propellant combustion products, there was a divergence of more than one order. This suggests for a joint analysis of all available data on the absorption coefficient of molten Al 2 O 3 , regardless of whether analytical description of the obtained dependences is available or not.…”

“…Based on the model of two oscillators with characteristical wavelengths of 0.1107 µm and 17.57 µm, taken on the basis of the results of earlier published works on dispersion analysis of Al 2 O 3 single crystal at room temperature (Gervais, 1991;Tropf & Thomas, 1998), and on traditional fitting of approximation dependences using the least squares method, there are found expressions for a number of empirical coefficients, which characterize the dispersion parameters for a real and imaginary part of dielectric permittivity. In reference (Parry & Brewster, 1991) the results of calculation of  and n of molten Al 2 O 3 in the wavelengths ranging from 0.5 µm to 5 µm, at temperatures of 2320, 2500, 2680, 2800 and 3000 K are presented. Figure 1 shows the calculation results for the dependence of the absorption coefficient  on the wavelength at these temperatures, made on the basis of data of reference (Parry & Brewster, 1991).…”

“…In reference (Parry & Brewster, 1991) the results of calculation of  and n of molten Al 2 O 3 in the wavelengths ranging from 0.5 µm to 5 µm, at temperatures of 2320, 2500, 2680, 2800 and 3000 K are presented. Figure 1 shows the calculation results for the dependence of the absorption coefficient  on the wavelength at these temperatures, made on the basis of data of reference (Parry & Brewster, 1991). In reference (Anfimov, Karabadjak, Khmelinin, Plastinin, & Rodionov, 1993), the authors, based on the results of their own measurements in the range from 0.2 µm to 7 µm, present empirical expressions for four items of the absorption index of molten Al 2 O 3 :  0  1  2  3 .…”

“…As a result, 0.0060.004 for both wavelengths, and n 1 =1.65 and n 2 =1.64, respectively. On the basis of these data, and using data of other researchers (the results of Mularz & Yuen (1972); information provided to the authors of reference (Parry & Brewster, 1991) by B. Reed in private, which presents the expression describing the dependency of  particles, collected from a rocket plume and heated in a shock tube, on temperature and wavelength in the range from 1.7 µm to 4.5 µm, and also G. Gal and H. Kirch's data for temperature of 3000 К in the range from 0.5 µm to 5 µm, which Parry and Brewster (1991) consider as a simple extrapolation from a solid phase), a dispersion analysis is made using the classical dispersion theory. Based on the model of two oscillators with characteristical wavelengths of 0.1107 µm and 17.57 µm, taken on the basis of the results of earlier published works on dispersion analysis of Al 2 O 3 single crystal at room temperature (Gervais, 1991;Tropf & Thomas, 1998), and on traditional fitting of approximation dependences using the least squares method, there are found expressions for a number of empirical coefficients, which characterize the dispersion parameters for a real and imaginary part of dielectric permittivity.…”