On the Burning of Single Drops of Monopropellants

Citation

Kiley, Donald Walter (1955) On the Burning of Single Drops of Monopropellants. Engineer's thesis, California Institute of Technology. doi:10.7907/33WQ-4M23. https://resolver.caltech.edu/CaltechETD:etd-12032003-112346

Abstract

A simplified theoretical treatment has been developed for the burning of single drops of monopropellants. Evaporation constants and the ratios of flame to droplet radii have been calculated for the following monopropellants burning in an inert atmosphere: hydrogen peroxide, nitromethane, hydrazine, ethylene oxide, ozone and nitrous oxide. Compared with the results of similar calculations for fuels burning in air, much smaller flame radii were obtained, while the evaporation constants were found to fall in the same range as before. Attempts at burning single droplets of monopropellants (e.g. hydrazine and nitromethane) in a nitrogen atmosphere were unsuccessful. Monopropellant droplets burning stably in air were found to extinguish if the oxygen was removed during burning. These experimental findings probably reflect the well-known difficulties encountered in monopropellant operation, which is usually successful only if a suitable reaction catalyst is available. The applicability of calculated monopropellant burning rates to practical cases cannot be assessed at this time. Single droplets of hydrazine and nitromethane were burnt in air and evaporation constants determined experimentally. The measured rate for nitromethane was found to be in good agreement with calculated results for heterogeneous burning of fuel droplets in air. The measured rate for hydrazine was found to be considerably higher than the value calculated for fuel droplets burning in air or for monopropellant droplets burning in an inert atmosphere. This latter result probably indicates that the assumption of a diffusion flame for the burning of hydrazine in air is not valid, i.e., the hydrazine decomposes throughout the region between the liquid surface and the "flame surface" rather than reacting instantaneously at the "flame surface".

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