Mechanisms of chemical suppression of rocket exhaust afterburning

Abstract

Methyl bromide, anhydrous ammonia, and phosphorus pentoxide were added to flat, laminar, opposed-jet diffusion flames of CH 4 -02- N2 and H2-co-o 2-N2. The 4000 cm-1 to 2000 cm-1 infrared flame emission spectra were scanned in non-overlapping increments of 0.33 mm width using a modified infrared absorption spectrometer with an external optical scanning system. Methyl bromide results show narrowing of the flame zone and an increase in maximum emission intensity. This is consistent with studies in the literature and validates the use of opposed-jet flames for evaluating additive effects. Ammonia results show inhibition occurring on the fuel side of the flames and acceleration occurring on the oxygen side. Phosphorus pentoxide results show behavior that is interpreted as resulting from non-equilibrium processes in the flames, which prevents drawing conclusions about phosphorus pentoxide effects on afterburning. The practicality of using these additives in solid propulsion systems is discussed.