Optimal Pyrotechnic Illuminants: Part 1. Red Colour

ABSTRACT Several optimisation criteria for red pyrotechnic illuminants consisting of magnesium, strontium nitrate, polyvinyl chloride and chlorinated paraffin were evaluated. The optimisation criteria are based on different a priori physical assumptions intended to produce the desired optimum. Three of these criteria proved the most effective and thus more correct than the rest producing the best possible measured properties of the compositions. Maximising the ratio of main colorant molality to the molality ( b ) of solid species in the combustion products max( b (SrCl)/ b (condensed)) maximises the excitation purity. The highest specific luminous intensity (cd s/g) can be obtained by maximising the product of the main colorant molality and the adiabatic flame temperature, i.e., max(( b (SrCl) * T ). The longest dominant wavelength is obtained by maximising T * b (SrCl)/ b (condensed). The thermodynamic calculations were carried out using NASA CEA2 thermochemical code and the optimization procedure was implemented in Matlab. The excitation purity could be improved from 80% to 91% (14% improvement), the specific luminous intensity increased from 17.3 to 21.4 kcds/g (24% improvement) and the dominant wavelength from 607 to 615 nm compared to a baseline composition reported in literature. The excitation purity of every type of compositions reported in literature could be considerably improved by applying the first optimization target mentioned above. Compositions based on other fuels than magnesium taken from literature could also be improved. The results were verified experimentally.