Atmospheric combustion flame, absorption

Gaussian Laser Profile-Voigt Atom Profile. This case turns out to be a better approximation of our experimental situation, i.e., the laser FWHM is fairly broad compared to the absorption line width and the absorption profile of atoms in an atmospheric combustion flame is described by a Voigt profile. Here the laser is assumed to have a Gaussian spectral profile as well as a Gaussian atomic absorption profile. In this case, convolution of two Gaussian functions is still a Gaussian function. Evaluation of the ratio n2/nT, and the fluorescence radiance. Bp, allows determination of the half width of the fluorescence excitation profile, 6X... 

Measurements. Combustion temperatures of PETN, RDX Tetryl were measured at 20-100 atm in a constant-pressure bomb under a N2 atmosphere (Refs 2 3). The absorptivities of the PETN and Hexogen flames were 0.1-0.3 and that of the Tetryl flame 0.8-0.9. In all cases the flame absorptivity increased toward the surface of the charge. If secondary explosives are volatile, as noted by Belyaev... 

The midwave ambient atmosphere and pressure IR spectrum of a Mg/PTFE/Viton combustion flames is dominated by a strong carbon continuum superimposed from a series of molecular emitters such as H2O, HF and CO2 both in emission and absorption (Figure 9.33). As carbon dioxide emission is always partially absorbed by the cooler combustion gases, the typical so-called blue spike and red wing appear. At greater distances between flare and spectrometer, the absorption of radiation because of the atmospheric constituents becomes relevant as can be seen from the overall spectrum depicted in Figure 9.34, which has been recorded in 10 m distance to the flare. 

For this temperature and for the lower heating value of the fuel and the amount of combustion air, including excess chosen, compute the pseudo-flame temperature and plot this on the zero ordinate. Draw a straight line back through this point and the heat absorption value plotted on the curve until it intersects the line of atmospheric temperature (conventionally, 60°F). This will give the Btu per hr. per sq. ft. that must be released. Call this Qf. Then Qr/Qf is the fraction of the heat released per square foot per hour that is absorbed by radiation. 

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